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Psych 1XX3 - Exam Notes (Lectures from Entire Year)

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Department
Psychology
Course
PSYCH 1XX3
Professor
Joe Kim
Semester
Winter

Description
Development 1 – Module Levels of analysis and how they shape the sensory systems and behaviour: Development – refers to the changes and continuities that occur within the individual between conception and death; how you change and stay the same over time Maturation – biologically timed unfolding of changes within the individual according to that individual’s genetic plan; specific environment conditions shape the genetically determined plan; ie – grow tooth at 5 months Learning – the acquisition of neuronal representations of new information; relatively permanent changes in our thoughts, behaviours, and feelings as a result of our experiences. Learning processes allow you to acquire new information and respond to events ie –don’t touch the hot stove, look before crossing the street etc. Some of these become automatic but this can cause trouble in new environments, ie – in Europe you have to look right then left instead of left than right to cross the street like in North America Interactionist Perspective – the view that holds that maturation and learning interact during development You can’t learn to walk until you’ve developed muscles/are able to balance, you can’t talk without proper mouth dexterity (maturation affects learning) Child given food/water but left in a dark room will have bad vision and slurred speech (learning affects maturation) How do we tell if infants like something? Habituation – repeated exposure to the same stimulus (tone, colour, object) while measuring physiological responses (heart rate, breathing, eye movements) until everything becomes baseline (habituated); a decrease in the responsiveness to a stimulus following it’s repeated presentation Dishabituation – an increase in the responsiveness to a stimulus that is somehow different from the habituated stimulus; ability to recognize new stimulus from the old one but if the reactions are the same then they don’t know it’s a new stimulus High amplitude sucking method – measure baseline sucking rate for infant in the absence of a stimulus. Then, present music notes and if the infant sucks faster on the pacifier the music notes continue to be presented but if the infant sucks slower on the pacifier the music will end. Preference method – infant placed in looking chamber to simultaneously look at two different stimuli and measure which they look at more for which they like better Inferences/Assumptions with these methods – not always accurate for example if you put a ghost stimulus in a haunted house and measure the escape times as the amount of fear a person with a broken leg has a slower escape time but that doesn’t mean they’re not scared of the stimuli The Competence-Performance distinction – an individual may fail a task not because they lack those cognitive abilities but because they are unable to demonstrate those abilities. Ie, a pre-verbal infant can’t talk so it might look like they don’t know what you’re asking but they do, they just can’t communicate it. What are the two ways we developmentally design research? Longitudinal design – a developmental research design in which the same individuals are studied repeatedly over some subset of their lifespan. Ie, perform some test on same person every year to track progress. Pros – you’re using the same people, don’t have to worry about controls. Cons – loss of participants in a study such that the sample ends up being non-responsible of the population as a whole (selective attrition), changes in the participants’ responses due to repeated testing (practice effects), time consuming, expensive Cross-Sectional design – individuals from different age groups are studied at the same point in time. Pros – allows researchers to assess developmental change, relatively less time consuming and expensive; can uncover age differences. Disadvantages – cannot distinguish age effects from generational effects, cannot directly asses individual developmental changes. It is best to combine both tests. Development 2 – Module Zygotes – new cell formed with 46 chromosomes, 23 from each parent Chromosome – threadlike structure made from DNA Genes – chemical code for development, we could each potentially have 64 trillion genetically distinct offspring Autosomes – 22 chromosomes that are the same between men and women Sex chromosomes – 23 chromosome, XX (women), XY (men), gender is determined by father Genotype – inherited genes (BB, Bb, bb) Phenotype – expression of the genotype into observable characteristics (brown hair, blue eyes etc) Phenotypic expression is the outcome of many genetic factors that is often more complex that one pair of genes. Simple dominant-recessive inheritance – pattern of inheritance in which the expression of a trait is determine by a single pair of alleles Homozygous – when two alleles have the same effect on a phenotype (BB or bb) Heterozygous – when two alleles have a different effect on a phenotype (Bb) Dominant allele is expressed in the phenotype and the recessive allele is not expressed but still heritable. Polygenetic inheritance – multiple genes are involved in the expression of a trait, ie – height, weight Codominance – two dominant alleles are both fully and equally expressed to produce a phenotype that is a compromise of the two Sex-linked inheritance – genes expressed on the X chromosome Extreme Behaviourist Point of View – nature was all important, independent of genetics, based on proper environmental control and training Genetic point of view – inherited genes, minimal environmental factors The canalization principle – genotype restricts the phenotype to a small number of possible developmental outcomes. Some developmental processes are buffered against environmental variability. Ex – universal phonemic sensitivity is independent of the environment, all babies babble the same. Range of reaction principle – genotype establishes a range of possible responses to different kinds of life experiences. Example – your potential range of height is determined by genetic factors, but your final height is dependent on your access to nutrition, exercise, and sleep What are the 3 ways that genes influence environmental experiences? Passive Genotype/Environment correlations – the environment that parents choose to raise their children in was influenced by the parents’ own genes. Ex – athletic parents focus on athletic toys, smart parents focus on smart toys • Most influential at childhood Evocative Genotype/Environment correlations – the traits that we have inherited affect how others react to and behave towards us. Ex – if you have a bitchy temper, people won’t like you • Equally influential throughout life Active Genotype/Environment correlations – our genotypes influence the kinds of environments that we seek. Ex – if you have sensation-seeking genes, you’re going to search out adrenaline filled environments • Most influential later in life Intelligence and twins – for monozygotic twins raised together, their intelligence correlation is 0.86, if they were raised apart it is 0.72, for dizygotic twins it is 0.60 Critical Period – window of opportunity within an individual’s development in which particular environmental stimulation is necessary in order to see permanent changes in specific abilities Kitten Experiment • If their vision was deprived from their birth for a period of time, even if they are given visual stimulation after the critical period, no amount could help it regain normal visual activities; permanent damage • If their vision is normal for the first 6 weeks of life, then deprived, it will still be able to discriminate visual patterns when it is given vision again (since it was deprived after the critical period) • These implications in humans could affect parents’ choices to adopt Without normal stimulation, the brain loses some functions. However, brain circuitry is not permanent at any age, it is malleable all through life. Experience-expectant brain growth – our brains have evolved to expect a certain amount of environmental input and with this input our brains develop normally Experience-dependent brain growth – our brains develop according to our own personal experience, ie – calluses o fingers and changes in brain for music will occur if you play guitar all the time Sensitive Periods – brain maintains some capacity for changes and growth in adulthood; our brains develop according to our own personal experiences. Flexibility in the timing and type of stimulation required for normal development. Development – Live Lecture Two common rumours – infertile couples who adopt are more likely to conceive and nurses report the busiest times/greatest number of births on full moons No data supports either of these but selective hearing, confirmation bias, and the fact that we only really hear about the strange stuff cause it’s interesting cause these to become population Common inaccuracies – people