Psych 161 Midterm

Neuroplasticity

-(aka brain plasticity/cortical plasticity) -changes that occur in the neural pathways or synapses of the brain as a result of experience -refers to how the brain adapts to different types of experience or input -adaptation is really important because some developmentalists argue that in fact we never actually mature instead we adapt and the distinction in that is that maturity suggests there is some kind of blueprint that you are following over the course of your life - that every single person will have some particular milestons (walking, puberty) but the idea of adaptation is important because that means you in particular adapt to your environment -and maybe that's a better characterization of neuroplasticity - that you are responding and changing because of what your environment gives you

The Importance of Time and Timing in Bain Development

-Absolute time that a neural event occurs -Days after conception -Days after birth -Time relative to other events -Development occurs as a cascade of events -One event may influence those that follow but not precede it. -We have discussed today how the processes that happen in utero are pretty well prescribed in that they happen at a particular time in development - we know down to particular weeks when migration happens and things like that -But it goes without saying but worth pointing out that timing is really important during development - that is that when something happens in prenatal development has consequences for the developing fetus -So there are two ways we can think about time: days after conception or days after birth -But there is also time relative to other events -So for instance if you the mother has some major trauma happen to her when she is pregnant that trauma wont have the same effect if the fetus is 8 months along vs. if its 4 weeks along because the development that is happening during those two distinct times is very different -At 4 weeks we are still building the heart and all the really basic things where as at 8 months that baby is much more robust and it has already passed through a lot of vulnerability and so there has been a lot of study examining how the timing of particular events affects brain development

Allostasis and Allostatic Load

-Allostasis: psychological and physiological adaptation in stressful situations -Helps maintain homeostasis -Maintains "stability through change" -good consequence of stress -Allostatic load: the physiological costs of chronic exposure to fluctuating or heightened neural or neuroendocrine response that results from repeated or chronic stress -bad consequence of stress -Allostasis is the adaptive side of stress that is referring to the fact that you have a stress response in a threatening or potentially threatening situation your body is bound to respond -So this is a good consequence of stress -Allostatic load refers to all the costs ive already referred to - that is associated with having too much stress or having the stress response being too sensitive or not shutting off properly -And so this allostatic load is of concern when thinking about plasticity because the allostatic load is so powerful that it can influence the neural plasticity in the developing organism

Characteristics of a systems approach

-An appreciation that the nature of life (living beings) is dynamic (i.e. development is ongoing throughout life) -Development is hierarchical -Phenotypes can emerge from a complex and dynamic (ongoing) interplay of factors -The "Individual" constructs their phenotypes from an already existing developmental history

How can lab animals help us understand stress effects in humans?

-Animal models provide the opportunity, usually not available in humans, for examination of stress effects at the cellular level

Phase 5

-Begins following puberty through adult years -Experience-dependent mechanisms -Loss of synapses around puberty may be related to hormonal changes -Process of elimination and pruning and this continues through college and the mid-20s as we make our own synaptic landscape based on experiences that are specific to us -It says experience dependent but I think its also experience expectant -For the reasons I said before in that expectant it happens in all of our species - in that we all undergo puberty and that process triggers a lot of other processes like pruning but its dependent in that the timing is not the same across everyone

Ectoderm

-Central Nervous System (Brain and Spinal Cord) -Peripheral Nervous System -Skin -Hair -Nails -The ectoderm is what we are focused on that becomes a lot of things the brain, the spinal cord, the peripheral nervous system, the skin, the nails, the hair - they all come from the same place -And in particular the skin and hair are very similar to one another -The same cells that give rise to skin in this stage of development are the same cells that give rise to skin now as adults

First Trimester (Embryonic Period)

-Certain hormones and organs are only produced during pregnancy -Hormone that maintains uterine lining (used for pregnancy tests) -Placenta: nutrients pass from mother to embryo -Allows teratogens (viruses, medicine, drugs) to pass through -Embryo is particularly vulnerable during weeks 3-9 to exposure of teratogens -Ex horomone that maintains uterine lining this is what tells you you are pregnant when you take a pregnancy test only happens during pregnancy - there is no reason for us to happen any other time -The placenta is an organ that is only in the service of the developing embryo and its how the mother feeds the embryo and how the embryo gets nutrients -This is another example - first example was how we crawl and we stop crawling because we start walking - of how development evolves -The placenta has to develop - the body exerts resources to develop the placenta but then it has to dissolve also because we dont need placenta after they are actually quite heavy - it wouldnt make sense to always have a placenta if you werent pregnant and so development is very smart this way in that it recruits and builds organs and resources it needs but then gets rid of them when they actually start to become burdensome

Phase 4

-Childhood years (varies by region; Visual cortex: 2-3 years; PFC: through adolescence) -Experience-expectant and experience-dependent mechanisms -Extended period of synaptic fine-tuning

Stress in Adults: the effects of traumatic stress

-Decreased hippocampal volume -Memory deficits -Increased glucocorticoids

Stress in Adults

-Decreases neurogenesis -Hippocampal volume loss -Effects of stress on adult brain are reversible -Similar to younger animals and developing animals the mechanisms are the same -Stress decreases neurogenesis which eventually is manifested in smaller hippocampal volume in humans measured with fMRI -Whats interesting is that even if this is not developmental plasticity the effects of stress in the adult brain can also be reversible - obviously it depends the kind of stress or the duration of the stressor but it is interesting that if it is an acute or discrete stressor those affects can be reversed -Chronic stress reduces neurogenesis in rodent brain (hippocampus) -Note: BrdU is a marker of new cells -This is just to remind you that chronic stress reduces neurogenesis in hippocampus So these are data from animal models where they measured the number of BrdU labeled neurons (BrdU is a measure of neurogenesis) and basically this is showing you that there is less neurogenesis in the stressed out animal compared to the control animal -Most human adults studies have focused on proxies of stress to examine its effects on the brain -Low self-esteem -Mental disorders/psychopathology -Post Traumatic Stress Disorder -Childhood abuse -Most generally find decreased hippocampal volume and elevated stress hormones -In adults its rather challenging to study neurogenesis and the way most human adult studies operated is they will measure proxies of stress -For instance people who have low self esteem are thought to have high levels of stress - so that means high levels of circulating cortisol -People who suffer from some types of psychopathology have also higher evidence of a stress response Individuals who suffer from PTSD whatever the event that caused the PTSD is not important but whats important is that if you are a person with PTSD the stress response keeps getting mounted every single time and in that way your brain doesn't shut off the response even though the threat is no longer present -And finally people who suffered from childhood abuse also have chronic stress even though the abuse is no longer going on that abuse was enough to set the stage for a chronic stress response throughout their whole lives -And generally what these studies find is that similar to the rodent study -I just showed you that there is decreased hippocampal volume in these people - that whether its self-esteem or PTSD or whatever it is there is a consistent finding of lower hippocampal volume and in some cases that is also associated with worse performance on cognitive tasks and learning tasks and things like that

Summary

-Development is the study of change -Change occurs as a product of gene-environment interactions -Development is an agent in the product -Thelan emphasizes development as a dynamic system -"Making something more from something less" -Development is an emergent product -i.e. not laid out beforehand

Inner cell mass

-Embryonic stage: endoderm, mesoderm, ectoderm -Undifferentiated: final fate not yet determined -Induction: process of transforming undifferentiated tissue

Prenatal Stress

-Environmental Toxins -Maternal Stress -Deprivation of nutrients/protective prenatal environment -But even in before early childhood there are a lot of stressors that are getting under the skin of the unborn child such as environmental toxins (like exposure to radiation), maternal stress (if the mother is having a very stressful pregnancy either based on the pregnancy or what is going on in her own life - her hormones will cross the brain barrier and get under the skin of the developing fetus), and also what can be stressful to the developing organism are deprivation of basic needs and that's certainly true throughout life - that if you get deprivation of nutrients or later in life if you have deprivation of sleep for instance those can all serve as physiological issues for the body because its not getting the resources that it needs -And so if there is stress that is exerpienced pre-natally these stressors are said to have programming effects

Stress in Adolescence

-Evidence to suggest that the adolescent brain is more susceptible to stressors than in adulthood. -Prolonged stress response in adolescent rats compared to adult rats -A lot happens right after puberty and one of the things that happens is you have a release of hormones - sex hormones - but there is a hypothesis that stress hormones change and the amount that is released after a stressor changes after puberty and the reason for that is because in adolescent animals and humans the adolescent seems to have a prolonged stress response that is in response to the same stressor the stress response seems to be amplified when people are adolescents or when animals are juveniles

Synaptogenesis: Overproduction, eliminating, and strengthening

-Ex. think back to your first year in college -You show up to the dorms and there are a lot of people who live in the dorms -Early on you kind of form a lot of weak connections - you kind of have a big catch all because you want friends but all of those friends wont necessarily be best friends for life - they may be someone who lives down the hall or lives in your dorm and you are happy to have them but you don't know where that relationship is going so you don't invest as much as you maybe one day will with some of these people -So the connections are rather weak and that's similar to the overproduction that happens right around birth -Connections are weak but you have a lot of them -In mid-college you start to get rid of some people and you start to strengthen the ones that are more meaningful -By graduation you have even fewer friends but those connections are pretty rock solid - you have some really lifelong friends -These are people that you have invested in - the relationship has become stronger and the only reason you could have strengthened these connections is because across the time in college you eliminated some of these other ones -If you hadnt let some of these connections go you wouldn't have had the time or energy to invest in the ones you found most meaningful and thats the same thing that happens in the synaptogenesis: overproduction and stabilizing and then eliminating -Once you get to my age you have very few friends but they are very strong because you no longer have time to see these people but the ones you have is super strong like you depend on that person a lot but you have stability -So stability comes at the extense of an expanded network -The same thing happens in synaptogenesis and so the main sequence is overproduction, elimination, and then strengthening

Developmental plasticity

-Experience influences the basic architecture of the brain (i.e. how the brain is going to be organized) -in developmental plasticity - in other words plasticity that happens in an organism that is still undergoing a lot of change that is still setting itself up -So that influences how the brain is going to be set up -If you experience stress when you are undergoing development that stress itself is going to become a part of how your brain will develop -Ex. you are building a house from the ground up - that is developmental plasticity sets all the things in place - all the processes that will influence everything else in life -Whereas adult plasticity experience influences an existing architecture of the brain - that is whenever you learn a new skill such as playing an instrument as an adult that new information has to get incorporated within all the other information in your brain so when you learn a new language as an adult the new language synapses have to get incorporated into your language region which already has another language that it is mostly representing -If you learn farsi when you are an adult and you are a native english speaker then the new language learning has to work within the confines of what is already existing in there - already existing neural networks -Coming back to this analogy - adult plasticity rather than building a house from the ground up its kind of like a house remodel where the new addition has to be working within the context of the already existing structure -Alterations to the Auditory and Visual Systems during development usually alters function (e.g. vision)

Adult Plasticity

-Experience influences the existing architecture of the brain (i.e. brain is reorganized to incorporate additions/deletions) -Expertise and training influence brain function (e.g. somatosensory cortex is changed in musicians) -Somatosensory cortex critical for finger movements -One example of how we know aquiring new information as an adult does in fact change the brain This is evidence for adult plasticity They took a group of musicians and non musicians and put them in an MRI and they showed them pictures of either musical instruments or control objects -And what they found is in musicians (in black) they have greater activation in auditory cortex when they are viewing pictures of musical instruments -And what that tells us is that their auditory cortex over time - over the experience they have had as being musicians - have led their auditory cortex to be more sensitive to objects that remind them of music -Their brains are distinct from those of non-musicians on this very particular skill which is music -Greater activation in temporal gyrus (auditory cortex) when viewing pictures of musical instruments in the musicians -Similarly when they listen to musical sounds - people who were musicians had greater activation in the same region (auditory cortex) and that's because their brain is more sensitized to this auditory information -That's just another example of plasticity -The point here is that if you learn something as an adult its much more challenging for the brain to incorporate that information if you already have a pre-existing notion of how something works - if you have already had been playing the violin your whole life and then you switched to piano then your brain can still learn how to play the piano but it might be even more restricted - its stuck on this other musical instrument -Greater activation in temporal gyrus (auditory cortex) in response to musical sounds in the musicians

