PSY 435 unit 7 full
enriched environment, enhanced development
(A) A complex environment for a group of about six rats allows the animals to move about and to interact with one another and with toys that are changed weekly. (B) Representative neurons from the parietal cortex of a laboratory-housed rat and a complex-environment-housed rat; the latter has about 25 percent more dendritic space for synapses.
estrogens
Variety of sex hormones responsible for the distinguishing characteristics of the female.
neuron seeking out a path
(A) At the tip of this axon, nurtured in a culture, a growth cone sends out filopodia seeking specific molecules to guide the axon's direction of growth. (B) Filopodia guide the growth cone toward a target cell that is releasing cell adhesion or tropic molecules, represented in the drawing by red dots.
Neuronal migration
- (A) Neuroscientists hypothesize that the cortical map is represented in the subventricular zone. - (B) Radial glial fibers extend from the subventricular zone to the cortical surface. - (c) Neurons migrate along the radial glial fibers that take them from the proto map in the subventricular zone to the corresponding region in the cortex.
stages in Brain development
- 1 Cell birth (neurogenesis; gliogenesis) - 2 Cell migration - 3 Cell differentiation - 4 Cell maturation (dendrite and axon growth) - 5 Synaptogenesis (formation of synapses) - 6 Cell death and synaptic pruning - 7 Myelogenesis (formation of myelin)
three perspectives by which scientists view brain development
- 1. Structural development can be correlated with emerging behaviors. - 2. Behavioral development can be predicted by the underlying circuitry that must be emerging. - 3. Research can focus on factors such as language, injury, or socioeconomic status (SES) that influence both brain structure and behavioral development.
correlations between gray matter thickness and behavior
- A) Red shading corresponds to regions showing significant cortical thinning correlated with improved motor skills. (B) White shading corresponds to regions showing significant cortical thickening correlated with improved language skills. (c) Red shading shows regions of decreased cortical thickness correlated with improved vocabulary scores.
motor development and its effect on language
- Although language skills and motor skills generally develop in parallel, the capacity for language depends on more than the ability to make controlled movements of the mouth, lips, and tongue. Precise movements of the muscles controlling these body parts develop well before children can speak. Furthermore, even when children have sufficient motor skill to articulate most words, their vocabulary does not rocket ahead but rather progresses gradually.
synaptic development
- As with all stages of brain development, only the general outlines of neuronal connections in the brain are likely to be genetically predetermined, the vast majority controlled by enviro cues. - A human fetus displays simple synaptic contacts in the fifth gestational month. By the seventh month, synaptic development on the deepest cortical neurons is extensive. After birth, synapse numbers increase rapidly. In the visual cortex, synaptic density almost doubles between ages 2 months and 4 months and then continues to increase until age 1 year.
Social economic status (SES) effect on Intelligence-
- At 36 months of age, on average, the vocabulary of children from a low-SES environment is less than one-third that of high-SES children (400 versus 1200 words). - is hypothesized to result from less direct conversation with caregivers and less reading to the children by caregivers. The weaker language skills demonstrated by children of low SES is related to the size of cortical language areas as early as age 5 years - an important point is that SES itself is not the variable driving effects on language and brain development. Rather, SES is likely a proxy for the opportunity to learn language,.
prenatal Development of the Human Cerebral Cortex
- Brain weight and body weight increase rapidly and in proportion. The cortex begins to form about 6 weeks after conception, with neurogenesis largely complete by 25 weeks. Neural migration and cell differentiation begin at about 8 weeks and are largely complete by about 29 weeks. Neuron maturation, including axon and dendrite growth, begins at about 20 weeks and continues until well after birth.
language development
- Children start to form a vocabulary by 12 months. This 5-to-10-word repertoire typically doubles over the next 6 months. - By 2 years, vocabulary will range from 200 to 300 words that include mostly everyday objects. In another year, vocabulary approaches 1000 words and begins to include simple sentences. - At 6 years, children boast a vocabulary of about 2500 words and can understand more than 20,000 words en route to an adult vocabulary of more than 50,000 words.
example of time dependent effects
- Damage to the rat's frontal cortex on the day of birth leads to cortical neurons with simple dendritic fields and sparse growth of spines in the adult (left). In contrast, damage to the frontal cortex at 10 days of age leads to cortical neurons with expanded dendritic fields and denser spines than normal in adults (right).
fertilization
- Development begins at fertilization (day 1), with the formation of the zygote. On day 2, the zygote begins to divide. On day 15, the raised embryonic disc, essentially primitive body, begins to form.
