Psychology 2220: Cognitive Neuroscience (All lecture notes).docx

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Western University
Psychology 2220A/B
Scott Mac Dougall- Shackleton

Chapter 1 - Biology as a Neuroscience neurons: cells that receive and transmit electrochemical signals 100 billion neurons in the brain neuroscience: scientific study of nervous system FOUR MAJOR THEMES Thinking Creatively about Biopsychology we must think creatively to overcome conventional thinking Clinical Implications clinical: pertaining to illness or treatment much is learned from the diseased or damaged brain and discoveries often have relevance to treatment of brain disorders Evolutionary Perspective evolutionary perspective: environmental pressure leading to evolution highlights important insights comparative approach: trying to understand biological phenomena by comparison of different species Neuroplasticity neuroplasticity: adult brain continually grows & changes according to individual’s experiences and genes single most influential discovery in modern neuroscience 1.1 WHAT IS BIOPSYCHOLOGY? biopsychology: scientific study of the biology of behavior emerged in the late 1940s preferred term: neuroscience psychology: scientific study of behavior all activities of an organism as well as internal processes underlying them The Organization of Behavior by Hebb (1949) played a key role in emergence of biopsychology proposed that psychological phenomena is produced by brain activity proposed that when associative learning takes place there is a change in connectivity among neurons learning occurs via changes in the brain wherein weak synapses become stronger used eclectic approach 1.2 RELATION BETWEEN BIOPSYCHOLOGY AND OTHER NEUROSCIENCES - biopsychologist: neuroscientists who research behavior purpose: to produce and control behavior biopsychology uses knowledge and tools of other disciplines and applies them to neuroscience neuroanatomy: study of structure of nervous system neurochemistry: study of chemical bases of neural activity neuroendocrinology: study of interactions between nervous and endocrine system neuropathology: study of nervous system disorders neuropharmacology: study of effects of drugs on neural activity neurophysiology: study of functions and activities of nervous system 1.3 TYPES OF RESEARCH CHARACTERISTIC OF THE BIOPSYCHOLOGICAL APPROACH Human and Nonhuman Subjects rats, mice, cats, dogs, non-human primates studied differences between brains is quantitative, principles of brain function clarified by studying non-humans use comparative approach: simpler brains- reveal fundamental brain- behavior interactions fewer ethical restrictions advantage of using humans: follow instructions, report experiences, cheaper Experiments and Nonexperiments experiment: used to find causation by creating two or more conditions of testing between-subject design: different groups of subjects tested under each condition within-subject design: same groups of subjects tested under each conditions independent variable: relevant difference being compared dependent variable: variable being measured to assess effect of independent variable confounded variable: unintended difference if more than one difference affected the dependent variable Coolidge effect (Lester & Gorzalka, 1988): male unable to copulate with one sex partner is often able to copulate with another limited confounding variable and discovered females were more vigorous with unfamiliar males males and females have a lot more in common than people appreciate non-experiments: researcher does not control variables of interest quasiexperimental studies: studies of groups of subjects exposed to conditions of interest in the real world eg. brain damage in alcoholics potential confounded variables uncontrolled eg. random assignment of subjects to conditions case studies: studies focusing on a single case or subject most in-depth generalizability (degree to which results are applicable to others) is low Pure and Applied Research pure research (basic/fundamental): motivated primarily by curiosity of research research of most breakthroughs in science eg. atomic bomb, Penicillin, steam engine, moon landing, human genome project applied research: intended to bring direct benefits to humankind necessary for short term gains most inventions or discoveries were improvements over earlier works eg. radio, telephone, light bulb 1.4 DIVISIONS OF BIOPSYCHOLOGY 6 major divisions much overlap with approaches often, biopsychologists follow more than one approach Physiological Psychology physiological psychology: neural mechanisms of behavior controlled experiments with direct manipulation of the brain surgical/electrical manipulation most common subjects: lab animals pure research: contributes to