Inside-out migration

-First we have these blue cells - are the new cells - then we have the green cells which are even newer than the blue cells and then we have the yellow cells which are newer then both of the other neurons -so we can see that the yellow cells were born down at the bottom but they simply moved up past the other neurons -This is inside out migration - that's how the cortex gets developed

Two types of genetic information

-Gene pool (species-related characteristics) -Genetic information from the human species (e.g. patterns of motor behavior such as walking upright, brain size and body structure) -Ancestry -Hair color, skin color, blood type, etc -Specific to each individual -Make up only 0.1% of all your DNA but account for all of the individual variability -The first genetic information is the gene pool -And this is referring to the species-related characteristics - things that are relevant to all members of the species -And this could be patterns of motor behavior such as walking, generally we all have brain size of a certain range that is standard as well body structure that is standard -The second type of genetic information that you get when you are a developing embryo is from your ancestors so this is more specific to your family -What hair color, skin color, blood type you are going to have - those are all more individual type of genetic information -And that is specific to each individual - people who are twins have more genetic similarity in certain ways but in general its specific to each individual -Whats interesting about this latter type of genetic information is that it only makes up a very small percentage of your overall DNA - only about 0.1% of your DNA is specific to you - only .1% of your DNA comes from your mom and your dad -However almost all of that individual variation accounts for that individual variability that we see -When we have the understanding that everyone is different - everyone processes emotional information in a different way - that makes you you - that makes you an individual but it only comes from about .1% of your DNA -And the reason is because it would be challenging for the developing organism to have to reinvent where to put the individual in the brain - to have to reinvent which steps in development come next - all of that is very highly organized

Rate of Development

-Genes help regulate the pace of maturation -Genes signal the onset of growth spurts, teeth, puberty and menopause -Motor skills, intellectual capacity and timing of physical maturation are under strong genetic influence -Interacts with environment to promote development -Genes help regulate the pace of maturation - how does the body know when to move on to the next phase of development? -How does the body know to become more mature? -In part that might happen because of the experience you are having but its fascinating to think about how genes can signal the onset of growth spurts for instance -Its unknown which particular genes are involved in triggering growth spurts or puberty or these really massive important biological changes that all humans undergo - it's the genes that unknown to us exactly the combination of exactly how that happens are the ones that trigger those rates of development -Similarly motor skills and physical maturation are under the strong genetic influence -However it interacts with the environment to promote development - so you may be aware that there is a range in which people attain puberty typically between for girls about 10-14 when they undergo the biological processes of puberty - but in some populations thats sped up and in some populations that is slower -So in girls who live in very stressful environments it seems that they experience puberty earlier -Whereas girls who are very physically active - their puberty seems to be delayed -And so that is an example of how the environment somehow talks to the genes that were already going to trigger the process of puberty

Summary

-Genetic factors are critically involved in both trait characteristics and timing of development (they contribute to variability in the phenotypes we observed at birth, childhood, and later on) -Each trimester of pregnancy is unique -All organs develop along unique timescales (all the organs are not happening at the same time - I want you to keep that in mind as we think about how the different cognitive processes come along too - not all cognitive processes and abilities come at the same time - we learn to walk before we learn to have complex decision making for instance) -Brain development begins right after conception and continues through mid-20s -Genetic and environmental influences alter course of brain development -Events and processes occur in a particular sequence and at particular times -When a particular event occurs in development can influence long-term outcomes -Last point: when an event happens in development it can have long term effects that are not immediately observable and that becomes relevant for psychopathology - a lot of psychopathology doesnt emerge till the adolescent years and so researchers wonder was there an insult that happened early in development that somehow stayed dormant but then something about adolescence like puberty for instance triggers the particular phenotype that they observed not until that later age

Prenatal Development

-Genetic factors guide the tempo of growth and the emergence of individual characteristics -The psychosocial environment provides both resources for and challenges to healthy development -There are two things that regulate all of development and its certainly true during the prenatal time -First there are genetic factors that guide the tempo and growth of individual characteristics -In general that refers to things that are inheritable that come from your mom and your dad - but also genetic factors that have been passed on through successive generations because there are certain characteristics that all humans have so for instance all of us have in typical development have a pre-frontal cortex in the same place -All of us have generally certain brain regions that are located in a particular region of the brain and so that type of patterning comes from genetic factors -The second thing that influences prenatal development is the psychosocial environment - this refers to generally the mothers health or the experiences that the mother is having at the time she is pregnant - certainly having a very stressful life experience during the time of pregnancy - will get under the skin of the developing fetus

Genotype/Phenotype

-Genotype: genetic information about a trait -Phenotype: the observed characteristics of the trait -A phenotype is like eye color - but in this context for this class a phenotype is also the expression of behavior and that may vary across development -It certainly varies across individuals and its not the case that people of a certain age for instance will all have the same phenotype -For instance - a 14 year old adolescent often takes a lot of risks but not all adolescences take risks - risk taking is a type of phenotype -And the reason all of this is important is because of how it contributes to variability in behavior and traits

Experience-expectant/Experience-dependent

-Greenough et al proposed a new classification to replace "sensitive period" -ive already introduced expectant by noting that - here when I said in the critical period a particular input like visual information is expected -Expected means that in our species our brain has come to expect particular pieces of information at particular windows of development

Disorders of Neuronal Migration

-Here is another point where things can go wrong because when development happens typically and follows the same pattern as all the other species we end up with these layers -However it's the case that some neurons don't get the message and they don't migrate to the place they need to migrate and so these are called disorders of neuronal migration -This image is a timelapsed image that is showing you similar to E 8.5 and E 10 that I was talking about before this is time 1, 2 and 3 and the neuron is making its way up that's normal that is typical -But there are cases where if particular genes are not turned on or off or the molecular signals don't work properly that everytime you measure the animal the neuron is at the same place -Meaning it is not moving up - it is not migrating to its appropriate location and eventually that leads to a host of different disorders - one that is perhaps most common because people with this disorder are viable meaning they are born But they have something called smooth brain or lissencephaly -In typical development there is a lot of folds but in this brain its very smooth because not all layers of the cortex reached their destination and that's because they also don't have as many neurons as they need to have to populate a typical brain

Better maternal care reduces stress response in pups

-Here the data im going to show you are from animal models -What they did was not only examine maternal seperation but they also examined variation in maternal care and found that the pups reared by moms that had a lot of good maternal care fared better in terms of their stress response -Those pups did much better then the pups whose moms didn't do much maternal care -So in rodents maternal care is measured by how much licking and grooming they do -What they do is they measure the stress response in the animals based on these categories -So they categorize them as either pups reared by mothers with good maternal care or pups with poor maternal care -And in white are the pups with the good maternal care -Black are those with poor maternal care -Maternal care here is licking and grooming -And what they find is that if they give them a stressor early on and then you measure the stress response - the pups with the good maternal care they do match the stress response - that's important because we need to know their stress response is working - stress can be useful but notice that their stress response isnt as high as the animals with poor maternal care and it decreases more quickly than the animals coming from the bad maternal care moms -So the better maternal care reduces the stress response in the pups If they mix the pups and put a pup from a poor maternal care mom with a mom with good maternal care it can reduce the affects of the poor maternal care -So that supports this idea of reversability and how important it is to know the extent to which these effects can be reversed - their data suggests that the environment makes a really big difference in that pups outcome regardless of whether their mom is naturally high or low on caregiving -This stressor here was three hours of seperation from the mom -So they separate them from 3 hours and then test them on the stress response

Does prenatal stress influence behavior in adulthood?

-Heres an example of that: stress does influence behavior in adulthood -Even if animal is prenatally stressed and you don't see the effects of stress early in life the effects may reoccur or emerge later - so for instance in this study they prenatally stressed rats -And they prenatally stressed them in various ways - in this case they put cat hair in the moms cage and that's very stressful - so the mom is stressed and in turn it stresses the babies out -So they prenatally stress the rats and they test them on a very simple learning test when the rats were 6 months, 15 months, and 21 months so different time points -And they had some controls - they had a control group of animals who were never stressed and another control group of animals on the graph (H) those animals were handled but not stressed -And here is what you find - at 6 months there is no evidence of the prenatal stress even in the animals that were prenatally stressed in black -Their performance is very similar to the animals that are not stressed out the same is true at 15 months - the critical piece of this graph is shown here at 21 months because now what you are seeing is the prenatally stressed rat performs significantly worse on this learning task than the rats that were not stressed -What this is telling us is that the prenatal stress doesn't have to have immediate effect we don't necessarily see the effects of stress right away it could take a long time before you start to observe the effects of the stress -And the reason this research has got a lot of attention is because it might serve as a model for psychopathology that doesn't emerge until people are in their teens or early 20's -A lot of psychopathology start to show when people are teenagers or after puberty -And so it could be the case that if stress has something to do with it maybe the effects of whatever the psychological disorder is are relatively dormant early in life and start to emerge once some other life change happens like puberty -So these data are evidence for what is called delayed effects - the phenomenon that the effects arent immediately obvious -Increased responsiveness to drugs of abuse -Prenatally stressed rats showed increased locomotor activity in response to amphetamine and greater self-administration of amphetamine -One more example of this: in humans there is an observation that some individuals that experience a lot of chronic stress early in their lives seem to be more susceptible to addiction or substance abuse disorders and to interogate this a little bit more there has been studies in animals and here again they find a very similar thing that animals that were prenatally stressed show higher rates of self administration of amphetamine -Here showed at the top line as compared to animals that were controlled and never experienced prenatal stress -And again these animals weren't tested immediately after they were born they were tested months later and this effect remains -One hypothesis for why this is is because stress hormones also act on lymbic regions that are responsible for reward sensitivity for addiction and early in life there is some interaction between this heightened stress response which later leads to greater sensitivity to drugs and abuse but that hasn't been supported empirically -Increased depression and anxiety-related symptoms -And finally animals that are prenatally stressed show increaesed depression and anxiety symptoms -So here again they had 3 groups of animals -Prenatally stressed under black -And the elevated plus-maze is a test often used in rodents to test anxiety -What you get is that if they spend less time active in the apparatus that they are more anxious -So more anxious are the animals down here and you can see there is significantly more anxiety in the prenatally stressed animals than in those that were never prenatally stressed -And indeed in humans again there is some evidence that prenatal or early postnatal stress individuals have higher overall anxiety and depression when they are older -does prenatal stress influence behavior in adulthood? -Yes -Stress experienced early in life will undoubtedly influence the individual later in life -In humans, prenatal stress is linked to: -Lower birthweight -Preterm delivery -Increased stress response in offspring -Increased rates of mental health issues in offspring -And all of these are associated with later health outcomes as the kid gets older

Enhanced neurogenesis in socially-enriched (EC) animals

-Heres in example of neurogenesis in these animals -So remember BrdU is a marker of new neurons -The Y axis here is showing you the number of BrdU labeled cells in the controlled animal and the enriched animal -So the controlled animal is really the isolated animals the enriched is the complex environment -At baseline both animals are generating a lot of new neurons - 4 weeks later - 4 weeks after they have either been isolated or enriched the enriched animals show significantly more new neuronal birth than the control animals even after just 4 weeks -These graphs are showing the same thing just in different areas of the hippocampus -GCL is the granule cell layer of the hippocampus and these asteriks denote the significant difference -And basically there is greater neurogenesis in the enriched environment animals -Heres just another example of how it effects performance so in this case the enriched animals are showing better performance especailly as time goes on where as the control animals are not having a performance that is as good as they are -And in part that's because they have fewer neurons but also if you are in an enriched environment you are getting exposure and practice and experience interacting with the mazes and all these other things that keep the neurons useful and functional whereas the animals in the bare cages don't have much to do in there so the neurons are not getting exposure and experience