only use 10% of their brains, in romantic relationships opposites attract, H2O flows down the drain in opposite directions in the northern and southern hemispheres, babies born with full head of hair caused heartburn in mothers Cello scrotum – the low frequencies somehow affect young boys who play the cello. Original authors revealed it was a hoax, even scientists aren’t immune to fake claims Sex and Gender • Storm – parents withholding the baby’s gender • Is it appropriate to tell the world a gender? • People tend to respond certain ways to girls vs boys • Knowing the sex influences how you cat • Babies in the 1800’s were all dressed in white dresses • Dr. Kim dressed his baby “M” in pink and blue to see how people would act o Pink – gently, rocking, such a pretty baby o Blue – wrestle, more aggressive, what a big boy Sex – XX vs XY Gender – very strong social roles Brenda/David • 1970’s genetically identical boys (twins) but one had his penis destroyed so gender reassignment surgery made him Brenda • Brenda never felt like she fit in • At least a part of what we consider gender roles must be biological • Brenda became David The first 3 years movement – there is explosive brain growth development in this time, more neurons and synapses in babies than adults but they’re not all useful many are pruned away to get rid of the excess connections The Mozart effect – listening to classical music will increase a baby’s intelligence – one group did and one group didn’t listen, the one that did performed better on a cognitive test but the study used undergrads not babies Orienting Reflex – watching a novel stimulus because it catches your attention, not because you’re actually paying attention Most babies should be talking/babbling/socializing not sitting in front of a TV screen Doomsday • Mayan calendar ends on Dec 21/12 – true • Earth, sun, and milky way galaxy are in alignment on this day – true (but happens every year) • The world is going to end – not yet certain Evolution 1 – Module How do adaptations arise? – Activation of relevant genes in interactions with relevant environmental aspects that are maintained through natural selection Darwin and Wallace 4 basic mechanisms of evolution – natural selection, mutation, genetic drift, migration Differential survival and reproduction of organisms as a result of the heritable differences between them 3 essential components to this theory • Individual Differences – variation among individuals for any given characteristic • Differential Reproduction – these differences affect changes of surviving and reproducing • Heritability – offspring of successful reproducers will resemble their parents (have the same traits) Ex – red fish vs blue fish, the blue fish aren’t seen but the red fish are so the red get nommed and the blue survive to pass on their blue colour gene so eventually the population becomes blue Stabilizing selection – selection against any sort of departure from the species-typical adaptive design; ie – blue would keep remain the same because it keeps them reproducing Darwin’s Finches and the Galapagos • Drought occurred – meant only birds with big beaks could crack the bigger seeds left behind, therefore those with big beaks survived and reproduced causing an increase in the average beak size. After the drought since little beaks could survive again the average beak size decreased again • Most observable changes are small but permanent changes can lead to speciation Survival of the fittest – adaptations promote reproductive success which isn’t necessarily the biggest or strongest traits; natural selection favours the reproducers, those who are best at reproducing, not surviving Darwinian fitness – average reproductive success of a genotype relative to alternate genotypes Reproductive fitness – how good a particular genotype is at leaving copies of its genes in the next generation as opposed to other genotypes Evolution – change in gene frequencies over generations Sexual Selection Sexual selection – component of natural selection that acts on traits that influence an organism`s ability to obtain a mate Peacocks – whichever male has the most impressive feathers wins the ladies but lugging that tail around costs them energy and leads them to being eaten by predators more easily therefore they shed the tail at the end of the breeding season and grow a new one Elks – only males have the giant antlers, they find to woo the ladies, but with the giant antlers they can`t run as fast as women to escape prey and so they shed their antlers at the end of breeding season then grow a new one Both the peacock and elks sexual selection traits have negative effects on survival but it evolves and persists because it has a positive effect on the chance to mate. Selective force – what causes mate choice There are two ways to gain more s to mates vs your rivals 1. Being chosen by the opposite sex (peacock) a. This is very intense because female peahens choose very specifically the peacocks with the more spots even if it’s only a few more spots and those that are symmetrical – it’s because they are picking the ones that will give their offspring the best chance of living 2. Defeating your rivals (elk) a. More likely to be resistant to diseases if they are strong, best chance for survival Behaviours are adaptations – some species typical behaviours include physical form, habitat preference, group size, and social system Behaviours can have genetic properties – we breed certain dogs Evolution 2 – Module Effect on actor’s well- being Effect on recipient’s well- + being + Cooperation - Selfishness Good helping gene – does it for the good of the gene, ex – group of birds searching for food means less individually but food is being found and you can take it from other people too Also, in groups, some can search while some scan for predators when you’re alone you have to try and forge and scan at the same time – the greater number of birds, the less each individual looks up but the group as a whole is more careful (looks up more altogether) Altruism – behaviour in which the actor incurs a cost to provide a benefit to a recipient Not altruism – foraging/vigilance in groups; not altruism because the actor gains directly from the behaviour The good of the group cannot explain the evolution of altruism, “altruistic” genes would die off and therefore not be passed on, so how come they still are? Genes for altruism could be successful if they help identical copies of themselves Eusocial Hymenoptera – includes all ants and some bees/wasps; most individuals spend their lives serving the colony without reproducing; everyone in the colony is related it pays to help the colony Direct fitness – fitness from personal reproduction Indirect fitness – fitness from the reproduction of close genetic relatives; you can increase your fitness by helping kin to successfully raise their offspring sometimes even when doing so has a negative effect on your own direct fitness Inclusive fitness = direct fitness + indirect fitness Hamilton’s Rule rB > C The reproductive benefit to the recipients (B) multiplied by the probability that he recipients actually have identical copies of the same gene or coefficient of relatedness (r) must be greater than the reproductive cost to the actor (C) r – Relatedness between individuals B – Benefit to the recipient (probability that recipients have some identical gene) C – Reproductive cost to the performer Parent -> offspring = 0.5, sibling -> sibling = 0.5, first cousin-> first cousin = 0.125 Aggression also decreases as you become more related to the people in your group 25% of homicides are committed by relatives, 6% are committed by ‘genetic’ relatives Cinderella syndrome – rates of child abuse are higher amongst step children than biological children How do we identify kin? Inbreeding with close relatives can decrease fitness through genetic incompatibilities Neighbours – don’t need to know relatedness just help neighbours since you’re more likely to be related due to minimal migration in certain species Belding’s ground squirrels – females stay in the same area for life so they give more warning calls (altruistic) than males who leave Phenotype matching – an evaluation of relatedness between individuals based on an assessment of phenotypic similarity If phenotypic matching in humans influences your actions then you might expect that individuals would exhibit more pro-social behaviours such as trusting and sharing when interacting with others who resemble them Game-playing experiment • Hypothesis – people would be more trusting of individuals who resemble kin • Person either played with a stranger or someone who looked like them • Subjects were more trusting of player 2 when player 2 resembled them • Had to trust player 2 in order to be given more money (player 2 had to be trusted to split the money equally) if they didn’t trust player 2 they could just keep the money but it was less money Direct reciprocity – situations in which individuals help each other and both benefit Indirect reciprocity – individuals help those who have helped others Behaviours