development of theories on neural control on behavior rather than research that is of immediate practical benefit Psychopharmacology psychopharmacology: controlled experiments of the effects of drugs on the brain and behavior subjects: usually lab animals, sometimes humans mostly applied research: development of therapeutic drugs or to reduce drug abuse Neuropsychology neuropsychology: studies psychological effects of brain damage in humans subjects: almost exclusively case-studies and quasiexperimental studies of patients with brain damage from disease, accidents or neurosurgery most applied discipline clinical emphasis Psychophysiology psychophysiology: studies relationship between physiological and psychological processes in human subjects eg. visual tracking abnormal in schizophrenics physiological activity recorded from surface of body electroencephalogram: recording of electrical activity along the scalp autonomic nervous system: division of nervous system regulating body’s inner environment Cognitive Neuroscience cognitive neuroscience: studies neural basis of cognition ie. thought, memory, attention, complex perpetual processes subjects: humans non-invasive studies fMRI: recording images of activity from the living human brain while the subject is engaged in a cognitive activity Comparative Psychology comparative psychology: compares behaviors between different species deals with biology of behavior rather than neural mechanisms of behavior explicitly comparative and evolutionary methods to understand both evolution and mechanisms ethological research: studied in lab and natural environment two subfields: evolutionary psychology: understanding behavior considering evolutionary origins behavioral genetics: study of genetic influences on behavior 1.5 CONVERGING ORIGINS converging operations: combining biopsychological approaches Korsakoff’s syndrome: severe memory loss while suffering little to no symptoms otherwise eg. Jimmie G- his case was caused by thiamine (vitamin B) deficiency 1.6 HOW TO STUDY UNOBSERVABLE WORKINGS OF THE BRAIN scientific method: system of research by observation scientific inference: empirical study of measurable observable events to explain the unobservable 1.7 CRITICAL THINKING ABOUT BIOPSYCHOLOGICAL CLAIMS critical thinking: recognizing weakness of existing arguments eg. Moniz’s failed psychosurgery experiment eg. Delgado’s claim that caudate taming center controlled aggressive behavior - Morgan’s Canon: when there are several possible explanations, go with the simplest one Chapter 2 - Evolution, Genetics, and Experience zeitgeist: general intellectual climate of our culture we are all products of a zeitgeist 2.1 BIOLOGY OF BEHAVIOR: FROM DICHOTOMIES TO INTERACTIONS Physiological or Psychological? a lot of false dichotomies stem from the theories of Descartes he divided physical matter which can be scientifically investigated from the human soul, which he believed did not obey any natural laws divided soul from biology of organism even though the mind is a product of the brain believed that nerves led up to tubes which control the body hydraulically believed animals only have reflexive behaviors Cartesian dualism: mind and brain are distinct entities conscious mind can operate independent of biological operations of the brain Inherited or Learned? nature-nurture issue: thinking about behavior in terms of learning or behavioural capacities Watson, father of behaviorism believed in nurture ethology: study of animal behaviors in the wild primarily interested in natural behavior instinctive behaviors: behaviors that occur in all like members of a species Skinner believed in a learning basis of all behavior Watson supported environmental determinism Lehrman studied hormonal control on behaviors extremely opposed instinct: even ―instinctive‖ behaviors must develop any behavior that is learned must have a genetic basis Problems with Dichotomes physiological vs. psychological thinking fails: brain damage has an impact on psychological functioning asomatognosia: deficiency in awareness of parts of one’s own body results from damage in right parietal lobe eg. Oliver Sacks non-human animals show some human-like abilities eg. chimp self-awareness nature vs. nurture thinking fails: environment influences behavioral development behavior is a product of interaction between nature and nurture all traits depend on expression of inherited genes experience continually modifies genetic expression model of biology of behavior: interaction between: genetic endowment experiences perception of current situation 2.2 HUMAN EVOLUTION evolution via natural selection: biological changes over time Darwin proposed natural selection his evidence: fossil evidence homologous and analogous striking similarities among living