Experience-Expectant

-If "expected" visual input is not received during the critical periods in development, alterations develop in: -Behavior (e.g. trouble with visual discrimination tasks) -Physiology (e.g. neurons only respond to stimuli they have been reared with) -Morphology (e.g. neurons make fewer and aberrant interconnections with other neurons) -For experience expectant if the expected information is not received then there leads to alterations in all aspects of development -In behavior, physiology, and morphology -I already gave you the example of expecting visual information but if for whatever reason the newborn can not process visual information then there are immediate changes to the physiology of the neurons because they are in contrast to a newborn who can see whose neurons are kind of going crazy with all the new visual information like lights and things like that - a newborn who can not see will not have these same neurons firing -And so coming back to LTP - this idea of use it or lose it - if you don't use neurons in a particular way than eventually the neurons stop firing to that information because in the case of visual information there is nothing for the neurons to respond to and so those neurons don't generate more and more synapses -There is also a difference in not just their activity but in there morphology - so neurons in the visual system that are not used make fewer connections with other neurons -They may instead have greater connections with inter-connections in the auditory cortex -As I mentioned if someone is born without the ability to see then maybe they will have a better sense of touch or better hearing - so that's the behavior component -And related to behavior are the neuronal resources that support that behavior - so if you are relying more on auditory cortex than that would be represented in the morphology of the neurons

Development of Axons and Dendrites

-If neuron doesn't die, it develops axons and dendrites -Purpose is to communicate with other neurons -Once the neurons get to their destination and they don't die or some weird thing doesn't happen then they can start to focus on building the neuron -The neuron at this stage is simply a neuronal cell body but once they get to their destination they start to develop axons and dendrites -Axons and dendrites are for signals, communication - the action potential travels down the axon and then when it meets another neuron and has to tell it something it communicates through neurotransmitters -The axon and dendrites are how neurons transmit information - they need them in order to communicate to each other

Development as a Dynamic System

-Linda Smith and Esther Thelen -How do we explain that brain development occurs? -Development is an emergent product of many decentralized and local interactions that occur in a specific time -Development is self-organizing -Systems generate novelty through their own activity -When esther thelen and linda smith presented this idea that development is a dynamic system it was kind of revolutionary -And by dynamic system they are referring to the idea that the brain and development is not static - that it is the case that when something is dynamic it is constantly changing -That it changes and adapts in response to new information -In other words it updates current representations -One example might be when a baby sees a german shephard for the first time and the parent says thats a dog - they go around thinking that's what a dog looks like and then the next week they see a chihahua and the parent says that is a dog - that can be pretty confusing for a baby - because chihahuas and german shephards look quite diffferent - they are different sizes but there are certain elements that are the same between those and so eventually it updates that information to have a schema of what a dog looks like -That's a dynamic system - that's dynamic understanding of information about the world -And they used it to explain that brain development occurs - because its pretty philisophical that we know that our brain changes -How do we know? We don't see it change - we see the effects of our changes from our behavior and our cognition but knowing that brain development occurs is only through the effects on behavior -When you read it you will see that they say this complicated sounding phrase so I want to untap what that means - they say development is an emergent product of many decentralized and local interactions that occur in a specific time -What they are saying - lets start first with local interactions - when they refer to local interactions this refers to different regions of the brain so you have the prefrontal cortex you have the amygdala you have the hippocampus - each of those are local regions - local regions that are decentralized which means there is no one center of the brain - there is no hub - there is no control part of the brain - the prefrontal cortex can help you have cognitive control but it doesn't mean that its in charge -So all of these regions kind of develop independently early in life -But development happens because all of these regions start to have connections with one another and those connections help the brain be the emergent product - to be one cohesive organ that works in the service of helping you interact with the world -So early on the connections between the amygdala (emotion processing) and the prefrontal cortex are decentralized - they are not really talking to each other and that is why a child has a harder time controlling the emotions that are processed in the amygdala because it doesn't have a good connection with the prefrontal cortex which helps it control or dampen the emotional response -But the emergent product happens when those two regions start to communicate with each other and then the prefrontal cortex can help control the emotion processing - the emotion regulation -This last part - that occurs in a specific time - is referring to the fact that most of this development of this type of development - of local regions starting to talk to other regions - happens in childhood and adolescence - it doesn't happen when we are over 40 or something - that is not the time of getting better emotion regulation - that happens earlier in life -And then the last part is that development is about organizing - and that's just a fancy way of saying that things happen through trial and error -That especially before we are verbal - before we have language skills - the only way we learn about the environment is through trial and error - its not possible for someone to sit a baby down and say now this is how you learn to crawl - we don't do that - babies learn to crawl because they self organize - they play around with moving their limbs and eventually that moves them along and they learn that they can crawl -Here is a baby - he is about to be self organizing - because as they define it development is finding a solution to a problem that works within your constraints - the problem this kid has is that he wants that toy and his constraints are that he doesn't have any physical agility - he isnt that coordinated yet and so crawling is a perfect example of trial and error learning -No one told him to move one arm and then the next arm - he is going to wobble and fall - and then he gets reinforced because his mom is like that's awesome you just got that toy on your own and that social component is also really important for trial and error learning that we will talk about with language development -There is no preset hard-wired program for crawling in the brain -Instead, crawling is a self-organizing solution to a problem -But anyways you can see this is what esther thelen meant by self organizing that its trial and error - that the development happens and the child is developing because they self organize -Emergence: coming into existence in a new form through ongoing processes.

Postnatal stress

-Maternal (Parental) Care -Abuse or Neglect -Maternal Separation -The way postnatal stress is studied in animals is mostly done in seeing how much variation there is in maternal care because having either abusive rat mom is as negative as it is in humans that is neglectful or abusive -And equally stressful for animals is when you separate them from their moms -The same is true for humans in terms of policy perspective there is a big debate on whether or not you should keep kids with their parents regardless of the situation or remove them from their home because it can be very stressful - so stressful in fact that it might match the level of abuse that they are experiencing

What does daily stress do to adolescent cognition?

-Middle and late adolescence reported their daily stress during a two-week study -They visited the lab to perform cognitive tasks on a high-stress and a low-stress visit -So one study we did in our lab was to study adolescence and their daily stressors -So not kids who have chronic stress but just day to day what stressors you have and they were texted throughout the day for 2 weeks at a time and we asked them to come to the lab once when they had a very stressful day and once when they had no stress on that day -And we asked them to perform some cognitive tests and the reason for that is we are simply measuring whether the brain responds differently whether or not you are feeling stressed when you are an adolescent and one thing we found is that teenagers take more risks when they are stressed and the reason parents care about that is because teenagers are already more likely to take risks and so if you add in to the mix feelings of stress then that might amplify that -Teens made riskier choices on high-stress vs low-stress days -But also what we found is that teenagers are worse at reuglating their behavior -On low stress days there are no differences between adolescence and adults in how much activation they have in the PFC during the self regulation and self control path but on the high stress days the adults are ramping up the PFC whereas the teenagers are kind of ramping it down and so that could be because the PFC is just simply not as developed and so it has a harder time recruiting these resources when they need it most and it also suggests that stress has an effect on the frontal cortex of the brain in adolescence and not so much in adults and this comes back to the life cycle model of stress that different brain regions are more susceptible to stress at different points in your life -Teens engage the PFC less on high-stress days during a self-regulation task -So in childhood it's the amygdala and hippocampus -In adolescence it seems to be the PFC -Under high stress, teens who took more risks had less PFC activation -Heres just another example of that -In this research we measured the amount of risks they were taking and found that the teenagers who took more risks in the lab were showing less activation of the PFC -So again the PFC was not as helpful during times of stress in the teenage group

How does A-not-B relate to Dynamic Systems Theory?

-Multicausality—multiple causes for error. -Knowledge about correct location is emergent: -It emerges from multiple components of the task and previous history of the infant (e.g. what happened right before) -Infants self-organize based on what information is available to them and their ability to hold that information online

Myelination

-Myelin is a fatty protein that wraps itself around an axon as a form of insulation -Increases communication speed between neurons -In order to make the speed of transmission faster the axons have these fatty acids wrapped around them and they help to speed up the transmission -A lot of myelination happens well beyond prenatal development - in fact myelination is one of the last bits of brain development that continues into the 20's -That as we get better able to communicate you need good communication between prefrontal cortex and amygdala to control emotional responses a lot of this starts to increase and improve during adolescence because myelination facilitates that -All of this we have looked at so far is still happening just in the first trimester so it's a really critical time in development

Are the plastic processes that operate during development the same as those that operate in adulthood?

-NO! -Local environment is vastly different -Wiring vs Rewiring the Brain -So to answer this question: it may be the same mechanism you still have synaptogenesis in particular areas of the brain you might still have neurogenesis but the local environment is vastly different -If you learn something as an adult vs. learning something as a child its going to be represented differently in the brain simply because one obviously had more experience then the other -This is kind of the difference between wiring the brain early in development vs. rewiring the brain as an adult

Experience-Dependent Processes

-Neural plasticity based on changing environment -Why? -A species cannot count on certain important experiences to occur at particular points in the lifespan -Experience unique to individual's own environment -How can we learn about these processes? -Change the rearing environment -So how do we study experience dependent processes -Again this is plasticity based on a changing environment and one way to study this is to change the rearing environment -So most of us have visual input we get early in life but not all of us are reared in the same way - so to study this experience dependent mechanisms people have turned to animal models where they vary how complex their environments are

Environmental input can change phenotype

-Neural tube defects associated with deficiency of folic acid -In 1992, the U.S. Public Health Service recommended that women of childbearing age increase consumption of the vitamin folic acid to reduce spina bifida and anencephalus. -In 1996, the U.S. F.D.A. authorized that all enriched cereal grain products be fortified with folic acid -When women are preparing to get pregnant or want to get pregnant or during the child bearing age there is often a recommendation that they start taking folic acid supplements -Because folic acid has been found to reduce the incidence of spinabifida -Here are the data on how spinabifida was produced -And here is an example of how the environment can change a phenotype -We often think about prenatal development as all happening inside -The environment doesn't affect it but the case of spinabifida and folic acid exemplifies how that is not true -The defects are associated with deficiency of folic acid -Here are the trends in spinabifida - here is 1992 when US put this public service announcement out and you can see immediately the stark decrease in spina bifida trends -And now it is pretty rare for someone to be born with spina bifida because of all the knowledge we have of folic acid and the fact that it is a direct cause of spina bifida

Proliferation

-Neurogenesis: birth of new neurons -100,000+ per minute! -Occurs by process of cell division -First lets start with the question of how does a brain get populated -After the neurolation the next major step is called proliferation -Proliferation is referring to the growth of new neurons which is neurogenesis -There are at this stage in life about 100,000 new neurons born per minute -And it occurs by the same process you saw when the two cell organism became the four cell and then eventually the blastocyst -Its simply that the cells just divide -So heres what happens -If you have one cell it becomes two cells but imagine what would happen if each of those cells then went on to divide -If this cell divided, and then this cell also divided what would happen to the brain? -It would have too many cells - we wouldn't be able to keep up within this small space -We wouldn't be able to keep up with the number of cells that were in there -And so instead what happens is that for each cell that is dividing there is only one daughter cell that keeps dividing -So this cell - these are both daughter cells - and only one daughter cell goes on to divide -So one of them stops dividing and the neurons that stop dividing start to migrate to their final destination -They migrate to wherever - the cerebellum etc - wherever they are going to go they start migrating -The other cell meanwhile continues to divide and then gives rise to two more cells and then you can see the pattern - same thing happens on and on until you completely populate the brain and different regions of the brain

How does neuroplasticity occur?