Romanian orphans study highlight refresher: basics
- Elinor Ames, Simon Fraser University - Compared - Canadian children ('regular') - Romanian - in orphanage for 8 months - Romanian - in hospitals for 4 months - followed over a 10 year period. - Time of adoption: 78% of Romanian children delayed in many areas (gross motor, cognition, social-emotional) - Romanian orphan group fared worst, hospital adoption cases fared a bit better. - At age 10 years: Orphan group had lower IQ scores, poorer attention abilities & school achievement than other groups; more learning disabilities as well, but those with more nurturing at age 4 had better attention skills at age 10. - lots of success as well- - (great individual variability) - High self concepts - Good parental support - Parental satisfaction - 2/3 of kids said to be fairing well overall.
the microbiome: basics-
- an important part of the ENS, the bacteria in the gut with which the ENS interacts. About 1014 microbiota populate the adult gut, which means that microbiota outnumber the host body cells by a factor of 10. - in utero, the fetus's gut is sterile. It is only at birth that trillions of microbes from the mother's vaginal and anal fluids, and later from her skin, invade the baby's body and start to grow.
schizophrenia disturbances in brain development: basics
- Evidence is increasing that the abnormalities observed in schizophrenic brains are associated with disturbances of brain development. - has been suggested that at least a subgroup of those with schizophrenia underwent either environmental insults or some type of abnormal gene activity in the fourth to sixth month of fetal development. - These events are thought to result in abnormal cortical development, particularly in the frontal lobes. Later in adolescence, as the frontal lobes approach maturity, the person begins to have symptoms deriving from this abnormal prenatal development.
Identifying Influences on Brain and Behavior
- From this perspective, the mere emergence of a fully developed brain structure is not enough. We must also know the events that shape how that structure functions and produces behaviors. Some events that influence brain function are sensory experience, injuries, and the actions of hormones and genes. - Logically, if one factor influences behavior, then the brain structures changed by that factor are those responsible for the behavioral outcomes.
the microbiome: relation to mental illness
- Many neurodevelopmental disorders, including autism, may be related to an atypical microbiome early in life - in a study with mice that had ASD, who produce few social auditory vocalizations, about one-third the normal levels. Manipulation of their gut bacteria restored the vocalizations to normal levels, demonstrating that gut bacteria can alter behavior.
disproving the idea that kids a miniature adults
- Mature adults with acquired frontal lobe injuries also fail to perform well on the Tower of Hanoi test. Such evidence reinforces the idea that children are not miniature adults who simply need to learn the "rules" of adult behavior. A child's brain is vastly different from an adult's, and the brains of children at different ages are not really comparable either.
The trajectory of frontal lobe development correlates with adult intelligence
- Philip Shaw and his colleagues used a longitudinal design, administering multiple structural MRIs to participants over time. The results show that it is not the thickness of the frontal cortex in adulthood that predicts IQ score but rather the change in trajectory of cortical thickness . Children who score highest in intelligence show the greatest plastic changes in the frontal lobe over time. These changes are likely to reflect strong epigenetic influences.
autism spectrum disorder (AsD) basics
- Range of cognitive symptoms from mild to severe that characterize autism; severe symptoms include greatly impaired social interaction, a bizarre and narrow range of interests, marked abnormalities in language and communication, and fixed, repetitive movements.
neuronal contrast
- Representative dendritic branches from cortical neurons in a child of typical intelligence (left) and a developmentally disabled child (right), whose neurons are thinner and have far fewer spines.