species suggesting common ancestors universal genetic code DNA major changes by selective breeding artificial selection Grant’s study of evolution of finches was a direct observation of evolution in progress natural selection: heritable traits associated with high rates of survival success variation among individuals much of this variation is inherited more individuals are produced than can survive heritable traits increase the probability of offspring things that ―work‖ will become more common in future generations fitness: an organism’s ability to survive and reproduce Evolution and Behavior behaviors contribute to fitness social dominance: hierarchy of social dominance hierarchy established through combative encounters relates to reproductive success females have less variation in reproductive success therefore dominance is less obvious in females sexual selection: courtship display or social dominance differential reproduction more important than differential survival many traits selected that benefit reproduction at a cost to survival attractiveness intra-sexual: same sex competition, usually males inter-sexual: one sex chooses mate, usually females females have more to lose Primates lemurs and loruses most ancestral great apes: hylobatidae (gibbons), ponginae (orangutans), hominae (gorillas, chimps, humans) chimps and Homo diverged ~7 MYA Homonid lineage larger brains, obligate bipedalism, smaller teeth Pan lineage larger teeth, facultative bipedalism, quadrupedalism Homonims achieved full bipedalism > 4 MYA started scavenging and used stone tools > 2.5 MYA starting hunting and fathering 1 MYA current large brains developed 0.2 MYA Homonid Lineage infer relation through fossil evidence times and locations of species existence known phylogenetic relationships inferred Australopiths existed 5-2 MYA several species divided among robust and lighter forms full bipedalism preceded large brains forest. vs savannah living unclear widespread across Africa Early Homo existed at the same time as at least two species of Australopithecus unclear which gave rise to later Homo Later Homo erectus and ergaster, larger brain species, emerged 1.8 MYA in Africa colonized much of Europe and Asia 800 000 YA the last common ancestor existed 200 000 YA in Africa modern humans arrive about 200 000 YA subsequent migration across globe and replacement of older farms Thinking about Human Evolution does not proceed in a singular line more extinct humans than surviving fewer than 1% of all known species are still in existence rapid evolution changes occur, triggered by sudden changes or environment or adaptive genetic mutations evolution does not necessarily result in perfect design not every trait is an adaption spandrels: incidental nonadaptive byproducts eg. belly button not all existing adaptive characteristics evolved to perform current function exaptations: evolved for one function but are now used for something else eg. bird wings originally for walking similarities among species do not necessarily point to a common origin homologous structure: similar structures, common origin eg. bat wing and human hand analogous structures: similar structure, no common origin eg. bee wing and bird wing result of convergent evolution: unrelated species adapting to same environmental demands Evolution of the Human Brain brain size generally correlated with body size but no simple relationship between the two exists size increase over evolution, mostly in cerebrum increased convolutions increase volume of cerebral cortex wrinkled due to convolution main ideas: brain is adapted to ancestral environment ie. better adapted to stone age than current ―big city‖ environment mind is modular: different modules respond to different selection pressures eg. language module vs. spatial module Human Mating Psychology most mammals form polygynous mating bonds humans generally form monogamous bonds may be adaptive in allowing more attention to survival of children aspects of human mate boding appear to be predicted by the evolutionary theory: men value indications of fertility women value power and earning capacity physical attractiveness predicts which women bond with men of high status men more likely than woman to commit adultery 2.3 FUNDAMENTAL GENETICS Mendelian Genetics Mendel studied dichotomous traits in true-breeding lines of pea plants dichotomous traits: occur in one form or the other, never in combination eg. brown seed OR white seed true-breeding lines: interbred members always produce offspring with the same trait dominant: appears in all first-gen offspring recessive: appears in 1/4 of second-gen offspring phenotype: observable traits genotype: traits present in the genes and can be passed off to offspring if dominant trait is present in genotype, it will be