-Neurogenesis: the birth of new neurons -Synaptogenesis: the birth of new synapses -Plasticity occurs through two main mechanisms -Neurons are the nerve cells of the brain and in general humans do not have neurogenesis after they are born -Again the only two places this happens is in the hippocampus and olfactory and that is in response to our need especially in the hippocampus to incorporate new learning (memories) -Synaptogenesis happens throughout our lifespan all the time - it also involves the birth of new synapses but also the pruning away or elimination of synapses -We also have in the hippocampus the pruning away of neurons because you cant have an exponential growth of new neurons in the hippocampus and so some neurons die -In general the main distinction is that neurogenesis happens before birth except the hippocampus and synaptogenesis happens in response to learning -So plasticity in adulthood is really the synaptogenesis - that's what plasticity refers to in humans

Neuronal Migration (6-24 prenatal weeks)

-Neurons are born in a different place from where they end up -Active Method:Neurons move in an inside-out direction to form six cortical layers -So then what happens after that is after they divide the cells all start to migrate - some earlier than others -And again its implied this happens because the neurons are born in a different place from where they will end up -They have to born somewhere and have to end up somewhere else -And so there is something called the active method and that means that the neurons move in an inside out direction -If all the neurons are born at the base - the new neurons - the migrating neurons move past the ones that were previously generated -E 8.5 refers to embryonic day 8.5 and embryonic day 10 and so on -This is just to illustrate that early on you only have one layer of a cortex but eventually as the neurons start to populate the rest of the cortex you eventually end up with the 6 layered cortex and that's true of all primates that we have very complex type of cortex that has different types of cells in each of these layers -Its remarkable that we have these rows of cells and how they know which row they are supposed to end up in is pretty cool

Phases 1 and 2

-Occur prenatally (Phase1: 2 months gestation; Phase 2: 3-4 months gestation) -Dominated by genetic mechanisms -Experience-Independent -Process can be influenced by genetic mutations, infections, toxins -Cannot (easily) be influenced by experience from the external world

Phase 3

-Occurs right before birth, during birth and early postnatal months (8 months gestation-1 year postnatally) -Experience-expectant and experience-dependent mechanisms -Experience-Expectant -Input from the external world are necessary for proper final adjustment -Experience-Dependent -Organization of synaptic contacts related to the experience of each individual -The one that is most diverse in that you start out with a low number of synapse that increases substantially during the course of this phase because the major event that happens gestationally is birth and that happens right in the middle of phase 3

Forebrain, midbrain, hindbrain

-Once the neural tube is closed we have three vesicles that form -The forebrain, midbrain, and hindbrain -And the longitudinal dimensions of the neural tube are what eventually give rise to major subdivisions of the brain -So the forebrain becomes the cortex, the prefrontal end is the whole surface of the brain and the midbrain becomes the regions we have already talked a little about amygdala, thalamus -All the regions that are underneath the cortex -And the hindbrain becomes the cerebellum and the spinal cord -And so again how does this happen? How is it the case that something relatively small starts to generate enough neurons to populate something so big as a cortex -And relatedly how do the neurons know that they are going to become a cortex cell versus an individual cell or something like that -All of those decisions are happening through genetic signaling - neuronal signaling

Monocular Deprivation

-One eye is sutured shut during the sensitive period -Deprived eye becomes functionally disconnected from visual cortex neurons -"Use it or lose it" -Open eye becomes more functionally integrated with both sides of visual cortex -The most famous experiments to test this are the monocular deprivation experiments -They sutured an eye shut of a cat and they found that (the reason they started with a visual system is that a cats visual system is very similar to humans but also because we have two it was a built in experiment, a built in control they only sutured one what would happen to the visual cortex neurons of that one eye) -And what they found is that those neurons that were associated with the shut eye became functionally disconnected from the rest of the brain -That is even within a few weeks those neurons stopped functioning because there was nothing to function - they werent seeing anything whereas the open eye those neurons became stronger and more vigurously fired in response to visual infromation because you can think of that open eye as doing double the work - now one eye is taking in all the visual information and the load is not distributed between two eyes

Multicausality

-Organisms are complex systems composed of many individual elements -No executive agent: No single element has causal priority (hence: Multicausality) -We have come back to the brain example and different brain regions - you can make the analogy that the individual elements are the individual brain regions that come together -That over development start to work together more efficiently -Its important to remember that there are no executive agents - that means that there is no single element that has causal priority -There is no one brain region that is the most important - they are all important and that goes back to the fact that we dont just use 10% of our brain because all parts of our brain are contributing to some aspect of our existence at any one time -Self-organization: Developmental change occurs because of relationships between organic components of the system -Development is a series of evolving and dissolving patterns of stability (changing) - rather than an "inevitable march" towards maturity -... (we are not just marching towards maturity because for one there is no definition of what maturity is - its not an on and off switch you arent just suddenly mature - there are a lot of things that happen for you to exhibit mature behavior but its not just one element - but more importantly is that development doesn't just mean that once you learn a skill that's the only way you do something - if you think back to crawling - why don't we all crawl around when we get around campus? Instead we walk. Why do we walk? -We learned how to crawl and it was so hard and took so long why do we walk now? Its way more efficient to walk and as our bodies become more stable we feel more comfortable being upright - it would be weird if I started crawling because that's not how our species interacts but also its not as efficient because we are using more energy but then we also don't have access to our very useful tools which are our hands -Crawling and walking is a perfect example for this statement - because lets replace development here with crawling - crawling evolves and then it dissolves within about 6 months -We spent a lot of energy learning to crawl but we only use it for about 6 months -Doesn't mean we forget how to crawl but we don't rely on it anymore - we replace it and so this is referring to that replacement that we do -Early in life language is also an example - we speak in very short sentences - because we don't have the tools and as our language repitoire grows we replace the standard basic units of language with more sophisticated language that allows us to have better interaction with others -And so if we had an inevitable march for maturity it would mean that once we learn something that would be the ultimate thing to learn - that once we learned to crawl that was the best we could do - if we had no ability to stop doing something or remove the preferred mode of mobility at that point then we would always have too much information - do I crawl? Do I walk? - we wouldn't get rid of things we didn't need anymore -Its basically saying we are able to prune away and get rid of things that arent serving us even if at some point in development it served us very well and it was necessary -And btw it also explains why we don't just start walking - development happens within our constraints - we are physically constrained early in life our legs cant hold up our bodies - we are disproportionate in particular ways and so it would just be too hard to start to walk just right off the bat

Outside-in Migration

-Passive : neurons are displaced by new neurons -Thalamus (Rakic, 1977), hypothalamus (Ifft, 1972), spinal cord (Nornes & Das, 1974), hippocampus (Nowakowski & Rakic, 1981) -Other parts of the brain - not in the cortex so the subcortical region have whats called outside-in migration -It's the exact opposite so now the passive neurons are displaced by new neurons -In other words the new neurons don't move their way past the older guys but the older guys are just kind of pushed out - they are physically pushed out -And this happens in the thalamus, the hypothalamus, the spinal cord, and the hippocampus -So here I want you to follow the blue cells and you will see that the blue cells don't stay at the bottom in fact they are pushed up by the newer cells that are coming in -The yellow ones in this case are the newer ones

Phase 3 across evolution

-Phase 3 differs across evolution across species -Earlier I mentioned that rodents cant see when they are born and in part that's because look when their synaptogenesis gets ramped up - its after birth -They have the system where their brain isnt necessarily having this experience expectant mechanism its not proactive instead its reactive to the fact that they get visual experience - visual input -And so then they start ramping up -In humans you can see its a much longer period of change and what this does - this protractive phase of development - is it increases the volume of the visual cortex in the primate brain we have a much bigger representation of the brain devoted to visual processing than a rodent for instance because we are visual creatures we rely on that sense very much more so than rodents who rely more so on olfaction - their olfactory is huge relative to the rest of their brain and ours is small compared to the rest of our brain

What is stress?

-Physiological, biological, and emotional reactions to particular events -It's the body's way of rising to a challenge -Its the bodys way of knowing there is threat in the environment -That is a good thing - its a good thing for us to know when we might be chased by a lion for instance

An example of multi causality: object permanence

-Piaget: 'when do infants acquire the concept of object permanence?' -Object Permanence: the understanding that objects continue to exist even when they cannot be seen, heard, or touched. -One example of multicausality which is called object permanence -Object permanence is this - you see this cup and if it goes here is it still here? Yes of course because you have object permeneance - you know that this object continues to exist even when its not right in front of you -This is an important concept because before that when a baby mom leaves the room it is incredibly distressing because in their head they are gone -They are no longer available because they don't understand that the mom is in the next room and coming back - because they don't have object permanence -Once the child begins to have object permanence they have a mental representation of people or things that are not immediately in front of them -And so piaget spoke a lot about how important object permanence is for development because if you don't have a mental representation of something that is not in the room - you are going to be way too stuck on only the things in front of you and you are going to be incredibly distressed when you are not in front of something you want like a toy or something like that -Its also the reason babies are so good at playing peek a boo with -A-not-B task a task to test object permanence -Multicausality to explain A-not-B error -There was a famous task the A not B task that was created to test object permanence -The reason we are bringing it up here is because it is also a good way to explain to you the multicausality that explains the A not B error -The A not B task - this is a baby who is about 10 months - there are two wells (two little holes) here and here - they each have a little cloth on top of them -The experimenter sits here and says to the baby im going to put the ball in this well and the baby sees that and then they cover it up with the cloth and say where is it? The baby goes into here because he saw that the ball went into that well (well A) - they do like 10 trials - and then they say to the baby ok here is the ball again - now im going to put it over here -We are going to cover it up and then they ask the baby to point to where the ball is - what does the baby do? He goes to well A again even though he saw it go into well B -This is called the A not B error -There are multiple reasons for the error - habit (if you just trained a baby 10 times on this its like when you move to a new house you are driving a long and before you know it you've missed the turn because you kept thinking of going to your old house - it's a habitual thing), the delay (the working memory - babies have poor working memory at this age so that means that its just simply too taxing - if you wait 5 seconds in between the baby cant keep in mind where you put it the new time - they rely on habit of where it went) and there are other reasons why the A not B error happens -8-10 month old infants consistently make the error -Infants older than 12 months of age perform this task correctly (reach for B location) -Why this significant shift in correct performance at this age? -Multiple causes for improved performance -Older then 12 months and kids start to perform the task correctly - that is they go to well B -So why is this huge shift in ability between these two months of age - what happens between these two months of age that lead to improved performance? -Well there are multiple reasons for improved performance

Experience-dependent neuroplasticity

-Production of new synapses through activity-dependent mechanisms (LTP) -This experience dependent neuroplasticity happens to the produciton of new synapses -The experience expectant changes are typically referring to the pruning away - because experience expectant means you overproduced and then you are pruning away -Whereas experience dependent is a new piece of information its new learning, new memory, a new experience so you don't have neurons and synapses for those new experiences so you generate them through LTP -And so you have this activity going on here at the synapse where this presynaptic neuron is releasing neurotransmitter to this postsynaptic neuron and if that happens a lot overtime eventually this new synapse will form and so this kind of explains why even though across development we have this general overproduction strengthening elimination you can have periods in development where you overproduce again -That you generate new synapses -Its not the case that you are only just pruning away -So coming back to the example of you guys across the 4 years of college - remember how I said at graduation you will have fewer friends and they are very strong -But what happens if in your 4th year you joined a new club - it doesn't mean that you are unable to establish new connections it simply means you have to now create new synapses to represent those new connections -And so this is what allows us and allows us to adapt to new circumstances -If it was the case that our brains were so rigid that we only pruned away once we hit puberty we would never be able to learn new things we wouldn't be able to incorporate new information or social relationships or whatever it was

Summary of visual deprivation experiments

-Prove that the organism expects visual input -If one eye does not receive expected input by a certain age (developmental stage), the other eye (and related neural processes) compensates -These experiments prove that the organism expects visual input (these experiments were done in freshly newborn kittens so immediately if the visual information wasn't provided then the eyes started to adapt so the other eye compensates) -Expected experience participates in the organization of a detailed neural pattern -typical pattern of experience --> typical neural organization -atypical pattern of experience --> atypical neural organization -reason: nerve cells of visual deprived animals make fewer connections and altered patterns -Its very simple if you have a typical pattern of experience (experiences visual input) you have typical neural organization but if you have atypical pattern of experience where you don't get visual input right away then immediately your neurons start to adapt to that circumstance and they start making fewer connections and morphology is different

How do neurons know where to go?