Stem cells and neural replacement
- Sam Weiss and his colleagues (1996) discovered that stem cells remain capable of producing neurons and glia not just into early adulthood but even in an aging brain. This important discovery implies that neurons that die in an adult brain should be replaceable. But neuroscientists do not yet know how to instruct stem cells to replace them.
motor development
- Shortly after birth, infants are capable of flexing their arms in such a way that they can scoop something toward their body, and they can direct a hand, as toward a breast when suckling. Between 1 and 3 months of age, babies also begin to make spontaneous hand and digit movements consisting of almost all the skilled finger movements they will make as an adult, a kind of motor babbling. - Between 8 and 11 months, infants' grasping becomes more sophisticated as the pincer grasp, employing the index finger and the thumb, develops. The pincer grasp is significant developmentally: it allows babies to make the very precise finger movements needed to manipulate small objects.
experiment 8-1: In what sequence do the forebrain structures required for learning and memory mature?
- Study the pic - Results: Both human and monkey infants learn the concurrent-discrimination task at a younger age than the nonmatching-to-sample task. - conclusion: Neural structures underlying the concurrent-discrimination task mature sooner than those underlying the nonmatching-to-sample task
prenatal stages
- Zygote- Fertilization to 2 weeks - Embryo- 2 to 8 weeks - Fetus- 9 weeks to birth
Correlating Emerging Brain structures with emerging Behaviors
- can look at nervous system's structural dev and correlate it with emergence of specific behaviors. for example, the dev of certain brain structs links to motor dev of grasping or crawling in infants and as the struct mature's their functions emerge and develop and are manifested by observable behaviors. - Neural structs that dev quickly , such as the visual system, exhibit their functions sooner than structs that dev more slowly such as those used for speech. - Because the human brain continues to develop well into adulthood, some abilities emerge or mature rather late. Some cognitive behaviors controlled by the frontal lobes are among the last to develop.
Correlating Emerging Behaviors with neural Maturation
- can scrutinize behavior for the emergence of new abilities, then, infer underlying neural maturation. for example as language emerges in young kids, we expect to find , and do find, corresponding changes in neural structs that control language. - the same is for frontal lobe development As frontal lobe structures mature though kid to adult, , we look for related changes behavior. We can also do the reverse: because we observe new abilities emerging in the teenage years and even later, we infer that they must be controlled by late-maturing neural structures and connections.
Unique aspects of frontal lobe development
- frontal lobe is the last brain region to mature. - frontal lobe maturation extends far beyond its age 20 boundary, including in the dorsolateral prefrontal cortex. - dendritic spine density, a good measure of the number of excitatory synapses, is two to three times greater in children than in adults and that spine density begins to decrease during puberty.
roles of synaptic pruning
- may allow the brain to adapt more flexibly to environmental demands. - may also be a precursor related to different perceptions that people develop about the world.
Hebb's dog study on effect of restricted experiences
- placed young Scottish terriers in the dark with as little stimulation as possible and compared their behavior to that of dogs raised in a typical environment. - When the dogs raised in the barren environment, were later removed from it, their behavior was highly unusual. virtually showing no reaction to people or animals and appeared to have lost pain sensation, would not even respond to being poked with needles. - when given the dog version of the intelligence test for rats, these dogs performed terribly and were unable to learn some tasks that dogs raised in more stimulating settings learned easily.
gene/DNA methylation
- processes where a methyl group (CH3) attaches to the nucleotide base cytosine lying next to guanine on the DNA sequence. It is relatively simple to quantify gene methylation in different phenotypes, reflecting either an increase or a decrease in overall gene expression. - alters gene expression dramatically during development - Prenatal stress can reduce gene methylation by 10 percent.
autism stats
- rate has been rising over last 40 years. going from 1 in 2000 to 1 in 68 or 1 in 50. - the cause of the increased incidence is unknown but may involve changes in dx criteria, dx at younger ages,, and epigenetic influences. - 4 times as prevalent in boys than girls. - brains are remarkably typical.
testing cognitive development: the tower of Hanoi
- shows how planning skills can be measured in the laboratory. - is a mathematical puzzle consisting of three rods and several different-sized discs. The task is to match the goal in as few moves as possible, obeying two rules: (1) only one disc may be moved at a time; (2) no disc may be placed on top of a smaller disc.