observed in the phenotype gene: inherited factors located on chromosomes in nucleus of each cell two genes controlling same trait: alleles homozygous: 2 identical alleles eg. BB, ww heterozygous: 2 different alleles eg. Bw Punnett Square R r R RR Rr r Rr rr Chromosomes and Replication humans have 23 pairs of chromosomes with an allele on each chromosome meiosis: process of cell division that has cells with 23 single chromosomes produces gametes, egg cells and sperm cells zygote: combined gametes (23+23) mitosis: process of cell division with daughter cells that have 23 pairs of chromosomes all other cell division chromosomes: DNA molecules, double strands of nucleotide bases wrapped around each other where genes are located nucleotides attract their complementary bases, making two DNA molecules identical to original Transcription and Translation DNA: double stranded molecule forming a chromosome AT-GC mechanism of gene expression replication: DNA strands unwind, nucleotide bases attract complementary bases -> 2 identical DNA molecules created mutations: errors in duplication transcription: mRNA synthesized from DNA mRNA leaves nucleus and attaches to ribosome in cell’s cytoplasm translation: ribosome synthesizes protein according to 3-base sequences (codons) of mRNA: UNIVERSAL GENETIC CODE Regulation of Gene Expression enhancers: DNA that determines whether genes initiate synthesis of proteins and at what rate (gene expression) determines development and function of a cell process of gene expression: transcription of DNA base-sequence code to RNA translation of RNA base-sequence code into amino acid sequence transcription factors: proteins that bind to a receptor, enter a cell and turns on genes one of two copies gets turned off epigenetics: the pattern of actual gene expression vs. genes possessed patterns of gene expression appear to be heritable Mitochondrial DNA mitochondria: structures that generate energy found in cytoplasm inherited from mother mutation of mitochondria related to disorders retraced maternal lineages to ―Mitochondrial Eve‖ revealed that homonids evolved in Africa and spread around the world Modern Genetics human genome project: mapped the 3 billion base sequences of human DNA we have only ~20 000 genes which means only a small proportion of chromosome segments have gene encoding regions active nongene DNA: influence gene expression microRNA: active in gene expression some genes produce more than one protein monoallelic expression (expression of only one allele of a gene) growing interest in epigenetics genes may interact and be silenced expression of genes (transcriptome and proteome) ≠ genome (gene expression) 2.4 INTERACTION OF GENETIC FACTORS AND EXPERIENCE Behavioral Development interaction of genetic factors and experience three influential studies: selective breeding of ―maze-bright‖ and ―maze-dull‖ rats (Cooper and Zubek) quantitative genetic trait performance on maze depended on rearing environment genotype ≠ phenotype phenylketonuria: a single-gene metabolic disorder (Folling) due to a single mutant recessive gene special diet during sensitive period of development lessens mental retardation example of interaction of genetics and environment development of birdsong (Thorpe and Marler) in two phases: sensory phase: begins several days after hatching sensorimotor phase: auditory feedback geographic variation in birdsong similar to human regional dialects gene/environment interaction produce and critique selves in anterior forebrain Quantitative Genetics study continuous traits (height, IQ) phenotype depends on effects of many genes different genes for different components of trait each gene sorts independently additive effect intermediate additive and subtractive effects of many genes F1 offspring exhibit intermediate trait 2.5 GENETICS OF HUMAN PSYCHOLOGICAL DIFFERENCES Genetics of Individual Differences Galton: twin studies dizygotic: fraternal monozygotic: identical identical twins reared apart more alike than fraternal twins heritability: proportion of variance that can be attributed to genetic variation differences between groups of people attributable to genetics multiplier effect: individuals seek out similar environments refer to populations not individuals cannot be generalized to populations from dissimilar environments Chapter 3- Anatomy of the Nervous System Chapter 3- Anatomy of the Nervous System 3.1 GENERAL LAYOUT OF NERVOUS SYSTEM Divisions of the Nervous System Central Nervous System (info processing centre) - brain (in skull) spinal cord (in spine) Peripheral Nervous Systerm - outside skull and spine - brings info to CNS (afferent) and signals from CNS (efferent) Somatic Nervous System - afferent nerves (sensory) - sensory signals from skin, skeletal muscles, joints, eyes, ears