-Radial Glial cells provide guidance -Glia are supporting (helper) cells -So how do the neurons know where to go? And the answer to that is there are two main answers that happen -One is that glia (the supporting cells - neurons use them to move their way along - they physically use them as a bannister to move along - upon which they can migrate) and so in that sense the glia cells kind of serve like a skeleton they serve like a ladder for the neurons to move on to where they are supposed to go -So that's the physical assistance that the neurons are getting -The second is that the neurons are getting molecular signals - that interestingly don't just tell them where to go but also tell them where to stop -molecular signals provide "stopping" signal -This image is a representation of a hippocampal area - this is a normal developing hippocampus where the molecular cells are doing their job and you can see clear layers of where there are a strip of neurons here that are distinct from the ones above it -In this case this is abnormal because the neurons kind of got to the same area but didn't get to exactly the right spot so you can see its just a blurryier line between the different divisions of the hippocampus -and so how we know this, is people who have studied these molecular signals - will knock out some of the molecular signals and will realize that without the signals the neurons cant get to their destinations as well as they should

Maternal seperation influences offspring behavior

-Repeated maternal separation in infant monkeys increases anxiety -In monkeys they induce stress by also doing the seperation experiments and what they find is that the maternally seperated monkeys in black vs. the control monkeys in white here have a higher startle response -That simply means they are just more anxious then the ones that are not seperated from the mom -So those data are from animals and I mentioned its challenging to do them on humans because we cant ethically move kids from their parents just to see the stress response but there are natural experiments in humans where for whatever reason the child is removed from the parent or they are raised in a suboptimal caregiving environment and some of the most informative data on this come from a study done in romania where because of some political circumstances of the country a lot of children are moved to orphanage care and that orphanage care was suboptimal so nelson at harvard has studied these kids for many years and found that the brain regions or behaviors associated with the brain regions of the hippocampus and the amygdala are the ones most affected in the kids that receive suboptimal care

First Trimester (Fetal Period)

-Sex hormones direct male and female brains along slightly different paths -Amygdala, hippocampus and hypothalamus in particular -Differentiation of sex organs, guided by genetic information -Both male and female embryos go through a bisexual stage, during which no sex-linked characteristics can be discerned. -Both have a surfaces mass that becomes testes in males and eventually deteriorates in females -In males, sperm ducts develop and female ducts dissolve -In females, the fallopian tubes, uterus and vagina develop -During the fetal period - now we are passed the embryonic period - we have differentiation of sex organs and differentation of male and female embryos -I want to make a distinction because chromosomes decide whether or not you are XX and XY but during the fetal period is when there is further differentiation of regions of the brain that are going to be distinct -So for instance - there is some data to suggest that the male amygdala and the female amygdala are different and that all happens during this period of development -So that's what we mean by differentiation of brain regions that differ by sex happen here -But also there is differentiation of sex organs

Third Trimester

-Significant maturation of the nervous system -Sensitive to musical sounds, changes in speech sounds, stories -In the third trimester there is a lot of sensitivity to external information like musical sounds, changes in speech sounds or stories -And so often moms are told they should interact with their babies by talking to them - it helps the baby bond with their mom even before they are born because they start to recognize her voice -And researchers who study language development talk about this - use this knowledge to say that its not like we are ever born completely adnostic to language because we start to hear our native language in utero once we have ears that can hear the world around us - so there is a big debate about whether language is innate or language is learned and its hard to disentangle that question because new born babies have already been kind of biased by the language in which they are reared

Songbirds and neurogenesis

-So how do we know that neurogenesis happens? -How do we know its tied to particular behaviors? -In humans its hard to study new neurons because you have to label the new neurons with a special dye so its hard to know how it relates to new neurons we incorporate but we have learned a lot about the relationship between learning something new and generating new neurons from animal models -Researcher discovered this by studying songbirds -Songbirds are seasonal song learners which means that every spring they learn a new song in order to attract mates -This is interesting because they completely forget the song from last season every year and so researcher wondered how is they can represent this new song - that's a lot of learning for a bird to do every single year -Songbirds generate new neurons seasonally in the "song learning" area -He found that first there is a part of the bird brain called the HVC - and all you need to know about the HVC is that that is the part of the brain that represents new songs -And what he found is that in song season - the spring - the HVC gets much bigger in songbirds and then in the winter and summer once they don't use new songs the HVC shrinks again and so this literal expansion and shrinking of the HVC are the new neurons that are created every spring time for the birds -On the X axis is different seasons - the Y axis is showing you the density of neurons -BrdU is how you label a new neuron - so if you want to know if there are new neurons in a particular tissue - then they inject BrdU and they used to count how many BrdU labeled neurons are there -So this is the density of BrdU labeled neurons and what you can see is in october (winter) there are very few new neurons in the HVC of the bird in January they rapidly shoot up -They are just starting to learn the new song - they are getting prepared because by the time they reach spring time they want to be experts at that new song because that new song is going to attract mates -Researcher said theres this seasonal rhythm in new neurons and this is revolutionary because at the time it was thought that neurogenesis did not happen in the adult brain and he is showing that not only does it happen in the adult brain but it happens on a seasonal basis - that our brains can decide when to have new neurons and when to not have new neurons -And that decision comes because it is tied to a very important behavior that is tied to reproduction and survival and things like that -And so neurogenesis occurs in the brain sometimes in ways that are dependent on behavior - always actually in ways that are dependent on behavior

Overproduction of synapses leads to pruning (elimination) around puberty

-So there are 5 distinct waves of synaptogenesis that are highly orchestrated -Waves 4 and 5 are less so because they are more experience dependent -This is a lot of years of research in which they focused in on synaptogenesis in the visual cortex -Again the visual cortex is easy to study because you can study it in animals pretty easily and it's a pretty consistent process that happens in all of us -You are looking at the density of synapses on the Y axis - this line here represents conception - this represents birth and the last one here is death -And so youll notice that there are times when you have more synapses and times when you have less synapses and that's all tied to experience -In general the overproduction happens here in the middle eventually leads to pruning around puberty - overproduction then you have pruning -If you look at synaptogenisis in other brain regions it's a very similar pattern - overproduction and then pruning so lets start at the begininning we have the density of synapses - then these 5 distinct waves (phase 1 through 5) -Notice that the first one is experienced independent - because its prebirth we all go through very similar 9 months of gestational development and remember the experience in this case is visual experience so you are not having any visual experience while you are in utero and so you actually do not have many synapses in the visual cortex in phase 1 and 2 because you don't need them -Your brain is busy working on migration and cell division and all the other things it needs to set up before it can focus in on the visual development -And so these first two phases are under genetic control mostly in that the brain is not focused in on the visual cortex at this stage -But then in phase 3 youll see this first boost of overproduction of synapses - there is a sharp increase - the slope is really steep that happens right before birth and then right after birth -And this is an experience expectant and dependent mechanism -But the important thing is the brain is getting ready for visual input it will receive at birth - so because our gestational development is so well timed and regulated - 9 months - our brain knows when it should start making more synapses in the visual cortex because if it waits to build up the visual cortex until birth the animal or human will already be behind in being able to process information when its born -And so that's why when we are born unlike other animals like rats or mice who cant really see when its born we can see right away not as well as we can later in life but certainly we can make out faces, we can identify the mother through smell and other things too but there is a ramping up -And this is an example of experience expectant mechanisms because the neurons are expecting for visual input to happen at birth right in the middle of phase 3 -Why does it keep increasing after birth? -Because of our experiences and thats what makes it experience dependent - that now all of our moms look different so now you are starting to get specific about the visual information that you need to know -So that's its still expectant in that its still ramping up in everyone but the particular visual input you are receiving is dependent -So you have this overproduction and then during this time connections between neurons are relatively weak and the reason for that is because the brain wants to have all the neural resources you need and all the connections you are going to need but it doesn't want to hang its hat too much on those connections because it is unknown at this point the connections youll need to strengthen so they are relatively weak -During phase 4 - so this encompasses all of childhood - youll see the visual cortex synaptogenesis plateaus and during this time is when the connections between the neurons become very strong -That's because through LTP you are strengthening the visual input that is specific to you and you are becoming better and better at processing visual information because your synapses are getting strengthened -But now we move onto pruning and this happens around the time of puberty - at puberty there is a lot of hormonal change so it makes a lot of sense to speculate that hormones induce this pruning process that now that you have reached sexual maturation your brain is going to start redirecting and have new tasks and skills it needs to focus on -And so pruning happens around the time of puberty -Researcher describes this as an experience dependent mechanism but that is up for debate - its dependent in that puberty happens at different times for people - great variability especially for males and females - but its expectant in the sense that it happens to everyone - everyone undergoes puberty at some point -Some delayed some early but everyone undergoes it and so the jury is kind of out on whether this pruning is expectant or dependent -But I say its similar to the one in the stage before that its really both - the fact that it happens is expectant but the timing is dependent -And then eventually the connections between the neurons or synapses you don't need become weak and die off so you don't need them

Individual Traits

-Sociability, inhibition and neuroticism have strong genetic components -This also interacts with environment -I.e. a parent who is temperamentally sociable is more likely to have a sociable child, which may be due to genetics and/or by modeling the parents social behavior Healthy teeth -You understand that individual variation in genes causes individual variation in traits -There have been a lot of psychological studies showing that some particular traits like how social you are or how inhibited you are, or how neurotic you are have strong genetic components -And in those studies people have typically taken a group of people from a family and looked at how variable these traits of interest are -But this too interacts with the environment and one classic example is that its hard to disentangle the contributions to the offspring -So for instance if you have a parent who is very social and likes to interact with people they are more likely to have a child who is also very social and interested in social relationships - however it is unclear if that child is social because the parents passed on some genetic components of them being social or is it the case that the child is modeling the parents behavior -One way that people tried to study this was to see how stable these kinds of traits are - and by stable I mean if someone is socially inhibited - the opposite of being very social - is that something that is consistent across development? -Are you who you are from when you are born or did the environment you are in play a bigger role in shaping who you are -If you are born as someone who is pretty shy and they test you when you are 4 or 5 does that mean you will be a very shy person when you are 20 or 30? -Perhaps the most famous experiment that tried to get at this came from Harvard - he has tested people since they were infants - so before they were verbal and followed them about their lives to ask this question - that is it the case that you can change some of these genetically informed personality traits -Child is put in a new situation - commonly used as a way to measure how distressing people find novel situations to be - you cant see the experimenter in this shot but the experimenter is someone the baby has never met before so they are measuring how this child responds to this novel social situation -Researcher built his career on this idea that these traits are very stable - that maybe whatever genetics contributed to his behavioral inhibition are apparent throughout his childhood -and maybe he is even able to come to a lab because his parents have scaffolded him and helped him get through being shy and behaviorally inhibited because it could be the case that he went on to develop social anxiety and he couldn't even make it to the experimenter because he was so nervous -but he is not that bad he is not so nervous but he certainly has traits that seem to have persisted across his development -The other way that these interact is that we illicit certain things from the environment by our own predispositions -So it could be the case that that boy was seen by a parent or caregiver as fussy so they don't want to interact - and so overtime they maybe picked up less or are given less opportunity to experience new friends or other adults that would help mitigate his distress so that's another way that our own personality traits that may be genetically informed interact with each other -We illicit certain reactions from the environment -One common way people talk about that is that attractive people illicit a particular type of reaction from the environment -Even from a very young age - we might think its superficial but attractive people have a different experience with the environment then people who are less attractive - these people are pretty attractive and they probably had a different experience than people who are less attractive - whether or not they are behaviorally inhibited or not they may get more attention from their world

Abnormal Development

-Spontaneous abortion (15-20% of pregnancies) -Birth Defects -Genetic Disorders: linked to specific genes (e.g. Albinism, sickle cell anemia, color blindness, hemophelia) -Chromosomal Disorders (e.g. Down syndrome, Turner's syndrome -Genetic variability may contribute to abnormal or atypical development -The first is that about 20% of pregnancies end in spontaneous abortion - that means that the mom may not realize she is pregnant because some genetic abnormality leads to the miscarriage -Other ways are birth defects or chromosomal disorders such as down syndrome or turner's syndrome also are related to variability in genetic or chromosomal development -So you probably know that down syndrome has an extra copy on the 21st chromosome and that one extra copy leads to development that is pretty far from a typically developing child who does not have down syndrome -Same with turner's syndrome - it's the case that individuals with turner syndrome lack one X in female so they only have one X -In Klinefelter syndrome these individuals have an extra X in males so they have XXY -And in those cases the parents determine whether this child will be reared as a male or female -And again this comes from variability in genetic information

Adverse Environments and Plasticity: The effects of stress on brain development

-Stress is a model or example of plasticity is interesting because stress is one of those circumstances that can be both chronic (that is you experience the same type of stress throughout your life or throughout a period of your life) or its acute (like having an exam coming up) and both of those types of stressors induce certain physiological and biological changes like you release cortisol in both of those circumstances but the difference is that if you have chronic stress throughout your life and if you have chronic stress when you are growing up and when you are very little and when you are undergoing developmental plasticity than that stress gets under your skin -That the stress itself and the physiology that accompanies stress becomes a part of how your brain gets set up and in some cases it can be maladaptive because it means that your brain has all the negative consequences of the stress response

How does eternal stress "get into" the developing fetus?

