PSY362 Cognitive Neuroscience Everything for Midterm #2 Marinković Fall 2020 (complete)

hemodynamic (blood flow) imaging techniques (is a hemodynamic neuroimaging method)

- (f)MRI *(functional) magnetic resonance imaging - PET, SPECT *positron emission tomography; single photon emission tomography (gamma rays) *are extremely radioactive, therefore they are no longer used for research *is very important for the field of oncology (screening people for cancer)

are we our faces?

- 40 people in the world have gotten facial transplants

x-ray imaging techniques

- CT *computerized (axial) tomography

EEG method: electrode montage

- EEG electrodes are positioned across the head using the 10-20 EEG montage system *was developed by Herbert Jasper in the 1950's *electrode positions are determined with respect to the nasion (bridge of your nose) and the inion (the bulb sticking out at the very back of your skull [over the occipital lobe]) (distance is measured via the sagittal plane) *electrode positions are determined with respect to the pre-auricular point (is located in both ears [so measure on for each ear]) (distance is measured via the coronal plane) --> electrodes are distributed proportionally to the patient's head size - EEG signals are found by subtracting the reference electrode by the active electrode (active - reference) = active - reference -> this equation is done to eliminate the noise common to active and reference electrodes *full equation: (active - ground) - (reference - ground) *the active electrode is placed near the active area of interest (is best placed over the area of the brain that is probably engaged) *the reference electrode is placed far from the area of interest (examples: the nose, mastoid bones, etc) *it is important to have low impedance ("impedance" means "resistance") (this statement means that the skin must be scrubbed to reduce resistance) *must be at <5 kOhms

why do we bother with EEG

- EEG is used clinically to: i. monitor alertness, coma, and depth of anesthesia ii. test cognitive engagement (via alpha, theta) iii. create biofeedback signal (for anxiety/ relaxation) iv. monitor sleep stages and diagnose sleep disorders v. diagnose epilepsy/ seizures vi. test drug effects

EEG artifacts: eyeblinks

- EEG signals are highly susceptible to being disrupted by artifacts (something that interrupts an EEG signal) *the most common type of EEG artifacts are eyeblinks --> eyeblinks occur as being much larger than the EEG signal (100x larger) -> eyeblinks are disruptive because are cornea is positively charged, and our retina is negatively charged; our eyes are literal dipoles - lateral eye movement also heavily disrupts EEGs (actually moves the EEG signal from left to right, depending on how you move your eye!)

electrobiological imaging techniques (is an electromagnetic neuroimaging method)

- EKG or ECG *electrocardiography (heart) - EMG *electromyography (muscle) - EGG *electrogastrography (stomach) - EOG *electrooculography (eye) - and EEG

electroenchephalography (EEG) origins

- Richard Caton (English physician) *was the first to begin measuring electrical currents in the brains of animals (1875) - Hans Berger (German psychiatrist) *invented the EEG *was the first to measure EEG from a human scalp (1924, published 1929) *discovered Alpha waves ("waves of the first order") *correctly surmised that the EEG is generated in the cortex

cortical visual areas

- V1 is responsible for low level, basic vision *are edge detectors that encode angles of orientation - V2 (also known as the "prestriate cortex" or the "secondary visual cortex") *responsible for processing different combinations -> examples: junctions (a place where two points meet), textures, illusory contours (shapes), etc - V3 *has two subdivisions: i. dorsal V3 -> responsible for global motion (recognizing interesting locations) ii. ventral V3 (also known as "VP" or "ventral posterior") -> helps with orientation (knowing WHERE you are relative to your surroundings), depth perception, and form of objects - V4 *a part of the ventral stream *responsible for color perception, and helps with object orientation - V5 (also known as "MT" of "middle temporal") *is part of the dorsal stream *recognizes motion - these areas are very INTERCONNECTED (meaning that these areas have a lot of feedforward and feedback going on between them)

Are you your face?

- We are not our faces *if we somehow lost our face to injury, we would still be us - we are our brains, and furthermore we are the neurons in our brain that are constantly firing