Romanian orphans study highlight refresher: major conclusion
- the human brain may be able to recover from a brief period of extreme deprivation in early infancy, but periods longer than 24 months produce significant developmental abnormalities that cannot be overcome completely.
dendritic development
- two events occur during this process, dendritic arborization ,AKA branching, and the growth of dendritic spines. - Dendrites in newborns start as individual processes protruding from cell body, then in first 2 years begin to dev complex extensions and the branches begin to form spines where most dendrites are located. begins prenatally in humans and continues well after birth.
increased cortical activation for second languages
- using both PET and fMRI to determine if native and second languages differ in cortical activation, found that: - while there is great overlap, when asked to repeat words, the second language shows greater activation in motor regions such as the striatum and cerebellum as well as in the frontal and temporal language regions. leading to idea that second language puts greater articulation demands on the speaker.
gray matter thickness
Brain maps showing the statistical significance of yearly change in cortical thickness measures taken from MRIs. Shading represents increasing ,white, or decreasing, red, cortical thickness.
neurotrophic factor
A chemical compound that signal cells to develop in particular ways and supports growth and differentiation in developing neurons and may act to keep certain neurons alive in adulthood.
formation of the neural tube
A long depression, the neural groove, first forms in the neural plate. By day 21, the primitive brain and neural groove are visible. On day 23, this is forming as the neural plate collapses inward along the length of the embryo's dorsal surface. .
the enteric nervous system-
AKA ENS, sends information to the brain that affects our mental state.
progenitor cell
AKA precursor cell, Derived from a stem cell; it migrates and produces a neuron or a glial cell and eventually produces the neuroblasts and glioblasts
critical period
AKA sensitive period, Developmental window during which some event has a long-lasting influence on the brain; also, sensitive period. important. A time during which brain development is most sensitive to a specific experience .
neuronal maturation
After neurons migrate to their destination and differentiate, they begin to mature by (1) growing dendrites to provide surface area for synapses with other cells and (2) extending their axons to appropriate targets to initiate synapse formation
Glial development
Astrocytes and oligodendrocytes begin to develop after most neurogenesis is complete and continue to develop throughout life. CNS axons can function before they are myelinated by oligodendria, but healthy adult function is attained only after myelination is complete. Consequently, myelination is a useful rough index of cerebral maturation.
dorsolateral prefrontal cortex (DLPFC)
Brodmann areas 9 and 46; makes reciprocal connections with posterior parietal cortex and the superior temporal sulcus; responsible for selecting behavior and movement with respect to temporal memory.
Origin of brain cells
Cells in the brain begin as multipotential stem cells, develop into precursor cells, then produce blasts that finally develop into specialized neurons or glia.
sex differences in brain volume
Cerebral areas related to sex differences in the distribution of estrogen (orange) and androgen (green) receptors in the developing brain correspond to areas of relatively larger cerebral volumes in adult .
androgen
Class of hormones that stimulates or controls masculine characteristics.
amblyopia
Condition in which vision in one eye is reduced as a result of disuse; usually caused by a failure of the two eyes to look in the same direction.
sexual differentiation in the human infant
Early in the indifferent stage, male and female human embryos are identical (top). In the absence of testosterone, female structures emerge (left). In response to testosterone, genitalia begin to develop into male structures at about 60 days (right). Parallel changes take place in the embryonic brain in response to the absence or presence of testosterone.
example of the strength of imprinting
Ethologist Konrad Lorenz followed by goslings that imprinted on him. He was the first object that the geese encountered after hatching, so he became their "mother."
anencephaly
Failure of the forebrain to develop.