-Stress to mom increases glucocorticoid secretion, which then pass through the placenta -Glucocorticoids have significant effects on brain organization -glucorticoids are important for normal brain maturation -help strengthen axons and dendrites; help cells survive -glucorticoids can be harmful if prenatal levels are too high or too low -decreased numbers of necessary stress hormone receptors -delayed maturation of neurons and glia

Stress in the brain

-Stressors activate the hypothalamus-pituitary-adrenal (HPA) axis 1. Amygdala triggers stress response 2. Hypothalamus releases CRH and AVP 3. Pituitary releases ACTH 4. Adrenal gland releases GC's (cortisol in humans) 5. Once stressor has passed, feedback loops (hippocampus) are supposed to "turn off" the stress response -Stress becomes maladaptive when stress response does not diminish and there are too many stress hormones flooding the brain/body -And the reason for that is the stress activates the HPA axis -And that originates in the hypothalamus -And it first triggers the stress response through the amygdala - your amygdala is a threat sensor and so when there is threat in the environment whether it's a stick in the ground that looks like a snake its better to be safe than sorry so you are going to assume it's a snake first and then regulate and take a closer look and then youll decide its actually a stick and that you arent actually in harms way -But the amygdala is the first stress response -It then sends a message to the hypothalamus which releases CRH and AVP (stress hormones) -It then from the pituitary relases ACTH and all of these are simply stress hormones -And finally we release GC or cortisol in humans -Cortisol is the stress hormone that helps you mobilize and recognize the stress in the environment and this cascade happens every single time you have a stress response and the final step is that the GC's eventually send a message back to the brain to say that once the stressor has cleared or you are sure there is no stress in the environment this is the feedback loop that turns off the stress response - it works like a thermostat - like once you have a high enough response and there is no threat in the environment then the GC response or cortisol release should weign and eventually shut off -But allostatic load occurs when any one of these steps goes array - either you have too much release of any of the hormones during these different stages and/or the feedback loop fails to turn off the release of each of these hormones -Then you are left with the situation where you have too many stress hormones in the body even if there isnt a stressor and that's what leads to a failure to habituate -Your brain doesn't know how to tell the difference between a real threat and a perceived threat -This is the same response that occurs whether a lion is coming at you or you are in a social situation that makes you anxious - social situations can obviously be very stressful for people and individuals who suffer from social anxiety fail to turn off the response of the threatening situation

Stress is not always bad

-Stressors can serve to mobilize an organism -Stress is useful -'fight or flight' response -That's why we have a stress response because it mobilizes the organism -It is useful in telling you you are in harms way and the only way our bodies can be mobilized so quickly would be to release hormones that serve as an impetus to either run or have this fight or flight response -The problem is that even if we have an adaptive reason for having a stress response if that stress response is prolonged or repeated or doesn't get turned off when it should then that's when stress becomes maladaptive

Synapses

-Synapses permit the passage of an electrical or chemical signal from one neuron to another -Here is a presynaptic neuron which means that's the sender neuron -That is the neuron that has the information that will be transmitted to the postsynaptic neuron -The postsynaptic neuron is the receiver neuron and this is just one synapse bridging together two neurons -This happens all over the brain -An electrical synapse is represented here where information comes down an axon and then gets transmitted to the postsynaptic neuron -But the important thing is that this communication between two neurons - this creation of synapses can happen throughout life -In response to learning new information -So if the sender neuron does not already have a direct way to communicate with the synaptic neuron than synaptogenesis occurs -Synaptogenesis: the formation of new synapses between neurons -Long-term Potentiation (LTP): long-lasting increase in signal transmission between two neurons -LTP refers to long-term potentiation and that simply refers to the repeated signaling between two neurons -So for instance if the presynaptic neuron just sends one message ever to the postsynaptic neuron -A new synapse wont be created -But if you have LTP - the repeated stimulation from one particular neuron to another particular neuron LTP facilitates the signal transmission between the two neurons -It means there is an important communication between those two neurons and that is based on experience -that is based on the repeated stimulation of this communication -The way this relates to development is that there are particular times in development where synaptogenesis is more likely to occur

Heightened stress response in human adolescents

-Teens have larger stress response following a public speaking challenge than younger kids -So here is one example of that in humans -Gunnar has studied this question by asking kids to come to the lab - and asking them to give a public speaking lecture and they don't know ahead of time they are going to get this task -So first she has a group of 9,11,13, and 15 year olds - and the main point of this is that right before speech preparation everyone freaks out but as they are giving their speech the ones that have the highest stress response are those right in the middle of adolescence and this has been shown in many different ways -Whether it is perceived stress or actual stress adolescence have a more vigorous response -Some plausible explanations: -Interaction of stress hormones with pubertal hormones -Adaptive to be more responsive to the environment during this developmental period -Stress interacts with changing emotional systems during adolescence -Why might that be that adolescence have a bigger stress response? -The lymbic system is developing - the amygdala and all the regions that are supposed to be paying attention to the environment are on high alert as you transition into adolescence -The other possibility is that adolescence in post puberty is when those animals including humans leave the nest - and so now there are perhaps more threats in the enviornment that you should be aware of rather than your caregiver or mom or whoever -So now there is an evolutionary reason why the adolescent brain is more sensitive or paying attention to stressors and/or releasing more cortisol in order for you to pay attention to those new potential threats in the environment -Emotional systems are changing and you need to be more responsive to the environment

Brain plasticity and experience

-The brain is very susceptible to experience -That the experience we have in our everyday lives that we have from 10 to 20 years ago can still influence our psychological state, our mental wellbeing and how our neurons process information -That general term is called brain or neural plasticity

Experience-expectant processes differ from later developmental processes

-The degree to which they are age-dependent -Must occur early in life -And irreversible -Neurons become committed to a particular pattern of organization -Experience expectant process similar to earlier when we were talking about critical periods they are not critical periods but they are similar in that they are more age dependent -We expect them to happen by a certain age and they are relatively irreversible -What happens if you don't get visual information right when you are born? Then at some point it will be too late for you to build up that visual cortex because the neurons have expected it earlier in life

Studies in both animals and humans have shown that the brain is particularly sensitive to stress during both early childhood and old age

-The different brain regions are particularly sensitive to stress during early childhood and old age -And at different stages of development there are different brain regions that are more affected -So early in life - in early childhood it's the hippocampus that is most sensitive (amygdala also) in adolescence it's the frontal cortex -And so depending on when you experience the most stress that's the brain region that is going to be most affected -And subsequently the behaviors that are associated with those brain regions will be most affected -If you are having a chronically stressful life as a child it's the hippocampus that is going to be the most vulnerable and learning and facial memory are associated with the hippocampus and will be affected as well

Why is it adaptive for an organism to rely on expected input?

-The environment is already there -Take advantage of what should be there anyway -Genes sketch an outline and environment fills in the details -There are "eye" genes -There aren't "visual input" genes -Fine-tuning occurs by eliminating unnecessary synapses/strengthening necessary synapses -This happens because most of us have the same type of environmental information when we are born and so it takes advantage of that happening across our species -And because this happens for so many years across evolution we have genes that layout the foundation -The genes set out the unfolding of the visual cortex even before you are born -And then the environment fills in the details - so your visual cortex is pretty similar but then if you have very different types of visual experience then your brain will adapt to that -One example is that its related to vision but more related to us being social creatures is that we have a lot of experience with faces - that is a visual piece of information that we have become experts on - we all look pretty similar but we can still differentiate among people - we are very good at that -That happens because we are flooded with visual information in a face configuration but we all differ in the people we know and the people we interact with and so we become better able at identifying different features of the people we are most familiar with -Fine tuning or pruning happens by eliminating unnecessary synapses - so when you are born and you have an over abundance of neurons in language regions that is because the brain doesn't know which language you will need to know -So what starts to happen is that you start to become stronger in a particular language and you start to eliminate the unneccessary synapses you don't need because you are not learning 5 languages you are learning 1 and so you become really good at that one at the expense of being able to learn other ones

Experience-expectant information storage

-The organism is expecting some sort of experience -Sensory information -For example, the organism expects to receive visual information

Important periods of prenatal development

-There are important periods of prenatal development for different parts of the body -So for instance in this image here the dark bars denote highly sensitive periods for particular organs so youll notice here that the development of the heart is really important in the first few weeks of gestation -Doesn't mean that the development of the heart isnt important later on but because the heart develops so early on that teratogens that affect the heart are going to be more impactful early on rather than later on when the heart is more stable for instance -The eyes also in the first few weeks of gestation are developing rapidly and so they are more susceptible to teratogens earlier on then later on -Teratogens are any kind of toxin that may make its way past the blood/brain barrier and affect the fetus in a negative way -in the first two weeks as noted here is when you get the blastocyst and the inner cell mass and the neural tube forms -During that time the embryo is not susceptible to teratogens which is really fascinating - teratogens like smoking, drinking or things that we generally say we shouldn't be doing during pregnancy because it affects the developing baby those teratogens do not affect the blastocyst at all -In other words you are not harming it during that time -Its interesting because most women don't know in the first few weeks of pregnancy that they are pregnant - they don't find out till they miss a period but during that time all of this massive development and important developmental stages are happening and we arent even aware of it probably still going about their lives, drinking and smoking etc.

How does multicausality relate to brain development?

-There are multiple causes for acquisition of a new skill, for development -The article talks about multicausality a lot -And multicausality simply refers to the fact that there are multiple reasons that you develop -There are multiple reasons that you aquire a new skill -Crawling example is a perfect example of multicausal development because what went into that kid learning to crawl - motivation (they wanted toys), physical trial and error (they were testing out how you move arms and legs), reinforcement (parent saying that was great and that you should do that again), so there were multiple reasons any one of those things wouldn't have generated that product - just because kid wanted that toy doesn't mean it will spontaneously get up and crawl -Just because they move their arms and legs if they werent trying to move they wouldn't have moved -Maybe they would still learn to crawl if they got reinforcement from the parent - but the reinforcement helped propel that learning along -So in other words there are multiple causes for something happening -Multicausality - they are all working together - that's how development happens - if there is only one of them development wont happen - you need multiple reasons to be able to learn something - multiple things contribute to that learning

Inverted-U relationship between stress and performance

-There is an inverted relationship between stress and performance -And here by performance im referring to anything positively based -Like any kind of mental activity you have to do you need some amount of stress -If you didn't have any feelings of stress about the upcoming exam you maybe wouldn't study -With too little stress you are bored or don't mobilize (don't study) but if you have too much stress you feel anxiety (and might feel depression eventually) not just about an exam but about anything that might be stressful in your life and its this high stress that can be detrimental if its not regulated and decreased -theres an optimum amount of stress that can lead to high performance which is between too high stress and too low stress

Enrichment effects neuronal morphology

-These are old school drawings to show differences in dendritic growth -So here you can see that the non-enriched environment leads to fewer dendrites - and dendrites are used for communication so if you have less of them you are going to do less communication and eventually you are going to have slower processing speed and eventually you are going to have deficits of learning and all these other behavioral things that indeed they find

Why is this classification better?