that appeal altruistic from the perspective of the individual are actually selfish from the gene’s perspective. Evolution – Live Lecture Gene and family resemblances – people say babies look more like the dad, true or false? Unrelated people usually go 50/50 for looking like mom or dad On the mother’s side of the family people typically say the baby looks like the dad, this is because who really knows who the dad of the baby is right? (Aside from Maury) so the mother’s side of the family has to be like ‘yeah yeah it totally is your baby’ Genetic Cuckoldry – tricking another guy into thinking it’s his baby and having him raise the baby like it’s his Heritable variants lead to differential reproductive success; evolved psychological mechanisms can be described as information processing devices Men and women have to come up with different strategies for fitness: • Different parental investments • Different metabolic demands of reproduction • Women should be picky because they can only reproduce one at a time • Men can impregnate lots of women therefore should be less picky • The longer you know someone the more likely you’ll have sex with them but men get there faster • Deep voice is heritable – testosterone almost exclusively determines voice depth but too much testosterone is not good We don’t actually make the altruistic calculations consciously but it is in the back of our mind Hadza – isolated society, hunter/gatherers, the lowest voice pitches had the greatest number of children Women are almost guaranteed to have children (low variance) and can afford to be picky, no worries if they lose a mate there are a lot more to pick from. Men aren’t as likely to have children (high variance), should be more aggressive and fighting for choice Most homicides are done by men between the ages of 20-24 – typically this is the result of some sort of social competition, higher social status gains you more access to women so men are more likely to get aggressive (unemployed and poorest people have greatest chance of homicide) It is in your best interest to do something risky to leave behind your genes. Neuroscience 1 – Module The dualist perspective – separate mental processes of the mind from physical processes of the brain; the mind is a separate entity outside biology but in control of actions and thoughts; the physiological brain is the connector between the mind and body The neuron is the fundamental building block of the nervous system. Neurons are in the category of cells specialized for communication. They are organized into signalling pathways to communicate via synaptic transmission. The receptive zone – receives signals from other neurons, contains vital organelles. Dendrites – reach out to other neurons and receive signals to be released through the dendritic branch to the cell body where some signals will go on to be conveyed down the axon Once a neuron receives a signal it is passed down the axon (long fiber, some are very short some are a metre long, they run from spine to feet) Terminal boutons/terminal ends – at the end of the axon they reach out and make connections with receptive zones of nearby neurons to continue transmitting signals Glial cells – provide structural support, nourishment, and insulation needed by neurons Glial and neuron cells rest in a bath of ions, chemicals, and blood vasculature that makes up the brain. The neuron’s cell membrane is selectively permeable; it separates the intercellular fluid (in the neuron) from the extracellular fluid (surrounds the neuron). The selective movement of ions across the cell membrane into and out of the neuron is critical for neural communication. The resting potential The baseline imbalance of -70mV inside the cell Diffusion – tendency for molecules to distribute themselves evenly in a medium Electrostatic force – repulsion between ions with the same charge Leaky-potassium channel – always allowing K+ to pass through the membrane out of the neuron; major contributor to positive charges leaving leading to resting potential Sodium is on the outside, potassium is on the inside The negative proteins inside repel the Cl- so the Cl- stays outside the cell Voltage-gated Na+ channel – closed during resting state so only low concentrations of sodium flow into the cell Voltage-gated K+ channel – closed and used only during action potential The threshold Random fluctuations occur because of the surroundings – each neuron is connected to many other neurons and the influence of these and random ion flow causes a large enough change to bring it to threshold -50 mV is the threshold – this activates action potential Action potential Na+ channels along the membrane open, Na+ rush into the cell (inside becomes positive), this change (electrostatic force) causes K+ to be pushed out of the cell via the leaky K+ channels Overall, inside must be largely positive enough to open the voltage-gated K+ channels, more K+ leaves the cell and once a charge of +40 mV is reached inside the Na+ channels closed but K+ still leaves bringing it to even more negative than -70 mV causing the voltage-gated K+ channels to close and the neuron slowly returns to -70 mV during the refractory period in which no more action potentials can occur until this calming occurs. The sodium-potassium pump works to pull 3 Na+ ions from inside the cell out of the cell and replaces them with 2 K+ ions into the cell – not a huge actor in action potential but helpful in the recovering stage and requires lots of energy Action potential begins in the receptive zone where the cell body connections to the axon, rapid changes here cause changes in the ion concentrations surrounding the nearby channels, leading to action potential down the axon to the terminal boutons. Myelin (fatty tissue) coats axons (via glial cells) – this insulation allows for fast travelling of action potential down the axon Known as oligondendrocytes in the central nervous system or Schwann cells in the peripheral nervous system When action potential reaches the myelin sheath it jumps across using a process called saltatory conduction Between segments of myelin are open regions called Nodes of Ranvier which prevent the loss of strength since as the signal jumps through myelin sheath it weakens but at the nodes it is strengthened through ion channel cascades before continuing When sending a signal it is an all or none response – all action potentials by neurons are similar in strength and duration and once action potential is reached it continues to completion there is no such thing as half an action potential Different messages are encoded via the action potential frequency and pattern – how often an action potential fires. A strong signal will mean lots of sequential action potentials; a weak signal will mean fewer action potentials in the same period of time Synapse – the area of connection between the terminal bouton of the first neuron and the receptive zone of the second neuron; not a direct physical connection, special mechanisms exist for transmitting it Presynaptic neuron The terminal bouton contains neurotransmitters found within vesicles. When action potential reaches the terminal boutons, some of the vesicles move toward the cell membrane of the presynaptic membrane. The vesicle then fuses with the presynaptic membrane, spilling neurotransmitters into the extracellular fluid A single neurotransmitter can have many functions depending on the receptor on the postsynaptic neuron that it binds to. Some neurotransmitters include glutamate, GABA, serotonin, dopamine The synaptic cleft is the space between two neurons, contains other facilitating or inhibiting molecules some of which get rid of neurotransmitters Postsynaptic neuron Contains receptors on its surface for neurotransmitters to bind with to continue the signal transmission process Excitatory Post-Synaptic Potential (EPSP) Modifies the ion channels nearby Excitation – Na+ channels open allowing some Na+ to flow into the cell depolarizing the cell from -70 mV resting state to -50 mV threshold A single EPSP has a small effect therefore many must occur one after the other from the same presynaptic connection causing a slow climb to the threshold known as temporal summation OR multiple EPSPs can occur simultaneously from several different presynaptic connections within the receptive zone of the postsynaptic neuron known as spatial summation Everything cannot lead to EPSP though because if it did neurons would uncontrollably fire Inhibitory Post-Synaptic Potential (IPSP) Cl- channels open allowing Cl- to enter the cell, the neuron becomes hyperpolarized, brining it more negative and closer to resting then action potential/threshold The balance between EPSP and IPSP controls the extent to which the presynaptic signal affects the activity in the postsynaptic cell Neurogenesis – the birth of neurons Migration – the travelling of neurons to their correct location Differentiation – the transformation of unspecified cells into specialized cell types that differ in structure and function Maturation – the growth of neurons by establishing connections with other