to CNS - efferent nerves (motor) - motor signals from CNS to skeletal muscles Autonomic Nervous System afferent nerves carry sensory signals from internal organs to CNS - efferent nerves - two stage neural paths, neuron exiting CNS synapses on a second-stage neuron before target organ - sympathetic nerves: project from CNS in lumbar (small of back) and thoracic (chest area) regions of spinal cord - ―fight or flight‖ - second stage neurons far from target organ - parasympathetic nerves: project from cranial and sacral (lower back) region of spinal cord - ―rest and restore‖ - second stage neurons near target organ 12 pairs of cranial nerves exit from brain sensory or sensory & motor many from head vagus nerves: longest cranial nerves MAIN POINTS: sympathetic nerves stimulate in threatening situations, parasympathetic nerves conserve energy (does not always hold) each autonomic target organ receives opposing sympathetic and parasympathetic input; activity controlled by relative levels or sympa/parasympathetic activities sympathetic changes indicative of psychological arousal, parasympathetic changes indicative of psychological relaxation Meninges, Ventricles, and Cerebrospinal Fluid - brain physically protected by: skull, meninges, CSF CNS covered by the three meninges (meninx): outermost meninx called dura mater (―tough mother‖) arachnoid membrane (web-like) subarachnoid space (contains large blood vessels and cerebrospinal fluid) innermost meninx called pia mater (―tender mother‖) cerebrospinal fluid (CSF) found in brain vesicles fills subarachnoid space supports and cushions brain produced by choroid plexuses (networks of capillaries) from pia mater excess continually absorbed into large blood filled spaces (dural sinuses) which run through dura mater and drain into large jugular veins of neck hydrocephalus: caused by blockage of CSF by tumor near narrow channels that link ventricles serves as conduit for some chemical messages central canal (small central channel) runs along spinal chord cerebral ventricles are the four large internal chambers of brain: lateral ventricles (2), third and fourth ventricle subarachnoid space, central canal and cerebral ventricles connected by series of openings- form a single reservoir Blood-Brain Barrier (chemical protection) Blood-Brain Barrier: tightly packed cells of blood vessel walls prevent entry of many molecules exists wherever there are blood vessels degree to which drugs influence brain activity depends on ease with which they penetrate this barrier large molecules critical for normal brain function (eg. glucose) transported through these walls blood vessel walls in some areas of brain allow certain large molecules to pass degree of permeability varied throughout body 3.2 CELLS OF THE NERVOUS SYSTEM Anatomy of Neurons Neurons: cells that receive, conduct and transmit electrochemical signals like any other cells except they can communicate amongst themselves - projections of external membranes 10 000 types of neurons, 3 categories motor (efferent) sensory (afferent) interneurons external anatomy: cell membrane: semipermeable membrane enclosing neuron dendrites: receive synaptic contact from other neurons axon hillock: where action potential is initiated axon: send info to other neurons cell body (soma): metabolic center of neuron myelin: fatty insulation around some axons: myelinated axon Nodes of Ranvier: gaps between sections of myelin buttons: endings of axon branches (which release chemicals into synapses synapses: connection between two different neurons - internal anatomy (cell soma): - endoplasmic reticulum: system of folded membranes - rough ER (with ribosomes): synthesis of proteins - smoother ER (without ribosomes): synthesis of fats - ribosomes: internal cellular structures on which proteins are synthesized - cytoplasm: clear internal fluid of cell - Golgi complex: membranes that package molecules in vesicles - nucleus: structure containing DNA - mitochondria: sites of aerobic (oxygen-consuming) energy release - microtubules: responsible for rapid transport of material throughout neurons - synaptic vesicles: spherical membrane packages that store neuro-transmitter molecules ready for release near synapses - neurotransmitters: molecules released from active neurons, influences activity of other cells - signaling proteins have domain outside of cell, a transmembrane domain and domain inside the cell - cause a change by binding on the outside domain (intercom system) - neuron cell membrane: composed of lipid bilayer - phospholipid bilayer embedded with protein molecules which are the basis of many cell functional properties - some are channel proteins through which certain molecules can pass - anything dissolvable in water cannot penetrate this layer - some are signal proteins