membrane polarization

- affects resting (membrane) potentials (in the postsynaptic neuronal cell) (-70mV or "-70 million volts") (or "it has an external positive potential) - inside the membrane is mostly negatively charged ions (has larger negative potential) *is made up of mostly K^+ and negatively charged anions - outside the membrane is mostly positively charged ions (has larger positive potential) *most of the electricity comes from here *is made up of mostly Na^+ and Cl^- ions - is the result of the separation of charges inside vs. outside the cell that are spread in thin layers on each side of the cell membrane (a lipid bilayer that separates the inside of the cell from the outside of the neuronal cell) *membrane channels (think of them as gates to the inside/ outside of the cell membrane) line each neuronal cell membrane -> membrane channels open to let various ions in and out -> there is a greater outflow of K^+ down its concentration gradient (outward) (this is opposed by the electrical gradient) (most channels are sodium channels) - the ions that surround the cell membrane like to equilibrate (move from the area of high to low concentration) (sodium [Na^+] usually likes to come in and potassium [K^+] usually likes to come out of the cell membrane) *resting membrane polarization is re-established via sodium-potassium pumps - sometimes passive diffusion occurs (leakage of K^+) - electrical signaling is very fast and brief changes in the resting potential of the resting membrane potential that is caused by currents across the cell membrane - kidney failures are usually caused by neuronal cells in the kidneys being unable to process potassium (K^+); their potassium ion levels go up too much, causes death - lethal injections contain all sorts of sedatives, but what causes death is the potassium, injecting potassium into the bloodstream is fatal because it overloads neuronal cells causing death (it usually reaches the heart first, stopping it)

visual projection pathways other than the retino-geniculo-calcarine pathway

- approximately 90% of the fibers from the optic nerve end up in the LGN - the other 10% ends up in: i. the superior colliculus (in the midbrain) *responsible for eye-movements -> example: you see something and your eye saccades towards it ii. pretectum (in the midbrain) *responsible for pupillary reflex (when pupils constrict or dilate) iii. suprachiasmatic nucleus (in the hypothalamus) *responsible for light/ dark cycle -> example: the visual part of the brain needs to know whether it is night or day

faces

- are unique *despite being just another part of the body (like the hands or feet), they convey so much more meaning (like gender, emotion, age, communication, social attraction, facial expressions, etc) -> is true for Humans as well as many other animal species (like sheep and goats) - is an evolutionary development - are essential for self-recognition *many animals (including humans) recognize themselves in the mirror when participating in the mirror-test (1970) -> the mirror-test is when researchers put a smudge on the animal's nose/ somewhere on their face, then the animal (if it knows it's themself) will try and wipe the smudge off of their face; this is how we can tell if an animal knows it exists/ can recognize itself *Humans do not pass this test until they are around 18 months *75% of chimps, dolphins, killer-whales, elephants, magpies, and gorillas are capable of passing this test

neurotoxins

- cannot cross the blood-brain barrier but block the neural transmission in the body

membrane depolarization (synaptic transmission) (neural signaling)

- caused by excitatory neurotransmitters (like glutamate) binding to the postsynaptic receptor i. chloride channels open --> causes an Na^+ influx into the membrane ii. turns the -70mV resting potential more positive (less negative) iii. the cell becomes depolarized --> causes excitatory postsynaptic potential(s) (EPSP) iv. makes the cell MORE likely to fire v. if the cell fires, it is more likely to cause other cells around it to also fire vi. after some time, the sodium-potassium pump helps restore the neuron to it's resting potential

membrane hyperpolarization (synaptic transmission) (neural signaling)

- caused by inhibitory neurotransmitters (like GABA) binding to the postsynaptic receptor i. chloride channels open --> causes an Cl^- influx into the membrane ii. turns the -70mV resting potential more negative (less positive) *even a small change of a neuron's mV is enough for a neuron to fire more (-40 - -55mV is enough); needs to be as little as ~15mV of positive change iii. the cell becomes hyperpolarized--> causes inhibitory postsynaptic potential(s) (IPSP) iv. makes the cell LESS likely to fire v. after some time, the sodium-potassium pump helps restore the neuron to it's resting potential

action potentials (neural signaling)

- caused by synaptic transmission; is generated at the axon hillock *needs to be as little as ~15mV of positive change in the neuron (caused by EPSP summation) --> this depolarization causes the neuron to fire an action potential - is self-propagating - uses voltage-gated channels down the Nodes of Ranvier to travel - travels across the neuron extremely fast (takes 1-2 ms [milliseconds] to reach destination)

how EEG is generated: PYRAMIDAL CELLS are key players

- contains extensive axon collaterals (axons sends electrical impulses out of the cell by docking their axons close to being into the dendritic spines of other pyramidal cells) *contains regular axons and recurrent axons (recurrent axons are self-excitatory) - are glutamatergic neurons (excitatory output) (this means that when these cells fire, they excite other cells down the line) - are the most abundant type of cell in the cortex (70-80%) - are the only projection neurons (the only outward pathway from the cerebral cortex) - contain both apical and basal dendrites *the apical dendrites contain all sorts of dendritic spines (they look like thorny rose bushes); the majority of synaptic contacts take place here because each individual neurons can have anywhere from 10,000-30,000 connections *the dendrites are very long because these neurons need a very large surface area in order to be connected to so many other neurons *are essential for neural plasticity (they are constantly changing, and are the reason why we are capable of learning and having memory); when something new is learned, new connections within dendritic spines are made *Humans have the most amount of dendritic spines than any other animal we know of (including primates); this is why we are fantastic learners - send info outside of the cortex - is generated in the grey matter of the brain, and then travels through the white matter

neuronal tuning

- developed by Hubel and Wiesel (1959) *won Nobel prize in 1981 - the hypothesized property of brain cells by which they selectively represent a particular type of sensory, association, motor, or cognitive information. Some neuronal responses have been hypothesized to be optimally tuned to specific patterns through experience.