neurons Neurogenesis and neural tube development Began as early as 18 days after conception, the outer layer at the back of the embryo thickens forming a plate Neural tube – forms when this plate edges curl up and fuse together, this eventually closes and becomes the central nervous system (brain at the top and spinal cord at the bottom) and by week 20 it starts to look like a brain Ventricular zone – inside the neural tube and lined with founder cells that begin dividing once the tube is closed From day 28-42 the cells divide symmetrically – 2 identical founder cells are produced From day 42-125 the cells divide asymmetrically – one founder cell is produced and one cell that becomes a neuron or glial, migrating out from the ventricular zone Neurons are produced before glial cells with one exception – radial glial cells are produced before neurones. These radial glial cells are fibres that extend outward from the ventricular zone and end at the outer layer of the cortex. They are used by the neurons to move from the ventricular zone to the surface of the cortex. The brain grows inside out, the radial glial cells are always outermost, the neurons born last have to travel a lot farther than the first ones. Differentiation Pre-wired genetic determination – neural differentiation is partly determine by the location in the ventricular zone where a founder cell originated Input-specific environmental determination – input from other cells effects neural differentiation Using the two of these – if neuron is connected with a neuron from visual cortex it will probably end up doing something visually related and if a neuron that was originally for the visual cortex cannot be used because of a cataract in the eye it gets re-directed elsewhere After differentiation – dendrites, axons, and synapses grow; making connection with other neurons is essential to survival because more neurons are produced than required Unconnected neurons are pruned away – 20-80% of them Neurotrophic factors – “food” from other neurons to each other, limited amount, all the neurons are fighting for it The number of synapses increases until one year then it decreases for the rest of life span, allows the brain to retain only the most useful connections Order – neurogensis (birth), migration (to location), differentiation (determining job), maturation (making connections) Depression Symptoms – feelings of intense sadness, loss of motivation, trouble sleeping Neurotransmitters implicated in depression – tricyclic antidepressants inhibit the re-update of these back into the presynaptic neuron Normal process of recovering a neurotransmitter, inhibiting it increases the availability of serotonin and nonepinephrine and can dramatically alter symptoms Monoamine Oxidase (MAOis) – normally found in the synapse to break down serotonin but these inhibit the action of this preventing serotonin breakdown and making it more available Selective serotonin re-uptake inhibitors (SSRIs) – Prozac; neurotransmitter reuptake, have less side effects Depression is bigger than one simple chemical imbalance In some areas new neurons continue to grow throughout your lifetime this is stunted in depressed individuals and organization of neurons is disrupted Brain Derived Neurotropic Factor (BDNF) – vital for growth and survival of neurons Neuroscience 1 – Live Lecture Warning labels have dramatically decreased cigarette usage • Does this cause people to actually stop smoking? • Or is it only stopping new people from smoking • Answer – mild/moderate smokers decrease, stops new smokers, but heavy smokers show no change Trainspotting – covers the life of addicts how their addictions run their behaviour Case of unexpected low relapse rates – Vietnam war vets took opiates while there, became addicted, but when they returned they had low relapse rates because abuse is dependent on associations and environmental stimuli Ex – lemon -> citric acid -> salivation therefore lemon -> lemon cues -> salivation This is not an innate response as babies don't know they are eating something sour when they eat a lemon for the first time Ex – morphine -> analgesia -> hyperalgesia Environmental cues like preparation of the needle, morphine, etc so that when the drug is not administered the person is left in heightened pain sensitivity state – without the drugs they have all of the negative effects of the drug but no drug to balance the effects out – this causes withdrawal symptoms Low tolerance for alcohol vs high tolerance for alcohol is an inherited trait People with a higher tolerance for alcohol are more likely to become alcoholics Evolution – why would alcoholism evolve? Seems to be piggybacking on the reward circuitry that rewards positive behaviours like reproducing The centre in the brain for assessing cues and responses for beneficial or not behaviour knows that if it is beneficial, dopamine will be released. Ex – eating food, having chocolate, or having sex, will cause dopamine to be released. When you do heroin it hijacks the system to make you think it's a rewarding behaviour, releasing dopamine and not lighting up the part of the brain that would say “no this is bad” Chronic cocain reduces dopamine receptor and availability; a healthy brain will have a high density of dopamine but an addicted brain will have a lower density – one suggestion for this is that addicted people already have low receptors for dopamine and therefore can't get 'off' on chocolate or sex so they need drugs to get the same results Mirror neurons – neurons that are directly affecting behaviour, not expressed in crows, only humans and monkeys, they produce the same action potential response as any other neuron but they will also produce that response to watching someone perform the action Theory of mind – idea that what I know in my mind is different than what you know in your mind Mirror neurons could be responsible for transmission of cultural and social norms. They could also be responsible for mentally training yourself for things like spacewalking/moonwalking. Neuroscience 2 – Module Dorsal – back of the axis; top from the front view Ventral – front; “to or the belly” Rostral – towards the top of the axis Caudal – towards the bottom of the axis Medial – towards the centre of the brain Lateral – towards the outside of the brain ex – medulla in the hindbrain is divided into subregions such as rostral ventral medial medulla (towards the top, in front of the axis, towards the middle of the brain medulla) Natural Lesions Phineas Gage – metal bar exploded through his left cheek to the top of his skull – survived but went from an upbeat, calm and polite guy to selfish, erratic, irresponsible, and unreliable Induced Lesions In these case studies it is rarely isolated to one specific brain area, this problem can be solved by inducing lesions in animals Researchers destroy/damage/remove specific brain region and observe the result The problem with this is that it is still not specific enough because a variety of behaviours depend on a single brain part and vice versa Penfield – Canadian Neurologist Developed an alternative approache – electrically stimulate an area of the brain and observe the result on behaviour to build an anatomical map related to function Microelectrodes – a small electrode is inserted into the nervous tissue of a live animal with its tip held just outside the cell body of an individual neuron, neural activity is recorded as the animal does an activity, the pattern of firing reveals a neuron's particular functional role The patient would be awake working with him to probe the brain and locate and remove scarred tissue causing the seizures Structural Neuroimaging – to study large scale structures of brain regions CT Scan – x-ray slices of the brain are taken and pieced together to produce a quick picture of the brain MRI – magnetic fields align hydrogen ions throughout the brain and can be used to localize tissue precisely Functional Neuroimaging – to study brain function by finding the relationship between brain activity and mental functions PET – radioactive tracers are injected into the bloodstream, they are used in metabolic processes and detected by scanners (brain activity) fMRI – wearing an electrode cap, reads electronic signals in response to stimuli EEG – doesn't require radioactive tracers, measures the amount of O in t2e brain and makes the same assumptions as PET (places with more oxygen have more metabolic processes, however this isn't entirely accurate because the oxygen levels are a bit delayed) Hindbrain – region at base of brain that connects the brain to the spinal cord; information in and out goes through cranial nerves through the spinal cord at the base of the brain Medulla – vital functions, breathing, digestion, regulation of heart rate Pons – relays information about movement from cerebral hemispheres to cerebellum; some of its nuclei are in the reticular formation; involved in emotion and audition Reticular Formation – involved in arousal and motivation as well as circadian rhythms (changes in your body environment that prepare you for the day at