-This classification considers: -The evolutionary origins of a process -Its adaptive value for the individual -The required timing for the process -The organism's active role in obtaining appropriate experience for itself -Why is this classification better than sensitive/critical periods? -One is that the classification considers the evolutionary origins of a process - meaning just that its optimal for member of the species to have visual ability then it makes sense that we don't all have to reinvent a brain region that processes visual information - all of us process visual information in the same place (the visual cortex) -Again its adaptive for the individual to have the same abilities and representations of abilities in the brain as other members of the species -It cuts down on the timing again if we all had to reinvent how to represent visual information it would take a long time - it would take a lot of gestational time for that to happen - instead the visual system gets developed pretty early on in gestational development because we have a system for it we have genes that help us get the neurons to the right place in the visual cortex - it's a pretty well oiled template for sensory information

First Trimester (Germinal Period)

-This diagram illustrates what we just saw in the video of how within the first 24 hours, 48, 72 hours - the different things that are already happening -Obviously fertilization occurs and you get two cells and then 4 cells and eventually you get a mass of cells that constitutes the blastocyst and then it gets implanted -In the video he mentioned the inner cell mass - that is really important for the study of the brain because the inner cell mass is eventually what gives rise to every part of the body -So the blastocyst gives rise to the inner cell mass and the outer cell mass - outer cell mass becomes the placenta - the part that you only need temporarily - the inner cell mass becomes the person -The cells that eventually give rise to every organ are in the inner cell mass -The mesoderm becomes the heart and the bone

Mental retardation and high radiation levels

-Very famous study was done where they studied the link between mental retardation and moms who were exposed to high radiation levels through atomic bombs dropped in hiroshima and they examined the gestational age of the developing fetus at the time of exposure -So what this is saying is that - gestational age of exposure is along the X axis and they divided people up into whether the mom was exposed to these atomic bombs when the developing fetus was between the 1st to 8th week of gestation - the 8th to 15th week or after the 15th week -What they found is that kids who were most affected by the moms exposure to radiation were those in the 8th to 15th week of gestation -Researchers thought it would be the 1st and 8th week that would be most vulnerable to radiation exposure but in fact during this time (8th to 15th week) there is no protection from teratogens and also very critical stages of the prefrontal cortex development are happening and they have contributed to the cognitive effects that are later observed in individuals who have intellectual disability -There was no link for people in 1st to 8th week of gestation and there were some association between radiation and retardation after the 15th week but not as severely as the second one where there is a lot of neural migration to the prefrontal cortex and other cortical regions -Just to sum up here that it is important to keep in mind what is happening during particular weeks of development because each event is so prescribed and all of these events are hierarchical -One needs to happen before the other one can proceed so if there is a hiccup in the development of the heart for instance that may have implications for other body parts that we are not even aware of like to maybe the development of the heart for instance

The brain is one of the most sensitive organs to stress

-We have a lot of other regions or organs in the body like the heart that is also very responsive to stress but the brain is one of the more sensitive ones

How does experience change the brain?

-We know that experience changes the brain -And when I talk about experience I could mean anything from traumatic insult when you are in utero that your mom is consuming drugs to things that happened way after birth (moved schools, learning , taking medication for something, when you first fall in love) all of that is embedded in your brain because the brain is susceptible to experience -Not every experience is going to change your brain - our brain would never be able to mature if it was constantly changing in response to every single experience -And that's what is remarkable about the brain and plasticity is that our brains are quiet good at differentiating what is going to stay - what is going to represent a new neuron or what experiences are going to lead to new neurons forming new synapses and what experiences are just going to be discarded and forgotten -And that's an important sorting that the brain has to do throughout life -There are a lot of things you wished you had remembered or your brain had a better representation of but it doesn't because the brain cant have all of our experiences represented at the neuronal level -And so a lot of this sorting of information that will lead to neural plastic changes happen in development because that is when most experiences have the most impact on how our brains our shaped -Certainly your brain undergoes plasticity well into adulthood and that's important because as you have learned more information you need to have the ability to incorporate that new information -but the majority of basic things you are going to ever learn happen during the period of early childhood development and adolescence because basic motor learning for instance happens early on in development and in order for you to keep experiencig the world

Ocular Dominance Columns: Monucular Deprivation

-What they were interested in was how this affected the ocular dominance columns -So in the visual system you have these columns - one representing the right eye , one represnting the left eye -And what they found is that - this is typical - at birth your ocular dominance columns are kind of overlapping because there is still some maturation that needs to happen -But then over time by the time you are an adult there are distinct columns that represent the left eye and the right eye -Overtime you have these distinct columns in typical development but what happens when you have an monocular deprivation experiment is that if you are depriving this eye (left one) that column begins to shrink as the neurons start to both die off and become less integrated with other neurons - stop communicating with other neurons -And look what happens to the non deprived eye - it becomes a fatter column because that one eye - the seeing eye is doing more of the work so it needs to have more neuronal resources -This is evidence of plasticity -And plasticity is adaptation to the environment -And if your environment or your circumstance is such that you only have one eye that is functional then your brain is going to say ok im going to stop wasting neural resources on the blind eye and focus in on the eye that is going to help me interact with the world

Chromosomes

-You have 23 chromosomes - 22 autosomes and the 23rd makes you either a male or a female (the sex chromosome) -and these are important in terms of thinking about variability or individual variability -Is that the genes that are located on these chromosomes - each gene has at least 2 possible versions and so that means that we all have the same genes - or genomes - but we have different versions of these genes because we may have different alleles -And alleles are what make people have different eye color, hair color - things like that but they are also what account for differences in how we develop, differences in the ability to exert cognitive control -All of those are also informed by variation in alleles across different people -And so while genotypes determine the genetic information - getting into the DNA of a particular trait - the expression of that genotype is the phenotype -each gene has at least two possible versions (one on each chromosome). These alternative states are alleles.

Synaptogenesis

-Your brain gets rid of synapses it does not need -Critical event in the maturation of the neocortex -5 distinct waves of synaptogenesis -Highly orchestrated -So what starts to happen is that you start to become stronger in a particular language and you start to eliminate the unneccessary synapses you don't need because you are not learning 5 languages you are learning 1 and so you become really good at that one at the expense of being able to learn other ones -And so synaptogenesis follows these 5 distinct waves mostly in sensory domains - so what happens is the brain gets rid of synapses it doesn't need it's a critical event in the maturation of the cortex -You have probably heard the narrative that the brain continues to develop through the mid-20's and what people are referring to is not that your brain keeps growing till your mid-20s but actually that the pruning process keeps happening till your mid-20s -That a mature brain is a pruned brain - that a matured brain is a brain that has eliminated the excess synapses in the service of strengthening the synapses it does have and does need -And that over the 25 years or so you are alive your brain is trying to figure out which synapses it needs to strengthen and eliminate the other ones -So there are 5 distinct waves of synaptogenesis that are highly orchestrated

Are the effects of stress "reversible"

-brain scan while studying for medical board exam -brain scan after medical board exam -So is this reversible? Challenging to study -Researcher did clever experiment where he took participants into scanner while they were studying for the medical exam - so before the exam they were super stressed out -He put them in the scanner and then once they took the exam and they were super happy he put them in the scanner again -And this is perfect because then you can see the effects of a stressor that was controlled -And indeed those who were more stressed out had worse performance on a cognitive task -Heres another example of knowing: this is a discrete stressor so session 1 was before they took the exam when they were stressed out and session 2 was after they took the exam -The perceived stress score was on the Y axis and clearly there was a significant difference -And this is the way it should be they should be less stressed out once they have taken the exam -And again their cognitive performance was much worse when they were stressed out vs. when they had already taken the exam -It was probably because they were so focused on the particular facts of the exam that their brain was maxed out in terms of what else they could be doing -And this makes a lot of sense if you think about when we devote a lot of neural resources to one thing its at the expense of all the other things we are working on -Like when we are in finals a lot of you may have your relationships be lacking because you have only so much capacity to devote to whatever task is being presented to you -So he measured something called functional connectivity where you are measuring how well 1 part of the brain connects to other parts of the brain -And in general as people get older and certainly medical students have really good funcitonal connectivity but what he found is that when he tested the DPFC (cognitive region) and did a functional connectivity analysis he found that in session 1 (when they were very stressed out) there was decreased connectivity between the DLPFC and all the other brain regions he studied but that this converted back to baseline once the stressor had been removed -And so this suggests that there is some reversibility - he found that this red bar reversed back to baseline after the stressor had been removed -Decreased functional connectivity in session 1 (during stress) that is reversed in session 2

Does prenatal stress influence behavior in adulthood?

-developmental pyramid -adult behavior builds or develops off of prenatal stress

Second Trimester

-fetus begins to explore his/her surroundings -So now the fetus has hands, eyes, and they can move their legs and so this allows them to interact with their surroundings they don't have much in their surroundings -So the fetus at this stage if you do an ultrasound you might see them sucking their thumb or distinctly moving their hands and legs a lot because they can - because this is new information so even before they are born they are starting to recognize aspects of their bodies that they can control - that they can use to interact

Programming effects

-prenatal stress -when a stressor acts on the organism during a sensitive period, affecting the structure and function of the brain, leading to effects that persist throughout life -And this goes back to the discussion I was just having about the difference between developmental and adult plasticity -That if the plasticity is occurring developmentally then the effects will be in the programming domain - that is the domain that is setting up the developing organism - so itll effect the structure and the function of whichever brain region is undergoing the most development at that time and lead to effects that persist throughout life -So its not the case that if you have chronic stress as a child and that chronic stress your hippocampus that once you are no longer a child that your hippocampus is no longer affected anymore no - it's the case that if you had chronic stress as a child and that affected the hippocampus that affect will kind of grow with the hippocampus - it will always be affected by the stress that happened 10 or 20 years ago -And so that's why there is a lot of conversation about how early life adversity isnt just affecting the children when they are developing it stays with them throughout their lives because it gets embedded in physical and neural development of the person -This is kind of making that point about how something that happens at the very bottom early in life or prenatally -that the pyramid is going to build on that foundaiton and so that eventually even though this person as an adult is no longer experiencing the same stress as they did prenatally the stress got under the skin of the developing organism at this time and so this is an example of how development builds on itself - you cant ignore the developmental history of an organism -That's not to say that if you have prenatal stress that you are doomed because beautifully we have plasticity and negative effects that happen as a child can also be undone or worked on and that's why the reversability of exposure to the environment is so important

Making the error vanish by changing:

-the attention-grabbing properties of the covers of the well -the attention-grabbing properties of the hiding event -the delay -the past activity of the infant -the position of the infant during hiding event of B -Here are the reasons we know its multicausal - because there are multiple ways that you can make the error vanish -In other words typically 8-10 month olds make the A not B error - they go for well A even though the ball is in well B but there are multiple ways you can eliminate that problem -If you make the attention grabbing properties of the covers of the well more salient - in other words if you make the covers of well A black and the cover of well B neon yellow its simply more attention grabbing and so babies don't make the error if you do that - so attention is also one of the causes - one of the multicausal reasons -If you make it more salient not just by the color of the cloth that covers well B but you make that property more exciting like you play a little bell or something when you put the ball in the new location the baby doesn't make the error -We have already talked about the delay (the working memory problem) if you wait 5seconds the baby makes the error if you do it immediately after the baby doesn't make the error -The experience of the infant - they have done this before they are less likely to make the error -And then the final thing that I think is really interesting that probably explains a lot of things that happen between 10 months and 12 months - typically the baby is sitting across from the experimenter - but if you lift the baby up so they have a birds eye view of well A and well B they don't make the error - that is there is something about their visual perspective that makes it hard for them to understand that the ball now went into a new location -so these are the specific things people do to make 8-10 month olds not make the error but collectively this explains multiple causes for the error -The multiple causes are the attention span is short for babies, their working memory is limited, their physical position precludes a good view of what is happening - all of these things contribute to the error

Neurulation (18-24 prenatal days)