membranes (meninges)

- dura mater is the thick membrane at the very top - arachnoid mater is the spider web looking matter in between the dura and the pia - pia mater is the very, very thin membrane on the surface of the brain; is below the dura and the arachnoid

EEG artifacts: muscle activity

- example: chewing - is 45-50 Hz high frequency activity - pic is on phone; looks like a bunch of really long and wide scribbles

facial recognition is dramatically impaired by

- facial recognition is dramatically impaired by: i. contrast polarity inversion *example: turning a face into all black, blue, and white; and we will have significant trouble recognizing it ii. orientation inversion (having faces upside down) *hurts facial recognition more than object recognition -> example: people will have more trouble recognizing Ryan Reynolds face upside down, than recognizing a car that is upside down - all of this supports the idea that faes are processed holisitically

facial recognition is resilient to

- facial recognition is resilient to: i. image degradation *Humans can handle (recognize faces/ objects) degradation (blurry images at low resolution); computers cannot ii. proportion distortions (compression) *configural relationships can be independent of height and width -> example: a face can be severely compressed (more than 25% width), but Humans would still be able to recognize it; computers cannot - top-down processing is why Humans can do this

filtering EEG signals

- filters are used to clean up artifacts for EEG signals *suppresses undesired noise *named in terms of what they pass, and not what they block

curare (a neurotoxin)

- functions like cobratoxin - used very frequently by native american tribes in South America - is a neural poison that blocks the nicotinic acetylcholine receptor at the neuromuscular junction *results in muscle paralysis (can effect the limbs, lungs, etc) ---> kills people via asphyxiation (suffocation)

cobratoxin (a neurotoxin)

- functions like curare - is a neural poison that blocks the nicotinic acetylcholine receptor at the neuromuscular junction *results in muscle paralysis (can affect the limbs, lungs, etc) ---> kills people via asphyxiation (suffocation)

dipolar current flow (neural signaling)

- has nothing to do with action potentials; this is just a way for EEGs and MEGs to measure brain waves via postsynaptic potentials *measures the extracellular postsynaptic currents of pyramidal cells -> are aligned in a palisade formation (are ~100,000 pyramidal cells per mm^2 of the cortex) -> have a synchronized input -> measures the summation of the postsynaptic potentials of these cells *these ionic (electric) currents flow from the areas of the neurons with positive charge to the area with negative charge *requires hundreds of thousands (or even millions) of neurons to begin to measure brain currents *both the negative and the positive parts of the current (the dipole) are needed to created the current - "sink" and "source" are the poles that form the dipole - brainwaves are currents (like waves) - the "CURRENT SINK" (negatively charged) (think of it like a sink in a kitchen) provides excitatory input to the dendrite *allows positively charged ions (Na^+) to flow into the cell from the current source (positively charged) *this causes a negative external potential on the outside of the neuron *this is our EEG neuronal currents (brain currents) - the "CURRENT SOURCE" (area of positive voltage [positively charged]) provides positive ions to form a return current to complete the loop *provides a passive source of positive ions *can also provide a source of negative ions (Cl^-) - extracellular postsynaptic currents are generated by summated postsynaptic potentials from apical dendrites of highly synchronized, numerous neocortical pyramidal cells - is measured as voltage (the measure of potential energy generated by separate charges) on the scalp (voltage is a relative measure [there is no EEG at a single location]) *EEG can be positive or negative depending on the orientation (location) of the combined dipoles *the EEG current flows freely through the brain, skull, scalp, and tissue (volume conduction) *the EEG recorded on the scalp is positive or negative depending on the orientation of the diploes

visual inferences (perception)