certain times ie – getting up in the morning and falling asleep at night) o ascending reticular formation – arousal, motivation, responsible for conscious experience, circadian rhythms, damage here leads to coma o descending reticular formation – posture, equilibrium, motor movement o Cerebellum – the “little brain”; maestro of the orchestra for coordinating all movement; involved in motor regulation – commands pass through here telling muscles to contract and then return to the cerebellum for immediate error correction; if there is cerebellar dysfunction the individual will have exaggerated, jerky movements and be unable to hit targets Midbrain – middle region of the brain involved in processing visual and auditory information Tectum – in the dorsal portion; contains the superior and inferior colliculi (perceptions and actions) o superior colliculi – involved in eye movements and visual reflexes; receives visual input o inferior colliculi – involved in auditory integration; receives auditory input Tegmentum – in the ventral position; contains nuclei of the reticular formation, the red nucleus, and the substantia nigra o red nucleus – vital for the production of movement; in vertebrates with less complex brains it is the most important movement structure because it projects directly onto the cerebellum and spinal cord; in humans it is a relay station for information from higher motor areas to the cerebellum and spinal cord; in babies/infants it controls lots of motor behaviours o substantia nigra – involved in motor planning, learning, reward seeking;contains neurons that produce dopamine; drug abuse will increase dopamine, damage to this part will decrease dopamine (can lead to Parkinson's) Forebrain – uppermost and largest brain region composed of several structures the most prominent being the cerebral cortex; has the most complex functions – emotion, memory, perception, and thought Hypothalamus – directs stress responses, regulates energy and metabolism by influencing feeding/digestion/metabolic rate, regulates hormonal controls for mating/pregnancy lactation, contains neurons that regulate hormones o four f's – fight, flight, feeding, reproduction Pituitary – inferior to the hypothalamus; is the master gland; involved in hormone regulation o anterior pituitary gland – receives signals from the brain via the hypothalamus to release hormones to regulate other endocrine glands (thyroid, testes, etc) o posterior pituitary gland – extension of the hypothalamus; releases oxytocin (lactation, birthing, love, trust) and vasopressin (blood hormone that regulates thirst by interacting with the kidneys to regulate glucose levels) Amygdala – controls fear responses – receives info from the thalamus to decode emotions and in particular stressful and threatening stimuli; dysfunction of the amygdala causes deficits in fear responses such as PTSD Hippocamus – involved in memory formation, the ability to hold short term memory and transfer into long term; is connected to the amygdala which explains why fear inducing memories are strong; involved in spatial learning, contains a spatial map of the world around us; new neurons continue to form here into adulthood as new memories are formed; damage to this area can cause Alzheimer's and amnesia Cortex – ultimate control and information processing centre; from an evolutionary perspective it is the newest part of the brain To increase surface area it has gyri – the ridges (outward bulge), sulci – the indents (the gaps between them), and fissures – very deep sulci which divide the major areas of the cortex Four lobes – occipital, temporal, parietal, frontal Occipital Lobe – visual processing, contains primary visual cortex, damage causes blindness Temporal Lobe – contains the primary auditory cortex; involved in higher visual processing – processing the form and identity of visual stimuli; involved in processing of language and memories; damage causes amnesia, speed and auditory processing problems Parietal Lobe – contains the primary somatosensory cortex – processing of touch begins here; involved in complex visual and spatial functions for processing location and movement of visual objects with help from the occipital lobe; also used in spatial representations of the world – useful for guiding eye and body movements and attention; damage causes deficits in somatosensory processing or loss of sensation as well as deficits in orienting movements and attention to spatial regions Frontal Lobe – the most complex and least understood; contains the primary motor cortex which is where motor commands originate; most complex decision making processes occur here as well; involved in language, strategy formation, inhibition, and manipulation; little kids lack inhibition and have underdeveloped social skills and forward planning this is because their frontal lobe isn't fully developed; damage causes spontaneous inappropriate behaviours, motor deficits, loss of motivation, deficits in decision making, learning, and difficulty understanding language Brain Lateralization/Asymmetry – functions are specialized to one side of the brain Double Dissociation – lesion studies demonstrate these; damage to a cortical region on one side of the brain produces a specific behavioural deficit whereas others don't Language on the left; Spatial on the right Speech deficit aphasia – lesion in the left frontal lobe (Broca's area) – vital for motor production of speech Left temporal gyrus (Wernicke's area) it is important for language comprehension Corpus Callosum – carries information from one side to the other, the connection across the hemispheres Left – words, letters, language, sounds, verbal memories Right – geometric patterns, faces, emotional expressions, non-language sounds (music), non-verbal memories “Split Brain Syndrome” - example - if you show a cup into the left visual field that corresponds to the right brain which is “spatial” so the person can find it spatially but cannot name it Neuroscience 2 – Live Lecture 3 classes of neurons - sensory neurons, motor neurons (muscles), interneurons (most abundant type of neuron in the central nervous system, they modify the signal carried by sensory neurons) Knee-jerk Reflex - - have a leg dangling over the table, try to strike under the knee cap. Will cause reflective response that causes leg to click outwards - striking the patellar ligament, sensory neurons travel to spinal cord. 1. Sensory neuron will synapse to motor neuron, will then send signal to leg that causes it to flex. 2. Sensory => interneuron => motor: causes it to relax. They counteract each other. Brain:-- very expensive metabolic “real-estate”, uses many resources (15% of cardiac, 20% of total oxygen use, it can use up to 25% glucose) - young deer, after a few days, they can have a fully developed brain, unlike human baby brains. - human baby brains are undeveloped when born. Will then develop. Case studies and the connected brain (where things might go wrong) give us opportunistic way to study this unhealthy brain function Sleep paralysis Hindbrain – PONS = connects the brain stem to the cerebellum. Controls eye and body movement, also plays a role in sleep and arousal. Coordinates balance causes rem induced rem stage paralysis. (pons paralyzes you). Nightmares; you feel like you’re paralyzed. Inhibited motor function paralysis does not completely wear off when you wake up. Pons inhibits motor signals that are sent out. built in mechanism because you might be dangerous when you sleep walk/act out during sleep- pons develop at around 1 year Amygdala-FFG (Capgras’ Delusion): young male has been in coma for 3 weeks, physically, mentally he’s fully recovered, one weird thing is that he recognizes his parents/acknowledges, but seems uncomfortable (something is not right)/acts cold & standoffish They look EXACTLY like my parents, but they aren’t. (they’re nice people too). Believes they’re imposters - can last up to two years this type of delusion occurs when he directly interacts with his parents. Phone calls are fine100/150 years ago, they would believe that he’s a witch or there must be some Freudian thing (resentment of parents) what’s happening in the neuroanatomy? Amygdala – assess the emotional significance of a stimulus - will cause fear when observing a bear when you’re camping. Arouse you to feel emotional significance when you see someone you know really well, when you see your parents, your boyfriend, your bestfriend, your girlfriend FFG – neurons in the FFG respond to faces, information from FFG travels to amygdala. Amygdala will tell you if the face is significant what happened was that there’s a disconnect between the FFG and the amygdale Explanation for the person is that this person looks like my father, but since I don’t feel anything, could not possibly be my father. Recognition without emotion = Galvanic skin response (objective test) Delusion does not occur with auditory stimuli = while he is hearing the other person’s voice, the medulla signal is intact. Visually, the absence leads to odd feeling. Visual systems will trump all other systems Brain