which transfer a signal to inside of neuron when particular molecules bind to them on the outside of the membrane - classes of neurons: - multipolar neuron: more than two processes extending from cell body - most neurons - unipolar neuron: one process extending from cell body - bipolar neuron: two processes extending from cell body - interneuron: no distinct axon, unclear output - neuron that is neither sensory or motor regardless of shape - communicates between other neurons - integrate neural activity within a single brain structure (not to conduct signals from one structure to another) - neurons and neuroanatomical structure - two kinds: those composed primarily of cell bodies or axons - in CNS: clusters of cell bodies are called nuclei (nucleus) bundles axons called tracts - in PNS: clusters cell bodies are called ganglia (ganglion) bundles axons called nerves Glial Cells - specialized to support neurons (―ground crew‖) Oligodendrocytes: produce myelinated wrappings around axons extensions rich in myelin (fatty insulating substance) myelin sheaths formed increase speed and efficiency of axonal conduction several myelin segments Schwann cells: glial cells in PNS one myelin segment can guide axonal regeneration after damage Microglia: smallest glia respond to injury or disease by multiplying, engulfing cellular debris and triggering inflammatory responses to recruit other aspects of immune system Astrocytes: largest, star-shaped support projections and connections between neurons modulate cell signaling extensions cover outer surfaces of blood vessels in the brain make contact with neuron cell bodies - allows and blocks passage of certain chemicals from blood into CNS neurons - send and receive signals from neurons and other glial cells - control establishment and maintenance of synapses between neurons - modulate neural activity TERMINOLOGY CNS PNS Myelin-providing Oligodendrocyte Schwann cells glia s Clusters of cell Nuclei (nucleus) Ganglia (ganglion) bodies Bundles of axons Tracts Nerves 3.3 NEUROANATOMICAL TECHNIQUES AND DIRECTIONS Neuroanatomical Techniques golgi stain: silver chromate stains neurons to show ultrastructure of cells - discovered by Camillo Golgi nissl stain: cresyl violet or thiamin binds only to neuron cell bodies (ribosomes) used to estimate number of cell bodies in an area discovered by Franz Nissl electron microscopy: coat neural tissue with electron-absorbing substance which is absorbed to different degrees by different parts of the neuron creates a electron micrograph which captures neuronal structure scanning electron microscopy provides 3D image uses reflection transmission electron microscopy provides 2D image (slice-through) con: hard to visualize general aspects of neuroanatomical structure neuroanatomical tracing techniques (tract tracing): anterograde (going forward): chemical travels through microtubules to synapses retrograde (going back): taken into synaptic terminals and stains cell body usage: build maps of neural circuits Directions in the Vertebrate Nervous System described in relation to orientation of spinal cord three axes: anterior-posterior, dorsal-ventral, medial-lateral (in terms of animals on four limbs) anterior (cranial/rostral): toward the nose end posterior (caudal): toward the tail end dorsal: toward the surface of back ventral: toward the floor medial: toward midline of body lateral: away from midline superior (above): top of primate head inferior (below): bottom of primate head proximal: ―close‖-r to CNS distal: ―far‖-ther from CNS - anatomical planes of section: - horizontal - frontal (coronal) - sagittal - midsagittal: section between two hemispheres - cross section: a section cut at a right angle to any large, narrow structure 3.4 SPINAL CORD - composed of: gray matter composed of cell bodies and unmyelinated interneurons two dorsal arms, dorsal horns (afferent-sensory) two ventral arms, ventral horns (efferent-motor) white matter info up to and down from brain surrounding matter composed of myelinated axons (very fatty) this myelin gives it the white appearance spinal nerves: attached to either side of spinal cord at 31 different levels of the spine axons joined to cord via dorsal root: afferent unipolar neurons with cell bodies grouped together: dorsal root ganglia synaptic terminals in dorsal horns - axons joined to cord via ventral root: - efferent multipolar neurons with cell bodies in ventral horns - somatic project to skeletal - autonomic project to ganglia, synapse on neurons which project to internal organs 3.5 FIVE MAJOR DIVISIONS OF THE BRAIN Hindbrain Myelencephalon (medulla oblongata) composed largely of tracts which carry signals between rest of brain and body basic bodily functions (heart rate, breathing, vomiting, blood pressure) location of