Flechsig myelinating hypothesis
Flechsig hypothesized that the earliest-myelinating areas control simple movements or sensory analyses, whereas the latest-myelinating areas control the highest mental functions. MRI analyses of myelin development in the cortex show that white matter thickness largely does correspond to the progress of myelination, confirming Flechsig's ideas. Myelination continues until at least 20 years of age, which contrasts total brain volume, gray matter volume, and white matter volume during brain development in females and males.
timing of brain damage changes how devastating the effect is
For humans, the worst time appears to be in the last half of the intrauterine period and the first couple of months after birth. Rats and cats that are injured at a comparable time have a significantly smaller brain than average, and their cortical neurons show general atrophy relative to healthy brains, Behaviorally, these animals appear cognitively deficient over a wide range of skills.
Embryonic Vertebrate Nervous system
Forebrain, midbrain, and hindbrain are visible in the human embryo at about 28 days, as is the remaining neural tube, which will form the spinal cord.
imprinting
Formation of an attachment by an animal to one or more objects or animals at a critical period in development. a critical period during which an animal learns to restrict its social preferences to a specific class of objects, usually the members of its own species.
apoptosis
Genetically programmed cell death. accounts for the death of overabundant neurons, but it does not account for the synaptic pruning from cells that survive.
growth cone
Growing tip of an axon. as growth cones extend, they send out shoots, analogous to fingers reaching out to find a pen on a cluttered desk. When one shoot, a filopod (pl. filopodia), reaches an appropriate target, the others follow. are responsive to cell adhesion molecule's and tropic molecule's.
neural Darwinism
Hypothesis that the processes of cell death and synaptic pruning are, like natural selection in species, the outcome of competition among neurons for connections and metabolic resources in a neural environment.
preformation
Idea by Seneca the Younger that a human embryo is an adult in miniature, and thus the task of development is simply to grow bigger. this was a popular idea that stuck around for centuries, but lost traction in the mid 1800s as people realized embryos look nothing like people.
The frontal lobe is especially sensitive to epigenetic influences
In a study of more than 170,000 people, Robert Anda and colleagues show that such aversive childhood experiences (ACEs) as verbal or physical abuse, a family member's addiction, or loss of a parent are predictive of physical and mental health in middle age. hypothesize that early aversive experiences, such as sexual assault, promote these ACE-related susceptibilities by compromising frontal lobe development. Abnormal frontal lobe development would make a person less likely to judge such a situation as dangerous.
neuronal maturation in Cortical Language areas
In postnatal cortical differentiation—shown here around Broca's area, which controls speaking— neurons begin with simple dendritic fields that become progressively more complex until a child reaches about 2 years old. Brain maturation thus parallels a behavioral development: the emergence of language.
hebb williams Maze
In this version of the maze, a rat is placed in the start box (S) and must learn to find the food in the goal box (G). Investigators can reconfigure the walls of the maze to set new problems. Rats raised in complex environments solve such mazes much faster than do rats raised in standard laboratory cages.
schizophrenia disturbances in brain development: pyramidal cell orientation
LOOK AT PIC, in the hippocampus of (A) a healthy brain and (B) a schizophrenic
subventricular zone
Lining of neural stem cells surrounding the ventricles in adults.
progressive changes in Cortical Thickness
MRI scans track the maturation of gray matter in typical development, revealing the length and pattern of maturation from the back of the cortex to the front. Cortical thinning and increased surface area progress together. cortex typically thins from age 5 to 20 with sole exception for major language related regions.
sex differences in Brain development
Mean brain volume by age in years for males ,green, and females ,orange. Arrows above the curves indicate that females show more rapid growth than males, reaching maximum overall volume ,A, and gray matter volume ,B, sooner. Decreasing gray matter corresponds to cell and synaptic loss. Increasing white matter volume ,c, largely corresponds to myelin .
netrin
Member of the only class of tropic molecules yet isolated in the brain.
chemoaffinity in the visual system
Neurons A through G project from the retina to the tectum in the midbrain. The activities of adjacent neurons (C and D, say) are more likely to coincide than are the activities of widely separated neurons such as A and G. As a result, adjacent retinal neurons are more likely to establish permanent synapses on the same tectal neurons. By using chemical signals, axons grow to the approximate location in the tectum (top). The connections become more precise with the passage of time (bottom).