creates a running narrative to explain stimuli and events every behaviour you do is justified ie. I had ice cream today… except I’m trying to lose weight. But like I went on a run yesterday/went to the gym, so I’m fiiiiineeee we lie to ourselves all the time, self-serving bias (above average effect) Ex. ice cold water bath. Told ½ a group after exercise, that if you have a type 2 heart, you can keep your arm in the cold water longer (10 secs longer). Told other ½ a group after exercise that if you have a type 2 heart, you will be more sensitive to cold water (10 secs less) coming up with complex explanations to justify behaviour 3)Hemispatial Neglect: brought on in stroke patients 60 year old woman. Specific region of brain lacked oxygen and glucose very meticulous about appearance, but now she goes through her normal routine but she only seems to be paying attention to the right side of the body, right side makeup, right side hair, only eats things on the right side of plate left side of the world no longer exists Behavioural Test: only right side is being noticed. Damage to the right parietal lobe loss of function in the parietal lobes (inferior parietal lobe) = spatial layout of the world, person can see both visual field, it’s just that they’re not paying attention to the left visual field - Left hemisphere attends to right side; right hemisphere attends to both sides - Damage to left hemisphere is not as bad as damage to right because right hemisphere attends to both, while left hemisphere only attends to right side. Neuroscience 3 – Module Cognitive Neuroscientists - neuroimaging to trace neural processing routes understand abstract processes Behavioural Neuroscientists – neural processes behind behaviours for rewards/sex etc; hunger and safety mechanisms Neural Plasticity Rehabilitation can cause recovery from brain trama – dramatic demonstration of neutral plasticity. Everyday neural plasticity – allows the brain to adapt to incoming stimuli and rewire itself to optimize interactions with the outside world Rats and Environmental Enrichment Experiment Rats exposed to complex environments made the animals better problem solvers – this caused enduring changes in the physical structures and functional organization of their brains These enriched rats had a richer neuron network with more connections vs those who were raised in an impoverished environment Rats raised by caring mothers became less stressed vs those with mothers who didn't engage in maternal care – these were matched with brain changes including increased expression of glucocorticoid receptors in adult rat's hippocampus The brain is adaptive and can detect contingencies between stimuli. Connections between individual neurons can be changed and combinations of connecting neurons can be grouped as processing units; everything is built from sequential activation of neurons - “neurons that fire together, wire together” Long Term Potentiation – strengthening of the connection between two neurons and this effect can last an extended period of time (a few minutes to entire lifetime); an increase in synaptic efficacy – the presynaptic neuron becomes more efficient at generating a larger response in the postsynaptic neuron measured by change in the amplitude of EPSP; mechanism for Hebbian learning Properties – rapid and long-lasting (time for new memories to form), input specific (facilitates only the synapses activated during the original stimulation), associative (it can strengthen inputs from multiple pathways if they are active simultaneously) ex – weak stimulation of pathway 2 doesn't trigger LTP but weak for 2 and strong for 1 means both are strengthened Following activation by brief, repeated, bursts of high frequency stimulation, a single test pulse could make it easier for adjacent cells to fire action potentials Mechanism of LTP Glutamate – it binds to the AMDA receptor – this binding causes the channel to be opened allowing positive ions into the cell (Na+), this depolarizes the cell moving it away from the -70mV resting potential and closer to the -50mV action potential threshold, this can cause short-lived ESPS's – this needs to lead to sufficient depolarization that unblocks the Mg+ on the NMDA receptor so that Ca+ can enter and LTP can start The concentration of Ca+ ions in the postsynaptic cell must exceed a critical threshold, this can only occur when glutamate binds to NMDA, this cannot happen during the resting state because the NMDA binding site is blocked by Mg+ so that Ca+ cannot enter the cell Calcium – promotes the expression of more AMDA receptors in a specific region of post-synaptic neuron, this can last days/weeks/months LTP requires - Glutamate to bind to both the AMPA and NMDA receptors, if it bonds only to AMPA then it is a simple synaptic transmission, when it bonds to both it causes LTP Requires the two main events – postsynaptic activity to remove the magnesium block and presynaptic activity to release glutamate LTD – long term depression exists to decrease the sensitivity of the synaptic connections – LTD+LTP = why neurons that bind together, fire together From synapses to behaviour How do these synapses lead to behaviour? Study through the Aplysia fish/octopus-y thing, it has 20 000 neurons compared to a billion so it is a simple model system It has a gill withdrawal reflex – at rest their gill is extended outward to assist in O2collection but in response to danger it retracts organs for safety – simple reflex mediated by small circuit of neurons Habituation – decreased response to repeated/constant stimuli Strength of gill withdrawal reflex becomes smaller after repeated stimulation; sensory neurons at skin receive signals from the outside world, synapse with motor neurons that return to the gill to control the withdrawal behaviour The presynaptic neuron fired just as many action potentials and the post synaptic neuron was just as sensitive but the presynaptic neuron was releasing less neurotransmitters – fewer vesicles were fusing with the membrane and this could last for weeks Classical Conditioning – a separate area of the body (mantle-CS) was stimulated before stimulating the gill withdrawal, predicting the gill withdrawal (US) eventually the mantle alone elicited the gill withdrawal NMDA/Calcium – stimulation from the mantle causes light depolarization of postsynaptic neuron releasing the Mg+ blockage at the NMDA site so that Ca+ can go into the cell and LTP can occur – NMDA is the contingency detector There is a direct link between cellular mechanisms and behavioural output. Curious Case of HM At age 7 he fell, hit his head, had seizures to the point where he couldn't function normally. He had experimental surgery to remove his temporal lobes but most of the hippocami were also removed. He could live normally and had all his old memories but his short to long term memories didn't work – permanently stuck in 1953/at age 27 Procedural Memory – memories for actions, sequences, skills Diverse neural correlates – outside of awareness and can be difficult to explain to others; are very diverse, ex – how to ride a bike, swim, play instrument HM was capable of learning new things, but couldn't remember practising them Damage to the cerebellum and striatum – damaged motor skills/Parkinson's Declarative Memory – memory for facts, knowledge, and personal experiences; prone to forgetting but can be improved through rehearsal Involves hippocampus, cerebral cortex, and parahippocampal region parahippocampal region – begins in cortex where information you are currently working with is processed, then it goes to this region for intermediate storage then to the hippocampus for long term storage Hippocampus has three layers of representations lowest – representation of the current experience in context of the entire even middle – links these together based on common places/episodes experienced in the past final – flexible declarative memory organized according to most important information is permanently stored Neurons fire in specific locations – ex – specific cells fire in relation to specific location of an animal, independent of the behaviour being performed, known as place cells. Hippocampus receives information about the outside world to create a cognitive map. Each cell fires when animal is in a particular region of this map. Some also fire in response to behaviours being performed in certain locations. Neuroscience 3 – Live Lecture Brain in a jar problem – “the matrix” – everything we see/hear how can it really be? Heuristics and prior knowledge – a bat and a ball cost $1.10, the bat costs $1 more than the ball, how much does each cost? Most people would say the ball costs 10cents and the bat costs $1.10 but that equals $1.20 – but children would know that the ball is 5cents and the bat is $1.05 This is because of our processing skills. Visual top-down processing – we assume the easiest (availability heuristic) Language segmentation is a problem for people learning a new language – an audio top-down processing Even if we are given ambiguous information we can still determine what is going on – “how