reticular formation (―little net‖) central core of brain stem controls arousal and sleep Metencephalon many tracts part of reticular formation pons, on brain stem’s ventral surface cerebellum (―little brain‖), on dorsal surface controls coordination and some cognitive function Midbrain Mesencephalon cerebral aqueduct: connects third and fourth ventricles tectum (roof), dorsal surface of midbrain inferior colliculi: auditory function superior colliculi: visual function tegmentum: ventral to tectum pariaqueductal gray: pain perception mediates pain-reducing effects of opiate drugs substantia nigra: role in Parkinson’s red nucleus: role in movement Forebrain Diencephalon: composed of thalamus and hypothalamus thalamus: relays incoming sensory info white lamina (layers) composed of myelinated axons on surface massa intermedia: joins thalamus lobes together sensory relay nuclei: thalamic nuclei which receive and transmit sensory info lateral geniculate: visual station medial geniculate: auditory station ventral posterior: somatosensory station hypothalamus (―below thalamus‖): regulation of motivated behaviors regulates release of hormones from pituitary gland (―snot gland‖) Telencephalon: controls brain’s most important functions voluntary movements, sensory input, cognitive processes Structures of the Brain Cerebral Cortex (neocortex): tissue covering cerebral hemispheres cortex (―bark‖): 3 mm thick, 1600 cm^2 white matter: axons, white because of myelin grey matter: cell bodies and dendrites longitudinal fissure: groove separating right and left hemispheres largest commissure: corpus callosum: connects hemispheres convoluted in humans, most animals lissencephalic (smooth-brained) large convolutions called fissures small convolutions called sulci ridges between fissures and sulci called gyri Cortical Layers six-layered cortex of recent evolution grey to white matter, I-VI vary in thickness columnar organization: vertical flow of information Lobes frontal: motor functions and higher cognitive processes parietal: sensation and perception temporal: hearing and language, complex visual patterns, certain memories occipital: visual input hippocampus: major role in memory, especially spatial location not neocortex, only has 3 major layers medial edge of cerebral cortex, folds into seahorse shape Subcortical Structures (archicortex): consists of: limbic system: regulation of motivated behaviors ie. fleeing, feeding, fighting, sexual behavior consists of five major structures: amygdala: emotion processing, especially fear cingulate cortex: largest strip of cortex in cingulate gyrus fornix: major tract septum: midline nucleus basal ganglia: coordinated voluntary motor responses amygdala cingulate cortex septum Chapter 4 - Neural Conduction and Synaptic Transmission dendrites: receive input from sensory cells many dendrites per neuron cell body: integrates flow of information axon hillock integrates input, decides whether or not to transmit info excitatory or inhibitory axon: transmits signal one axon per neuron Structure Indicates Function sensory relays info not many dendrites interneurons process info motor neurons control behavioral output talks to a muscle fibre - transmission of neurons electrical and chemical 4.1 RESTING MEMBRANE POTENTIAL cell membrane: divides inside from outside selectively permeable intracellular: negative proteins extracellular membrane potential: difference in electrical charge between the inside and the outside of a cell inside of neuron -, outside of neuron + resting potential: -70 mV polarized cell: -70 mV charge across membrane cell key ions: Na+, K+, Cl- and various negatively charged protein ions greater concentration Na+ and Cl- outside greater concentration K+ and protein ions inside proteins do not move and are synthesized within the neuron Ionic Basis of the Resting Potential resting neurons polarized due to ions: positively or negatively charged particles two distribute ions evenly: random motion: move from high concentration -> low concentration electrostatic pressure: attraction of like and repulsion of opposite charges two factors contributing to uneven distributions: selective permeability to certain ions passive: no consumption of energy K+ and Cl- pass easily, Na+ barely and proteins are trapped inside sodium-potassium pumps counteract random motion active: consumes energy exchanges 3 Na+ inside for 2 K+ outside closed at resting potential Equilibrium Potential Hodgkin-Huxley Model: potential an ion will move to achieve when allowed to move freely: Na+ = 120 mV driven into cell by both electrostatic pressure and random motion K+ = 90 mV driven into cell by electrostatic pressure and out by random motion Cl- = -70 mV 4.2 GENERATION AND CONDUCTION OF POSTSYNAPTIC POTENTIALS - neurons can use and