- inference = assumption - many aspects of the world are not directly provided by sensory input *there are no sensors that measure motion, shape, nor object identity - the brain combines sensory input with prior knowledge/ expectations to create the optical illusions that we see as motion, shape, and object identity - visual inferences shape our perception of the world - akintopisa is a condition in which the person experiences motion-blindness *example: a person has a trouble pouring coffee into a cup because they cannot see the motion of the coffee going into the cup, nor how much the cup is being filled

prosopagnosia

- is ONLY an impairment in recognizing face ("face blindness"), they can see objects (like a car/ a table/ etc) just fine - is a form of visual agnosia - is a Greek word: *"prosopon" means "face" *"agnosia" means "lack of knowledge" - little red riding hood has prosopagnosia - is a type of delusional misidentification syndrome - double dissociations between Human and animal facial recognition: A). prosopagnosic with Human faces, can recognize animal faces just fine B). prosopagnosic with animal faces, can recognize Human faces just fine - two types of prosopagnosia: i. acquired prosopagnosia *caused by bilateral or right-sided lesions of the inferotemporal area (the fusiform gyrus), usually caused by infarcts/ hemorrhages of the posterior cerebral artery *usually occurs suddenly ii. congenital prosopagnosia *no known head trauma, but is genetically acquired *usually pretty high-functioning *some people recognize every face that they have ever met (not prosopagnosia); Prof thought it was interesting - prosopagnosics can recognize faces when they are inverted

agnosia

- is a Greek word: * "a" meaning "without" *"gnosia" meaning "knowledge" - is the "absence of knowledge" or "a loss of ability to recognize objects, persons, etc. in a certain sensory modality - ~26 types of agnosias

visual agnosia

- is the inability to recognize familiar objects and faces in the context of preserved visual functions ad preserved recognition by other senses (touch, sound, etc) - there is nothing wrong with the visual system, the problem is with the identity recognition system - there are many types of visual agnosia, two major types include: 1. prosopagnosia (inability to recognize faces) 2. alexia (inability to recognize text, despite being still having the ability to write) - usually caused by lesions in the brain *because lesions usually affect large areas of the brain, a person usually has more than one type of agnosias ("pure forms are very rare")

FAST

- is the method used to detect strokes: Face *if face is droopy, or looks funs; this could be a stroke Arms *if the person is having trouble controlling their arms; this could be a stroke Speech *if the person's speech is slurred/ they are having trouble understanding you; this could be a stroke Time *time is critical! if any of these symptoms are seen, 911 must be called immediately! - the person may also lose balance, and/or having vision problems

visual fields

- is what you see in front of you - each eye gets information from both visual hemifields *both fields areseen by both eyes overlap (if confused look at the picture on right) i. the right temporal retina receives information from the left hemifield ii. the right nasal retina receives information from the visual world iii. the left nasal retina sees the left hemifield iv. the left temporal retina sees the right hemifield *some areas of vision are seen only by the left eye or the right eye - Humans use binocular vision *vision in the center field is binocular *vision in the periphery fields is monocular (the most medial [middle/inside] portions of the nasal retinas)

cortical circuity

- lower part of the cortex is crammed with cell bodies and dendrites - upper part of the cortex consists of axonal connectivity via massive dendritic trees ("dendrite" means "tree" in Greek) and branches that trade all sorts of connections

neural circuitry

- mainly composed of pyramidal cells and interneurons (commonly inhibitory) - 2/3 of the energy the brain utilizes is used to fire neurons (in order to facilitate our bodily functions, thoughts, and actions) *the energy (as ATP) goes to the sodium-potassium pumps in order; is a necessity for firing neurons - 1/3 of the energy the brain utilizes is used for cell maintenance - the capillaries in the brain and the neurons are so interdigitated (intermixed) that there is roughly one capillary per neuron in the brain (each capillary is not assigned to each neuron, but there the point is that there are so many in the brain) - a single presynaptic potential is slow, therefore action potentials occur when summated potentials reach the firing threshold (see graded potential card below) at the axon hillock (the trigger zone), and then an action potential is triggered

transient ischemic attack (TIA)

- may occur before a full blown stroke - also known as "mini strokes" or "transient mini strokes" *because (like strokes), they have a short duration and sudden onset - is when a blood clot temporarily blocks blood flow *usually goes away on its own - are very important for detecting strokes down the line; if you have one of these, a stroke may very likely and shortly be imminent - symptoms: include tingling/ numbness; and weakness on one side of the body; transient vision problems (can feel like there is a "dark curtain in front of your eyes")

EEG method: electrode application

- multiple EEG electrodes are applied to the scalp *with washable gel and creams *with collodion for a longer-term solution -> collodion is adhesive, it stays attached, it makes it possible to monitor patients for days (works kind of like glue (example: is essential for epilepsy monitoring[when a patient may toss and turn for days because of their neurological condition]) *good contact with the skin is essential - modern technology has produced (this will eventually be widespread within the next 30 years) electrocaps *quick and easy application *positioned (in a similar way to EEG electrodes) onto and across the patient's scalp for an equal distribution of data across the head *on the inside, is filled with plastic rings around metal electrodes that form electrode wells that are filled with gel

How is EEG measured?