possible ways to replace neurons
One possibility is to make use of signals that the brain typically uses to control stem cell production in adults. For example, the level of the neuropeptide prolactin increases when female mice are pregnant and stimulates the fetal brain to produce more neurons These naturally occurring hormonal signals have been shown to replace lost neurons in brain-injured laboratory animals.
radial glial cell
Path making cell that a migrating neuron follows to its appropriate destination.
neural plate
Primitive neural tissue that gives rise to the neural tube. forms after 21 days or 3 weeks
filopod (pl. filopodia)
Process at the end of a developing axon that reaches out to search for a potential target or to sample the intercellular environment.
masculinization
Process by which exposure to androgens (male sex hormones) alters the brain, rendering it identifiably male.
glioblast
Product of a progenitor cell that gives rise/ mature to different types of glial cells.
chemoaffinity hypothesis
Proposal that neurons or their axons and dendrites are drawn toward a signaling chemical that indicates the correct pathway. Each cell has an identifiable biochemical label. Presumably, incoming axons seek out a specific chemical, and consequently land in the correct general midbrain region.
neural stem cell
Self-renewing multipotential cell that gives rise progenitor cells and to any of the different types of neurons and glia in the nervous system. when it divides, it produces two of itself, one dies and the other divides again, a processes that continues on for ones whole life.
testosterone
Sex hormone secreted by the testes and responsible for the distinguishing characteristics of the male. stimulates development of male reproductive organs and later, in puberty, the appearance of male secondary sexual characteristics such as facial hair and deepening of the voice.
prenatal Brain development
The developing human brain undergoes a series of embryonic and fetal stages. You can identify the forebrain, midbrain, and hindbrain by color as they develop in the course of gestation. At 6 months, the developing forebrain has enveloped the midbrain structures.
progress of myelination
The fact that the light-colored zones are very late to myelinate led Flechsig to propose that they are qualitatively different in function from those that mature earlier.
Embryos and Evolution
The physical similarity of embryos of different species is striking in the earliest stages of development, as the salamander, chick, and human embryos in the top row show. This similarity led to the conclusion that embryos are not simply miniature versions of adults.
Frontal lobe development and IQ score
The trajectory of frontal lobe development from ages 7 to 16 years correlates with dynamic changes in cortical thickness. Colors on the scans scale to the magnitude of differences between individuals with average and superior intelligence. Purple shows thinner cortex in the individuals with higher IQ scores; red, yellow, and green show progressively increasing cortical thickness in those individuals. At age 7, they have a thinner frontal cortex that rapidly thickens to peak at age 13, then wanes .
ocular dominance columns
Typically in the postnatal development of the cat brain, axons from each eye enter the cortex, where they grow large terminal arborizations. (L, left eye; R, right eye).
sudden infant death syndrome (siDs)
Unexplained death while asleep of a seemingly healthy infant less than 1 year old.
gene expression
a formerly dormant gene is activated so that the cell makes a specific protein.
basic fibroblast growth factor (bFGF, or FGF-2)
a neurotrophic factor that stimulates progenitor cells to produce neuroblasts.
epidermal growth factor (EGF)
a neurotrophic factor that when added to the stem cell culture stimulates production of progenitor cells.
neuroblast
a non dividing cell , Product of a progenitor cell that gives rise / mature to any of the different types of neurons.
adolescent onset of mental disorders
age of onset differs across disorders. However, anxiety disorders, psychoses (including schizophrenia), bipolar disorder, depression, eating disorders, and substance abuse most commonly emerge by or during adolescence. neurobiological and associated behavioral changes linked with the period we define as adolescence are designed to optimize the brain for challenges that lie ahead in adulthood. But the brain's plasticity in adolescence can also make it vulnerable to psychopathologies that can endure for the rest of the individual's life.
cell adhesion molecule (cAM)
are cell-manufactured molecules that either lie on the target cell's surface or are secreted into the intercellular space. Some provide a surface to which growth cones can adhere, hence the name cellular adhesion molecule; others serve to attract or repel growth cones.
development of the grasping response in infants
at 2 months old, Orients hand toward an object and gropes to hold it. at 4 months, Grasps appropriately shaped object with entire hand. at 10 months, Uses pincer grasp with thumb and index finger opposed.