to recognize speech” is what you’ll hear from “how to wreck a nice beach” because we will perceive what actually makes sense as opposed to what we really here All the information we use to evaluate our world can be understood through basic neural processes: 1) Learning motor responses Phantom limb syndrome You no longer have a left hand but how does the brain cope – by reducing input from your left hand. However some people still feel the missing hand as if it was moving in unison with the right hand, but with a slight lag. There is still activity in the brain even though the hand is missing. Sensory motor cortex activity Sometimes the phantom limb does weird things like making a weird gesture without any control or feeling extreme pain from the phantom limb How can we undo this neural activity? Show visual stimuli – place hands in front of the patient and in front of a mirror, they can see a mirror image of their right hand but it looks like their left hand – so they can practice exercising, clenching, and stretching their left hand it appears as though their left hand is relaxed – this visual feedback led to a release in the sensory motor cortex relating to that limb Enhanced input and plasticity Becoming an export in your sport takes about 10 000 hours – your brain will have more neurons set to the motor processes involved in that sport. Experiment – tested the brains of musicians in an intense music school – the amount of practice they put in was directly proportional to their performance Those who put in 10 000+ hours became top performers, those who put in ~5000 hours were okay performers and most became teachers, and those who put in ~2000 hours did not end up in the music industry 2) Multiple memory modules Cortex -> hippocampus -> declarative memory Cortex -> straitum and cerebellum -> procedural memory Cortex -> amygdale -> emotional memory Double Dissociations Single case studies are not controlled experiments, damage might not be localized. We can fix this by lesioning one part of the brain which allows us to focus on a certain memory task. Experiment 1 – radial arm maze st 1 time – the mouse explores it, if you go to the right arm you get cheese – all he has to remember is to go to the right declarative memory They lesioned out specific parts and without the hippocampus, this task was impaired Esteriment 2 – cued maze 1 time – whenever the mouse goes down a path with light, they will get cheese – procedural memory This was not possible without the straitum and cerebellum Esteriment 3 – salience maze 1 time – mouse had two paths into mazes, one had nothing in it, the other was full of lots of exciting stimuli to make the mouse happy. Without the amygdala they were unable to pick the happy one, with the amygdala they picked the happier path. A collaboration in brain activity Patient – CK – we don’t notice the integration and collaboration in our minds because it is so smooth Had “object agnosia” – he can imagine anything and draw them but he cannot categorize them “draw a guitar” he can draw it but he doesn’t know what it is or what it is used for Vision – Module Nearly 1/3 of the brain is devoted to processing visual information. Three Properties of Light Amplitude – measure of brightness, more amplitude = more light is reflected/emitted therefore it is brighter/more intense Wavelength (nm) – distance between peaks of successive waves, affects the perception of colour; wavelength and frequency are inversely proportional; the visible spectrum goes from violet (360nm) to red (750nm), below violet is ultraviolet (bees), above red is infrared (snakes) V = λ f Purity – affects the perception of the saturation (richness) of the colours; if light is made from a singe wavelength it is pure light/completely saturated colour; if light is made from a combination of wavelengths is white/completely desaturated; what we see are mixtures of wavelengths The Eye Cornea – beginning of focus; light passes through the curved cornea first; transparent window at the front of the eye, the rest of the eye is covered by white part called sclera Pupil – opening in the eye; round window (black dot in the middle of the eye) Iris – controls pupil size; the coloured part; is a band of muscles that is controlled by the brain so that if not enough light is reaching the retina the muscles can dilate the pupil to a bigger area or constrict it for lack of light Lens – final focusing; transparent structure on the retina Everything is upside down and reversed from left to right but the final image is a product of the brain activity that lets us see right side up. Accommodation – change in shape of lens to focus on objects; flexible piece of tissue that’s shape can be altered by the surrounding muscles allowing it to focus on objects that are close or far away – for close objects the lens gets fatter/rounder to produce a clear image, for far objects the lens gets elongated to focus the image on the back of the eye After the lens, light passes through the vitreous humour – clear, jelly-like substance that comprises the inner eyeball, then it lands on the neural tissue (retina) at the back of the eye. The physical stimulus of light is first translated into neural impulses. Retina – paper thin sheet covering the back of the eye, contains 3 different neural cell layers Layer 1 – photoreceptors – responsible for translating physical stimulus of light into a neural signal that the brain can understand; must pass through other 2 layers which are transparent (this backwards layers process is because photoreceptors get their nutrients from the retinal pigment epithelium [RPE] which are at the back of the eye) Rods – plentiful; operate at low light intensity, good for night vision, provide no information for determining colour, give poor visual acuity, there are no rods in the fovea but lots around the fovea, they are good for peripheral vision - if you’re trying to see something in a dimly lit environment you’re better off looking slightly to the side to use your rods instead of directly at it using your cones Cones – not as many; operate at high light intensities, day vision, provide sensation of colour and good visual acuity (sharpness of detail), become more concentrated towards the fovea (tiny spot in the middle of the retina containing only cones) – when we want to see something in detail we move our eyes so the image falls directly onto the fovea Photoreceptors contain photopigment a complex molecule that is sensitive to light – there are 4 different kinds, 1 for rods and 3 for cones but they all work the same way. A photo of light is absorbed, it changes the chemical state of the photopigment and splits it into its 2 component molecules, setting off a biochemical chain reaction leading to an electrical current flowing across the membrane. Light is now in a currency that the brain can understand/process. Once the splitting has happened, high energy molecules within the photoreceptor cause the two molecules to recombine so that the photopigment can react to light again but there is a brief recovery time where it cannot react to light. Bipolar cells receive the photoreceptor signal; ganglion cells collect information from a larger segment of the retina and the axons of these cells all converge on one point in the eye called the optic disc and then leave the eye to join the optic nerve which travels all the way to the brain. Before the optic chiasm it is known as the optic nerve but after the optic chiasm it is known as the optic tract. All the first layer sends the information to the next layer via transmitter substance (bipolar cells) then to the ganglion cells. The second and third layers consist of ganglion cells, there is also a blind spot where there are no photoreceptors. The optic disk is the point where all cells/light converges. OVERALL – light passes through layers 3 and then 2 to reach 1 (photoreceptors) then is sent back to 2 and then 3 then out to the brain. Horizontal and amacrine cells – allow areas within the retinal layer to communicate with each other; allow information from adjacent photoreceptors to combine because information from 130 million rods/cones converge to travel along only 1 million axons in the optic nerve – therefore some processing is done in the retina Lateral antagonism/inhibition – whenever a retinal cell is stimulated the cell sends signals to the brain but also sends messages sideways to neighbouring cells that inhibit their activation – perceptually results in edges of objects being easier to detect. This is done through horizontal cells, activated by photoreceptors, and amacrine cells, activated by bipolar cells. Photoreceptors are divided into “groups” for one ganglion – each group gets assimilated into one signal that affects the ganglion down the line. In the fovea a group may only contain one cone (small area) so a lot of detail is preserved but usually the groups are larger as we move to the peripheral vision explaining why visual acuity is low for peripheral vision. Receptive field – collection of rods and cones that, when stimulated, affects the firing of a particular