- multiple EEG electrodes are needed on the skull in order to measure the summated postsynaptic potentials (EPSPs and IPSPs) that create dipole currents *why? because EEG activity is not recorded directly above summating postsynaptic, but rather it is recording the dipole currents created by them; therefore, EEG activity is not localized, but rather occurs all throughout the head --> this is allowed to occur via conductivity barriers throughout the head (different tissue types); CSF (cerebrospinal fluid) is extremely EEG conductive and it is abundant all throughout the brain, therefore once the dipole reaches the CSF, it is able to travel all throughout the brain (is affected by differences of conductivity among different tissue types) -> the skull is about 70x worse a conductor than the brain (which is also a poor conductor); this is why CSF spreads the electrical dipole currents throughout the brain (because dipole currents travel along the path of least resistance [CSF]) --> dipole current flows have a wide distribution along the scalp (is all over the head), but very poor spatial resolution (the source of the brain that generated the EEG signal cannot be localized to exactly one location [we cannot tell where the signal was generated]) -> a fraction of activity can be detected - EEGs on the skull are measured in micro Volts

atherosclerosis

- narrowing of the arteries that reduces blood flow due to a buildup of fatty deposits (plaques) (cholesterol); these plaques can break off and cause all sorts of trouble in other areas of the body - common at the bifurcation of arteries (very common in the carotid artery)

how do we perceive visual objects?

- neural pathways support increased stimulus complexity via functional localization - the visual system makes relative comparisons rather than absolute judgements for: i. brightness ii. color iii. size *this causes all sorts of errors - perception is reconstructive and creative (top-down) *perception is not always realistic; we do not see reality for what it is, we construct our reality around us (includes memory) -> the brain's goal is to ultimately construct a coherent view of the world, telling you what it thinks you should see or hear, it doe snot always accurately report what is really going on

graded potentials (synaptic transmission) (neural signaling)

- neurons have thousands of EPSPs and ISPSs going off, the summation (combined effort) of all of these inputs either results in the neuron firing more, firing the same amount, or being less likely to fire *if the cell is not sufficiently polarized, and the EPSPs do no reach the firing threshold, then nothing happens *several EPSPs going off at the same time in order to reach the threshold to fire is called "SPATIAL SUMMATION" (summing potential from different locations) *several ESPS going off back to back (not at the same time, but close) in order to reach the firing threshold is called "TEMPORAL SUMMATION" (summing potentials across time) - action potentials occur when summated potentials reach firing threshold at the axon hillock (the trigger zone), and then an action potential is triggered

hemifield

- one half of your visual field - divided by your nose

top-down processing

- our actual perception of the world is severely altered by our unique beliefs, experiences, expectations, and goals *our personalities cause us to unconsciously, selectively interpret sensory information to fit a framework that makes sense to us - visually needs instructions when solving problems - uses contextual influence *the word superiority effect -> is the better recognition of letters embedded in words compared to isolated letters or those in nonword letter strings -> example: what is the middle letter? i. t4e ii. c4t is the middle letter "h" or "a"? the answer is that it is both; top-down processing is what allows us to use our personal context to make sense of the world around us, for this reason it is more important to us than sensory (bottom-up) processing

optical ilusions

- our perception of the world is actually very different than actual reality *we create internal representations of the external world (called "the brain matrix") - all knowledge is derived from the brain, not independent of it - example: picture on the right doesn't exist, our brain fills in the spaces to make a cube, even though the picture doesn't actually form a cube

object agnosia

- patient CK could not see objects, only faces (very, very rare); they also were impaired when reading words, and could not recognize inverted faces

associative agnosia

- patients can describe/draw/copy objects, but not recognize them *these people cannot assign meaning to objects and/or faces and/or words *example: if you showed one of these people a key, they could describe the key to you (it is round, with a sharp, straight edge, etc), but would not know what it is; however if you put it into their hand, they would then recognize it from another perceptual input and would be able to tell you what it is - are commonly caused by bilateral (often left-dominant) lesions in the areas of the posterior cerebral artery (the ventral visual stream area)

bottom-up processing

- proceeds along the visual pathway (LGN --> V1 --> V2, etc.) - also called the "feedforward stream" - driven by sensory info from the physical world - visually stands-out when solving problems

thatcher illusion

- q phenomenon in which people have difficulty noticing local feature changes (e.g., upside down eyes or mouth) in an upside down face; but when it's right side up, it just looks grotesque - examines second-order processing

neurophsycology (lesion studies)