-undifferentiated tissue becomes the brain and the spinal cord -neural plate to neural tube -When a cell is called an undifferentiated cell that means its final fate has not yet been determined -That means that its kind of a catch all kind of cell -It hasn't yet become a brain cell or a skin cell or a heart cell - that's what undifferentiated means its kind of like a blank slate -And then induction refers to the process of transforming undifferentiated tissue - that is it's the process of making tissue specific to one aspect of the body, one aspect of the brain -Its most important for our purposes for when we form a neural tube - the neural tube goes on to create the spinal cord and that's crucial and happens very early on in development -So before we have a neural tube we have something called a neural plate -Within the neural plate you will see these three components: the ectoderm, mesoderm, and endoderm -And then at some point within the first few weeks there is something called neurulation and that is when the spinal cord goes from being a flat plate into a tube and that also happens through genetic information -People have worked rigurously to figure out the exact genes that cause this transformation from neural plate to neural tube -So slowly it becomes a half circle then eventually it becomes a tube and this process happens through TNF's -And people have determined that by removing a particular gene and seeing what happens - and what they have found is if you remove transforming growth factors (TNF's) than they fail to develop a spinal cord -And it doesn't happen so often anymore - but an atypical type of development that happens when the neural tube doesn't close is spina bifida - it's the case that the neural tube fails to close depending on which end the neural tube fails to close leads to different phenotypes -If the anterior end fails to close it causes a miscarriage -If the posterior end fails to close than it leads to spinabifida and the embryo is viable which means it proceeds and there is birth but it can have a host of different outcomes from needing neural tube spinal cord surgery to other kinds of deficits -This is an example of how we make something more with something less - the body starts with the neural plate and then through its own self organization it makes something much more - a much more important organ

Not all plasticity is the same

1. Developmental plasticity 2. Adult Plasticity -Are the plastic processes that operate during development the same as those that operate in adulthood? -Does experience influence the brain in the same way across the lifespan? -there are two types of plasticity -That is that the brain can change in response to the environment but depending on what developmental stage it is at it will have different outcomes in the brain -Developmental plasticity is mostly what is happening when the organism is in development whereas adult plasticity refers to mostly learning mechanisms - so when you learn something as an adult whether you learn a new concept in a higher advanced math class or you pick up some type of hobby that type of experience is working under a different brain structure

Environmental Complexity Paradigm

1. Environmental Complexity (EC) Animals -Housed in groups in large cages -Access to objects to manipulate -Exposure to challenges (mazes) 2. Social Cage (SC) Animals -Housed in pairs in standard cages -No objects 3. Individual Cage (IC) Animals -Housed alone -No objects -The environmental complexity paradigm is one in which you give the animals a lot of information in their environment - running wheel, other animals, maze -And so you compare those animals to animals who are either social cage animals - they are housed in pairs but have no objects -Or individual cage animals who are in the cage alone with no other animal -So again three conditions: environmental complexity, social cage (bare cage but have another animal in there), and then individual cage (alone) -Animals in enriched environment (EC) perform better on complex tasks than animals reared in SC or IC -Unsurprisingly what they find is that the animals in the enriched environment (had toys to play with) showed better outcomes -This outcome is about learning but you could put anything here on the Y axis and what they find is that the animals in the enriched environment do much better - their behavior is better they are better able to learn they are better able to socialize they are better able to process any type of information -And the reason for that is because the experience of being in an environmentally enriching environment leads to differences in morphology

Two categories of plasticity for the storage of experience-related information

1. Experience-expectant: -The organisms is EXPECTING input -Species have evolved neural mechanisms to take advantage of experiences that typically occur (e.g. visual input) to shape developing motor and sensory systems -Timing occurs at roughly the same time among individuals 2. Experience-dependent: -Experience/input that is unique to the individual -Experience differs in timing among individuals -As opposed to what i was saying before about how there is some variability to when kids learn to walk and talk there is not that much variability as to when your visual cortex gets developed in your brain when you are in utero its a pretty tight window because following an evolutionary template of getting your brain set up in order to be ready for birth -When i say its based on evolutionary history it means that the brain is planning for what will likely happen - what will likely happen when you are born is you will receive a lot of visual information - just based on every other member of the species and so the organism should be prepared to process that visual information - and so thats just based on probability -So for instance if it has been raining Monday-Thursday what are you going to leave the house with on Friday - an umbrella - you are expecting it to rain simply because thats what has been happening everyday until now - however it could be the case that it actually doesnt rain so you dont need your umbrella and so our brains are also equipped to deal with the unexpected so even if we expect that everyone will have the same abilities in terms of processing visual information there are some individuals who may be born blind or with a diminished capacity to process visual information and so in that case the visual cortex that has been built up will start to redirect neural resources to start to make a different sensory modality like the auditory cortex for ex -And so the ability to adapt is what characterizes experience dependent mechanisms - so experience expectant is something that all members of the species should expect whereas experience dependent is what allows for experiences that are unique to each individual -And so experience dependent mechanisms really dont play a role in gestational development - right when you were born we all had different experiences that only continue to diversify as we get older - as we are reared by different kinds of parents - as we go to different schools you have experiences that are unique to you so your brain is able to adapt to those unique experiences that also differ in timing -Not everyone learns to read at the same age - not everyone learns to drive at the same time -All of those things have to allow for individual variation

Genetic variability contributes to behavior/trait variability

1. Rate of Development 2. Individual traits 3. Abnormal Development -There are three main contributions of genetic variability that are built in for us -one is the rate of development: although we all kind of have the same milestones at roughly the same age there is individual variation -Most kids start to walk and talk at age 1 but some start earlier around 10 months and some are well beyond that at a year and a half so that range in why some people reach certain milestones earlier is in part attributed to this genetic variability and behavioral variability 2. Individual traits make people different from one another 3. This variability accounts for abnormal development that most typically occurs in utero

Causes of Allostatic Load

1. Repeated frequency of stress responses to multiple novel stressors 2. Failure to habituate to repeated stressors of the same kind 3. Failure to turn off each stress response in a timely manner due to delayed shut down 4. Inadequate responses that leads to compensatory hyperactivity of other mediators (other brain regions) -This lists what i already said about the causes of an overactive stress system

What are the effects of postnatal stress on development in humans?

Adoption Study -"Dose-dependent" effect of poor caregiving on brain development -78 international children who were adopted to the U.S. -Mean age of adoption (in months): 19.2 months (range: 2.5-60 months) -In the states there have been similar studies in kids that have been adopted -That is kids who spent some amount of time in orphanage care abroad -So this study was conducted in almost 80 kids who were born internationally but then adopted to the US -And the reason its called the dose dependent effect is because they were adopted to the US some as young as 2 months and some as old as 60 months of age -And there is a lot of development happening during that time in those 5 years -So some kids spent two months in orphanage care abroad and some kids spent 5 years abroad -And so that makes a big difference in the type of experience they were getting in the orphanage care but also the deprivation of not having a stable caregiving environment -Children who spent more time in orphanage had larger amygdala -She brought the kids to the lab and brain scanned all of them and what she found is that the kids who spent more time in orphanage care had larger amygdala than the kids who had never been in orphanage care or the kids who were adopted early -And so this argues for the dose dependent effect - that the length of time is very meaningful to brain development and in particular to the amygdala -Because she also examined the hippocampus and the caudate - and those latter brain regions didn't show differences based on how long the kids were in orphanage care -So the amygdala seems to be particularly sensitive to these suboptimal rearing experiences -Children who spent more time in orphanage had larger amygdala and higher anxiety -Heres a clear picture of that -So age adopted out of orphange is on the X axis - so here we have the 2 year old and the 5 year old and we have significant correlation here that the size of the amygdala was bigger in the kids that spent more time in orphanage care and smaller in the kids who spent basically no time in orphanage care -Perhaps this is because they have had higher activity during that time that their amygdala was undergoing a lot of stimulation in the orphanage care - they didn't have an attachment figure often in the orphanage - so the way these orphanges are run is that they have a lot of caregivers a lot of people working there and once the person finishes their shift they leave and so what happens is that that child doesn't have a chance to have a bonding interaction with any one caregiver and that's highly stressful for especially young infants -The other thing to note about this data is that there is another correlation -Here amygdala volume is on the X axis and anxiety scores are on the Y axis so the kids who bigger amygdala also had greater symptoms of anxiety and that was also related to how long they were in the orphanage -So there seems to be a relationship between amygdala volume and anxiety -Even the kids who were adopted late at 5 year olds were adopted into high quality parenting here in the US - people who adopt often have a very long process of adoption and they really are invested in adopting these children and so even if the first 5 years of life were in a suboptimal environment they come to an environment that is better and yet they still show these effects years later - when they were tested at a later point they were teenagers so had been with their adoptive parents for years and they still showed some of these effects

Critical Period/Sensitive Period

Critical Period: -A limited period of time when experience can influence brain development (usually in sensory and motor domains) -Particular input is expected Sensitive Period: -Heightened sensitivity to certain environmental stimuli -Not as rigidly tied to a specific age -(e.g. learning a new language) -There are times in development where your brain is more receptive to learning new things -How is it that you can learn language and then over time your brain stops being as receptive to learning language -The window or timeframe which you are more primed to learn language is called the critical period -A critical period and the reason theres a window here is its often called a critical window with the idea being that anything you experience after the window shuts - after the window of opportunity shuts makes it much harder to learn that thing like language -A critical period is the particular window in time where experience can influence brain development -Most of this refers to sensory and motor domains - and the most famous experiments are in visual processing or visual development -And in this case the particular input (visual input or exposure to visual information) is expected - that is your brain expects to get visual input within a very narrow window of time and if you don't get that experience or that visual information that window shuts and then it is no longer possible for your visual cortex in this case to develop because your window has shut -That is the critical period - it is rigid -There is a distinction between critical period and sensitive period -Theyy both refer to periods in development when your brain is more heightened and receptive to information but where as the critical period is more rigid and the organism expects particular input a sensitive period refers to greater sensitivity to certain environmental stimuli but its not rigidly tied to a particular age -So language learning occurs to whats called the sensitive period because you are more receptive to learning your parents language but it doesn't mean that if you don't get a different language within the first or second year of life that youll never be able to learn that language -You may not be as fluent as the person who has learned that language since birth but it doesn't mean you are unable to learn it - you are able to still pick up japanese or whatever it is -But you cant make up for never having had visual information until you got to college -The terms 'Sensitive'/'Critical' Periods do not describe the mechanism by which this phenomenon occurs -Mechanism: the way something happens, the process by which change occurs -For many years these terms sensitive and critical were what we used to describe neuroplasticity in the brain -But a researcher was someone who was unsatisfied with these terms because they don't describe the mechanism by which this happens -Why is it that case that we are more sensitive to particular things? How does it happen and based on evolutionary time why does it make sense that we can adapt in certain domains like language but are pretty rigid in domains like visual information or auditory information? -So he coined these new terms to replace sensitive period -This is really important to truly understand contemporary developmental neuroscience theory you have to understand the terms experience expectant and experience dependent

Summary

Developmental Plasticity -Building a new house -Experience-expectant processes produce a surplus of synapses which are pruned back by experience -Relatively irreversible -Very time sensitive -Abnormal input leads to abnormal neural pattern formation -Just to summarize this lecture: developmental plasticity is really dependent on experience expectant process that produce... (as your brain figures out what it needs to keep and what it can let go of) -Its relatively irreversible and very time sensitive in that if your brain expects to receive something and it doesn't it will start to develop new ways to compensate for that deficit Adult Plasticity -Remodeling (adding-on) an existing house -Experience-dependent synapse formation in response to events -Sometimes reversible -Whereas adult plasticity is remodeling of an existing network -And you have synapse formation that you generated based on your own individual experience and sometimes it is reversible as in the example of learning to juggle or learning some skill and then not training on that skill for awhile you can remove that plasticity

Experience-expectant vs. Experience-dependent

Experience-expectant: -Very early in life -"pruning" (removal) of excess synapses following experience-expectant events Experience-dependent: -Later in development and adulthood -Generation of new synapses based on need -Generally experience expectant mechanisms happen early in life... -They prune away excess synapses - thats the mechanism for plasticity -Whereas experience dependent happens later in life and persists longer and its based on the generation of new synapses that are rooted in the need or the new experiences that you need to incorporate -Expectant processes happen much earlier in life and if the organism doesnt get experiences it expects there is atypical or aborent development -Whereas experience dependent is typically more associated with individual development that is particular to that individual