ganglion cell; come in a variety of shapes and sizes but most are donut shaped in such a manner that the light falling in the center of the donut will either excite or inhibit the cell and the light falling in the surrounding area will have the opposite effect to the center. Excitation/inhibition is determined by the rate at which the cell fires compared to the baseline (normal cell rate firing without light signals). When it is excited the rate of firing is greater than the baseline, when it is inhibited the rate of firing is less than the baseline. When a receptive field is stimulated the ganglion cell sends signals to the brain. The visual field receives information from both eyes and both hemispheres receive information from both eyes but the right visual field goes to the left cortex and vice versa. Regions of the retina closest to the nose cross over to the opposite hemisphere and the optic chiasm is the point of crossing over. Information arrives in the opposite hemisphere and splits into two pathways. Most travel along the main pathway and synapse in the lateral geniculate nucleus (LGN) which is a part of the thalamus that receives visual information. After being processed it is sent to the parts of the occipital lobe that make up the primary visual cortex. The first stop is the LGN, these cells have receptive fields made of ganglions so smaller bits of information are again combined into one overall signal. The LGN is made of 6 layers and information from a specific eye and specific subpath goes to each layer then is sent to the occipital lobe. Within the main pathway there are two specialization subdivisions: Magnocellular pathway – 2 LGN layers, processes movement information Parvocellular pathway – 4 LGN layers, deals with colour and form information A smaller portion of axons from the retina detour in the midbrain to the superior colliculus and then information is sent up to the thalamus and then the occipital lobe or down to structures in the brain stem. This is involved in visual input coming from other senses as well as localizing objects in space through head and eye movements and guiding those movements. Occipital lobe Over 20 areas but the most is concentrated on the V1 (primary visual cortex - PVC) Extrastriate cortex – visual processing areas outside the striate cortex PVC is made up of many receptive fields of LGN cells which are made up of ganglion ells so information is again processed into a single target (photoreceptors -> ganglions -> LGNs -> V1s) The PVC contains a topographical map of the retina – neighbouring locations in the retina project to neighbouring locations in the visual cortex. Contains 6 layers – the LGN projects directly onto layer 4 – information is carried into the other 5 layers from there. PVC is organized into cortical columns, most neurons have a stronger response to one eye than the other; all neurons in one column maintain this presence Cortical neuron – first site of binocular processing All of this is sent to the extrastriate cortex then split into the dorsal vs ventral streams Dorsal – the where pathway; where objects are; involved in depth, motion, location; ends in the parietal lobe Ventral – the what pathway; what the object actually is; identify colour, form,; ends in the temporal lobe As information is processed, it is compressed. Neurons generally respond strongly to a specific attribute. Eye Evolution 1 – simple light sensitive patch 2 – curved “cup” eye – formed into a slight depression for direction detection of the light, found in clams 3 – crude lens – allows for focusing and accommodation – processes visual input at different distances; more transparent lens, better curvature Cumulative selection – small changes were made to the existing eye and then new small changes were made to the modern eye and so on – all built upon each other Precambrian – crude light sensors – hard to run away from predators because couldn’t sea Cambrian – better for hunting so arms race between prey and predators to develop better vision/locomotion skills The advantages of the modification must outweigh the energetic costs to the system growing. Typically, better eyes = easier to find food, shelter, run from predators etc The type of eye depends on the environment – cave dweling crayfish (energetic cost of eyes would outweigh the benefit, they don’t need intense eyes) vs open-water crayfish (energetic cost of eyes is less than the benefit, need to be able to see) Eyes -> light sensing (worms) Eyes -> image forming -> compound eye Eyes -> image forming -> simple eye Compound eye – found in arthropods (insects/crabs); made of ommatidia – an arrangement on individual tubular units that each point in a slightly different direction to gather the light that lays directly on it; make a single image from putting together several separate signals from each ommatidium together; good at detecting movement but only at close distances Simple eye – found in vertebrates and molluscs; have eyeball, lens and retina; vary in terms of position, shape, size, and photoreceptor distribution Pupil shape – primates are circular – humans can only increase in brightness of retinal image about ten times – can`t see a wide range of illumination conditions; catshave a slit (oval) pupil which varies much more in size (ten times better than humans) therefore it can capture more light in dark environments. Vertical slits – cats, climbing snakes – if an animal’s life is dependent on above/below Horizontal slits – horses, sharks, land snakes – if an animal’s life is dependent on seeing on the horizon Eye size – two functions – resolution (acuity) and sensitivity (ability to get enough light) Larger eyes are better at both Cats/horses/owls have big eyes for good sensitivity – good night vision, but poor visual acuity Humans/hawks have big eyes for good resolution – good visual acuity, poor night vision Largest eye = deep sea squid Hawk eyes: 1) have wider daylight pupil – allows more light to enter the eye for better sensitivity 2) more densely packed photoreceptors – improves acuity 3) built-in crude telephoto system – magnifying the image they’re looking at Eye location Eyes on either side of head – laterally directed – rabbits/prey animals – produces a large total view, animal can see all around the body without turning its head; causes two separate fields with little binocular overlap – poor depth perception Both eyes directed towards the front – humans and predators – narrow field of vision because both are looking at the same scene but lots of binocular overlap – good depth perception, good for hunting Fovea Placement Fish – need to focus directly on what’s in front of them so fovea is part of the retina that processes what is right in front of them Seabirds/grassland mammals – have to pay close attention to what is happening close to the horizontal plane so the fovea is a horizontal streak cross the eye Owls/birds of prey – fovea is in the retina – the area viewing the ground because that’s where there prey is, they have to turn their head upside down to see up Pigeon – 2 regions – one directly in front of them to guide pecking behaviour and one more peripheral for locating distant objects End development 2 prenatal month – eyes formed 6 prenatal month – reacts to light, randomly fires of retinal cells also occurs during prenatal period that is critical for the organized wiring of the retinal cells determining how neighbouring cells will be connected together It is not well developed because there is much additional work that has to be done to make vision fully functional and requires system being used (cannot be done before baby is born). The lens muscles are weak – newborns cannot focus as much and the clarity of the image is blurred because the pupil doesn’t react to changes in light as well. By about 3 months because of exposure the infant’s ability to focus is almost adult like Newborn retina density is low especially true for the fovea – retina cells don’t reach adulthood until after four years – the optic nerve and visual cortex also require years to mature Preferential looking technique – infant’s natural preference to look at a card that has sharp contrasts between light and dark like a black/white card compared to a uniformly grey card – if the stripes become closer and closer the baby won’t prefer it anymore because it can’t tell the difference between that and grey due to it’s poor visual acuity Visual evoked potentials – characteristic pattern of electrical brain activity that accompanies a new visual stimulus. Different stimuli evoke different responses so we can tell if a baby can discriminate between two images that differ in visual details At birth acuity is bad but it improves dramatically by 6 months but it doesn’t reach full acuity until around 4-6 years and by 11 years the visual brain area development is complete Vision – Live Lecture Sensations convert energy into nerve impulses – what is actually happening in the brain with these impulses? – Perception Top-down processing occurs from experiences
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