- really relies on lesion studies *studying people with brain damage (lesions) to measure where their brain is damaged, and how it affects them (what impairments they have), and then generalizing their findings to the general population - this field has laid the empirical foundation for modern cognitive neuroscience - examines how functional impairments are related to brain lesions - these methods allow researchers to test hypotheses about: i. the localization of brain functions (the idea that certain brain areas are responsible for certain functions) -> keep in mind that the brain is highly compensatory; do not assume that everything is localized ii. parsing cognitive functions into subcomponents (modularity) iii. reveals brain areas that are NECESSARY for a task

how EEG is generated: NEURONAL SIGNALING

- recorded as EEG - neuronal signaling is an electrochemical process *cells with axons will loosely connect to other cells dendrites in order to communicate with each other; this occurs via: i. electrical process: a. when a presynaptic cell neuron (the sending cell) generates an action potential, it sends it across it's axon to the other cells dendrite b. at the juncture where the axon meets the other cell's dendrite, there is a junction called a "synapse" between the two neuronal cells (a small space separating them) ii. chemical process: a. at the synapse between the two neuronal cells, the cell body's action potential commands the axon to release neurotransmitters b. the neurotransmitters from the presynaptic cell cross the synapse and cause changes in the resting potential of the postsynaptic neuron (the receiving cell) c. the resting potential is converted into postsynaptic currents, which changes the electrical status of the postsynaptic neuronal cell, telling it what it has to do; it now has it's orders

stroke

- suffocates brain tissue (from lack of blood flow); causes massive neuronal death; if the person survives, the brain gets rid of all the dead brain tissue and CSF (cerebrospinal fluid) then fills the cavity - ~85% of stokes are ischemic (infarction [obstruction]); two types: i. thrombotic (a blood clot builds up in response to a buildup of fatty deposits) * is 60-70% of all ischemic strokes ii. embolic (when an embolus [a plaque, or clot, or fat globule] travels from elsewhere in the body) *is 30-40% of all ischemic strokes *is similar to how comrade Michael Brooks died :/ --> ischemic strokes can be treated via a very quick injection of a tissue plasminogen activator (TPA); these are used to dissolve clots, and can treat both thrombotic and embolic strokes - ~15% of strokes are hermorrhagic (rupture of an artery); two types: i. intracerebral (within the brain) *these types of strokes are less common (~10% of all hemorrhagic strokes) *with these types of strokes, not only is the lack of oxygen damaging, but blood irritates neural tissue; these type of strokes BAD, and often very lethal *usually occurs because an aneurysm (a weakness in the arterial wall; this weakness balloons); if the aneurysm pops, then this is what usually causes the intracerebral hemorrhage *is how Grant Imahara died :/ ii. subarachnoid (blood accumulates between the brain and the skull) *these types of strokes are more common (~90% of hemorrhagic strokes) *usually occur via popped aneurysm in the arachnoid mater between the brain and the skull - most stokes occur within the middle cerebral artery (MCA) in the brain *the MCA supplies 2/3 of the lateral surface of the hemisphere and the temporal pole *if a stroke occurs here, the person is very likely to have issues with primary motor and sensory areas/ face and upper extremities , and language - *IF SOMEBODY BEGINS PUKING AFTER A BRAIN INJURY, TAKE THEM TO THE EMERGENCY DEPARTMENT AT YOUR LOCAL HOSPITAL IMMEDIATELY; THIS IS THE BRAIN GETTING IRRITATED FROM BLOOD FLOWING THROUGHOUT THE BRAIN

EEG measures

- summated postsynaptic potentials (EPSPs and IPSPs) that create dipole currents; caused by action potentials *(electrical activity from the cerebral cortex) *(the difference between the active and reference potentials) - is measured in micro Volts on the scalp

pareidolia

- tendency to perceive meaningful images in meaningless visual stimuli/ random visual patterns *example: seeing faces in the clouds

face composite task

- tests holistic processing by using aligned and misaligned facial recognition tasks *combining two different faces together creates a completely different face

continuous EEG

- the brain "never sleeps" (it is always active) (it is always oscillating) - Alpha oscillations (waves): 8 - 10Hz (Hz = oscillations per second); a Hz on the picture shows up as a bump *largest alpha oscillations are during wakeful rest when the eyes are closed (in bed but not asleep) *decrease by opening the eyes *most prominent posteriorly

concentration gradient

- the difference in the number (the concentration) of ions found outside vs. inside of the cell membrane

blood-brain barrier

- the first layer is a series of tight junctions composed of endothelial cells (linings of the capillaries) in which only small molecules (like water) or lipid-soluble molecules (like alcohol, barbiturates) can pass - the second layer are walls of astrocytes (specialized glial cells) which help transfer metabolites from the blood to the neurons, remove waste, excess neurotransmitters, etc - protects the brain from "flotsam/jetsam" (junk/debree) in the bloodstream - is essential to maintain a constant internal brain environment

How do we perceive visual processing?