Rett syndrome
autism sub type characterized by poor expressive language and clumsy hand use, almost exclusively affects girls.
Asperger syndrome
autism sub type distinguished by an obsessive interest in a single topic or object to the exclusion of nearly any other. Children with Asperger are socially awkward and also usually have delayed motor skill development.
how a stem cell knows what to become
certain genes are expressed by a signal, and those genes then produce a particular cell type. - The specific signals for gene expression are largely unknown but probably are chemical, and they form the basis of epigenetics via such as common processes of gene/DNA methylation, or histone modification. - The chemical environments needed to trigger cellular differentiation could be produced by the activity of neighboring cells or by chemicals, such as hormones, that are transported in the bloodstream. - The differentiation of stem cells into neurons must require a series of gene-activating signals.
neural tube
formed after the neural plate folds to form the neural groove, which then curves into this. Structure in the early stage of brain development from which the brain and spinal cord develop. the cells that form this can be thought of as the nursery for the rest of the central nervous system. The open region in the tube's center remains open and matures into the brain's ventricles and the spinal canal.
Stage I , of Piaget's stages of cognitive development, the sensorimotor period
from birth to about 18 to 24 months of age. During this time, babies learn to differentiate themselves from the external world, come to realize that objects exist even when out of sight, and gain some understanding of cause and effect.
Stage IV of Piaget's stages of cognitive development, the period of formal operations
is attained sometime after age 11. Children are now able to reason in the abstract, not just in concrete terms.
how fine tuning of neural placement is achieved
is believed to be activity dependent. Because adjacent receptors tend to be activated at the same time, they tend to form synapses on the same neurons in the midbrain after chemoaffinity has drawn them to a general midbrain region.
causes of developmental disability
look at table
cellular commitment
precursor cells have unlimited possibilities, but as they develop, interacting genetic, maturational, and environmental influences increasingly steer them toward developing into a particular cell type. look at diagram
tropic molecule
produced by the targets the axons' growth cones are seeking (tropic means moving toward; pronounced as trope, not tropical), essentially tell growth cones to come on over here. They likely also tell other growth cones seeking different targets to keep away.
how the correlation causation problem effects brain and behavior studies
raises red flags in brain and behavior studies, because research in behavioral neuroscience, by its very nature, is often based on correlations. Nevertheless, correlational studies, especially of development, have proved a powerful source of insight into the principles of brain and behavior.
donald hebb on experiences influence on intelligence
ran a test with lab rats, one group grew up in his kitchen, and the control grew up in standard lab cages. gave both groups a rat-specific intelligence test that consisted of learning to solve a series of mazes, collectively known as Hebb-Williams mazes. Home-reared rats performed far better on these tasks than caged rats did. , bringing him to the conclusion that experience must influence intelligence, and as such ones environment that they grow in will influence their intelligence.
injury to developing brains is not always devastating
researchers have known for more than 100 years that children with brain injuries in the first couple of years after birth almost never have the severe language disturbances common to adults with equivalent injuries.
Stage II, of Piaget's stages of cognitive development, the preoperational period
takes place at age 2 to 6 years. Children gain the ability to form mental representations of things in their world and to represent those things in words and drawings.
Object reversal learning
task is to learn that one object always conceals a food reward, whereas another object never does. After the animal learns this pattern, the reward contingencies are reversed so that the particular object that has always been rewarded is now never rewarded, and the formerly unrewarded object now conceals the reward. When the animal learns this new pattern, the contingencies are reversed again, and so on for five reversals.
Stage III of Piaget's stages of cognitive development, period of concrete operations
typically 7 to 11 years. Children learn to mentally manipulate ideas about material (concrete) things such as volumes of liquid, dimensions of objects, and arithmetic problems.