- the further down the visual pathway, the more complex the visuals are brain will be able to comprehend *example: V2 alone can process basic shapes (like a triangle/ a target), but V2 and V4 (which is further down the ventral stream) together can process more complex pictures (like a bed, or the sun)

inhibitory neurotransmitter

- the most common inhibitory (polarizing) neurotransmitter in the brain is by far GABA *20-30% of neurons in the brain are interneurons that primarily use GABA

synapse chemical process

- the synapse is the small (30-40 nanometers) junction where the axonal boutons (knobs) of the presynaptic neurons meets the dendrite of the postsynaptic bouton * there are multiple synapses per neuron (1 billion per mm^3) - process: 1. the action potential reaches the very end of the terminal of the axon bouton of the presynaptic neuronal cell 2. the neurotransmitter calcium channels in the terminal bouton of the presynaptic neuron open up 3. the Ca^2+ (calcium) ions on the outside of the vesicles' cell membranes release neurotransmitters 4. the neurotransmitters cross (float across) the synapse to the postsynaptic neuronal cell 5. the neurotransmitters bind to neuroreceptors on the dendritic spine of the postsynaptic neuron 6. the binded neurotransmitters signal goes to the specific membrane (ion) channel that will let it inside the cell membrane of the postsynaptic neuron (opens the membrane channel up), then it changes the resting membrane potential, telling the postsynaptic neuron what to do 7. neurotransmitter effects are then terminated via: i. degradation by enzymes -> enzymes that degrade/ dissolve neurotransmitters ii. reuptake -> the presynaptic cell takes the neurotransmitter back to reuse it later -> SSRIs (used to treat depression) inhibit serotonin reuptake iii. diffusion away from the synapse -> the leftover neurotransmitters just float away from the synapse

organization of cortical visual areas

- there are currently a more than 40 - most connections are reciprocal (information is shared back and forth between the areas) - everything is basically connected to everything else (MASSIVE INTERCONNECTIVITY) *there are 305 connections (31% - 40% of all possible pathways within the brain) - the LGN only gets about 5-10% of its input from the retinas; 90-95% come from: a. the visual cortex b. superior colliculus c. pretectum d. raphe nucleus (seratonin) e. locus coeruleus (noradrenaline) f. etc/ more areas - only 5% of input to V1 comes from the LGN and the retina! *the rest of the 95% is coming in from all over the rest of the brain including: a. V2 b. V3 c. V4 d. V5 (MT) e. frontal eye fields (FEF) f. lateral intraparietal (LIP) g. inferotemporal cortex h. etc/ more areas

functional visual pathways (steams)

- there is no center for vision in the brain *there are two major visual streams: i. the perceptual stream (also called "the ventral stream" WHAT) -> starts in V1 and then move through and into the ventricular part of the temporal cortex -> identifies objects -> responsible for "WHAT is that thing?"; is vision for perception and identity -> responsible for recognizing shapes, sizes, objects, faces, text -> is used for visual recognition, memory, and emotional context -> includes the fusiform cortex ii. the action stream (also called "the dorsal stream" WHERE) -> starts in V1 and then moves through and into the dorsal part of the parietal cortex -> guides action in real-time -> responsible for "where is something?" and "how to do something?"; it provides vision for action -> is sensitive to location, distance, relative position, motion -> is relevant for the guidance of actions (example: reaching across a table for a cup of coffee) -> feeds information into the motor cortex - these streams together integrate our perception of the world (they work together) (called "the patchwork-type model") *example: if something is flying towards you from a distance, your brain needs both of these streams to be able to recognize the object and then either dodge it or catch it

neuroimaging methods

- two major methods: i. electromagnetic methods *excellent temporal resolution (can see what is being measured millisecond by millisecond) *directly reflect neuronal activity *excellent for viewing neural activity ii. hemodynamic methods *excellent spatial resolution (where things are happening in the brain when measuring something) *indirectly reflect neuronal activity *detects blood flow *is horrible with detecting when something is occurring (because it detects blood flow, there is a horrible time-lag between the bodily event and the effects of the bodily event that hemodynamic methods pick up) -> example: if the vascular system has a rupture, hemodynamic imaging methods might take 5 seconds to discover this rupture

visual object processing

- visual object = any visual stimulus *example: could be a face, or a car, or a salad, etc 1. people first notice the first-order configural processing (category level): *people discern whether what they are looking at is a face vs. another visual object (faces vs. cars) 2. then people notice second-order level relational processing properties: *people discern within-category differences/ the differences between configurations -> example: is it Joe or Peter? - people process stimuli "holistically" (meaning that people fuse features into a gestalt representation; when recognizing faces, people do not just look at the eyes, or the nose, or the mouth, but rather they look at the whole face when recognizing) *we focus on emergent features (parts qualitatively [qualities] that are unique/ different from the sum of their parts) -> example: we might be more likely to recognize somebody by the fact that they have a more unique nose than most other people - people are horrible at part-based face processing alone, without holisitic/configural face processing *example: we might not recognize Larry's nose alone, unless it is attached to the rest of Larry's face --> people remember faces better when the unique parts of those faces are embedded into the face rather than when isolated from the rest of that face *example: people might not have a problem recognizing the door to Larry's house, even if it is isolated from the rest of Larry's house --> people tend to not have difficulty remembering objects that are separated from the rest of the object; this problem only applies to faces

excitatory neurotransmitters

1- glutamate (the most excitatory [depolarizing] neurotransmitter by far) *70-80% of neurons in the brain are glutamatergic neurons (they use primarily glutamate) - very few neurons in the brain use these neurotransmitters; they are primarily modulators: i. acetylcholine ii. dopamine iii. norepinephrine

membrane polarization nomenclature

1. Na^+ *is Latin for "natrium" *is English and French for "sodium" *is Arabic for "suda" (means "headache" in Arabic) *was historically known as a way to alleviate headaches (via sodium carbonate ingestion) *is the 6th most abundant element 2. K^+ *is Latin for "kalium" *is English for "potassium" (comes from "potash" as it was originally isolated from the ashes of plants) *is Arabic for "quali" *is the 7th most abundant element

retino-geniculo-calcarine pathway (the primary visual pathway)

1. light hits the retina (retino) 2. the light excites the photoreceptors (retino) 3. - the information is inverted from top to bottom and left to right (retino) *this is an ancient contralateral organization that has been in widespread use by vertebrates for hundreds of millions if not billions of years -> examples: i. the right visual field is processed in the left visual cortex ii. the left visual field is processed in the right visual cortex *retinal fibers from the nasal retina cross over at the optic chiasm *the information from the temporal retinas projected to their own sides of the brain (they are already on opposite sides) *the information from the nasal retinas is projected to the opposite sides of the brain (they are not on opposite sides, and so must be projected as such) 4. ganglion cells are activated; send information to their axons (retino) 5. ganglion axons send information to the lateral geniculate nucleus (LGN) in the thalamus (retino to geniculo) *approximately 90% of the fibers from the optic nerve end up in the LGN *if this is severed, then the person becomes blind (even if everything else including the eyes and occipital lobe are intact) 5. the LGN relays that information to area V1 (the striate cortex) in the calcarine fissure within the occipital lobe (geniculo to calcarine) *area V1 has retinotopic maps that process the contralateral visual information it receives -> is a 2D topographic map of the image of the retina -> the visual information is distorted, and not what your eyes actually see; this is because people prefer to focus on the center of their visual field (what is directly in front of them; if the stimulus isn't directly in front of them, people tend to move their heads in the general direction of the stimulus of interest); this leads to much larger representation of the foveal area in vision coming from area V1 (called "Cortical Magnification"); this is why people have poor peripheral acuity *the fovea occupies approximately 50% of V1 vision 6. conscious viusal analysis occurs!

Why is EEG generated by postsynaptic currents and not action potentials?

Because pyramidal cell bodies and dendrites are slow enough that they tend to synchronize with each other, this creates the flow that EEGs pick up; whereas action potentials and the axons that generate them are going off too fast for their to be any widespread synchronicity

cortical organization of Macaque monkey vs. Human

Macaque: i. visual cortex: 52% of the cortex ii. somatosensory cortex: 10% of the cortex iii. auditory cortex: 3% of the cortex iv. motor cortex: 8% of the cortex Human: i. visual cortex: 27% of the cortex ii. somatosenory cortex: 7% of the cortex iii. auditory cortex: 8% of the cortex iv. motor cortex: 7% of the cortex v. cognition, emotion, and language: 51% of the cortex

resting state extra fact

at the resting state, a higher concentration of Na^+ is found outside a neuron and a higher concentration of K^+ is found inside a neuron

cortical microenvironment contains

i. capillaries ii. pyramidal cells iii interneurons

common types of lesions in humans

i. traumatic brain injury (TBI) *several intersectional types: a. open head injury (when the skull has been opened) b. closed head injury (the skull is intact) c. focal lesions (lesion that is only in a particular part of the brain) d. diffused lesions (damage to the connecting fibers throughout the brain) -> helmets are essential to preventing these because helmets can break and absorb the energy transferal process that usually damages the connecting fibers of the brain upon impact) e. swelling -> can cause internal bleeding and pressure ii. tumors *any tumor can cause increased intracranial pressure iii. degenerative diseases *example: Parkinson's disease iv. strokes (also known as CVA or "cerebral vascular accident) *is a rapid onset of symptoms v. cerebrovascular disease *is the most common type of neurologic disability in Western countries *is the number 3 most common cause of death (after heart attacks and cancer)

interneurons

modulates pyramidal cells (keep them in check)

EEG is made possible by

pyramidal cells aligned parallel in the cortex

What characteristic of pyramidal cells allows for postsynaptic currents to summate so that they can be recorded as EEG in the cortex?

they are aligned