change potentials neurotransmitters bind at postsynaptic receptors causes electrical changes by: depolarizing: bringing -70 mV closer to 0 (decreasing resting membrane potential) EPSP hyperpolarizing: making -70 mV more negative (increasing resting membrane potential) IPSP membrane potential finely balanced (egg on edge of table) IPSP pushes back EPSP pushes forward chain reaction if enough EPSP EPSPs and IPSPs - travel passively - graded responses: weak signals = small postsynaptic potentials, strong = large potentials EPSPs (excitatory) increase likelihood that neuron will fire IPSPs (inhibitory) decrease likelihood that neuron will fire - travel very quickly and are decremental (fade as they travel) 4.3 INTEGRATION OF PSPs AND GENERATION OF ACTION POTENTIALS action potentials generated near axon hillock threshold of excitation: about -65 mV depolarizes membrane when reached integration: adding or combining individual signals into one overall signal spatial summation: integration of events happening at different places temporal summation: integration of events happening at different times 4.4 CONDUCTION OF ACTION POTENTIALS action potential: reversal of membrane potential from ~-70 mV to ~50 mV all-or-none response: either occurs to full extent or not at all voltage-activated ion channels: ion channels that respond to changes in level of membrane potential open when threshold is reached once cell is sufficiently depolarized, sodium channels open up Na+ rushes into cell -> change in membrane potential a single action potential has little effect on relative concentrations of various ions inside and outside neuron resting ion concentrations next to membrane reestablished by random movement of ions Refractory Periods absolute refractory period: impossible to initiate another action potential relative refractory period: harder to fire neuron again responsible for two important characteristics of neural activity: action potentials travel in one direction portions of axon over which an action potential has just travelled are left momentarily refractory limits rate of firing at a high level of continual stimulation: fires continuously until absolute refractory period is over if stimulation is just sufficient to fire neuron when at rest: neuron does not fire until both absolute and relative refractory periods are over intermediate levels of stimulation: intermediate rates of neural firing PSPs vs. Action Potentials EPSPs/IPSPs Action Potentials
 • Decremental • Nondecremental • Fast • Conducted more slowly than PSPs Passive (energy is not used) • Passive and active (use ATP) Axonal Conduction of Action Potentials one-way due to refractory period slower than PSPs AP depolarizes neighboring region of axon to trigger continued movement of action potential mouse-trap analogy: energy stored by striker against pressure of spring = energy stored by sodium channels by holding back Na+ ions vibration signaled by first activated trap transmits passively down the shelf until all traps are sprung = nondecremental nature of action potential conduction trap cannot respond again until reset = refractory period, axon cannot fire again until repolarized row of traps can transmit in either direction = axon Conduction in Myelinated Axons passive conduction, instantly and decrementally, along segments of myelin to node of Ranvier open voltage-activated sodium channels and generate new action potential at each node myelination increases speed of axonal conduction saltatory conduction: transmission of action potentials in myelinated axons signal jumps along axon from node to node at 120m/s The Velocity of Axonal Conduction depends on two properties: diameter of axons the larger, the faster fast in motor neurons: 60m/s in humans myelination Conduction in Neurons without Axons conduction in interneurons passive and decremental The Hodgkin-Huxley Model in Perspective based on squid neurons cannot be fully applied to the cerebral neurons as they have different properties such as: fire continually even without input baseline firing rate some axons can conduct both graded signals and action potentials action potentials of different types vary in duration and amplitude many cerebral neurons have no axons and do not display action potentials some cerebral dendrites can conduct action potentials 4.5 SYNAPTIC TRANSMISSION: CHEMICAL TRANSMISSION OF SIGNALS AMONG NEURONS Structure of Synapses axodendritic synapses: axons synapse onto dendritic spines dendritic spines: nodules located on surfaces of dendrites axoaxonic synapses: mediate presynaptic facilitation and inhibition selectively influence one particular synapse directed synapses: synapses at which the site of neurotransmitter release and site of neurotransmitter reception are close together non-directed synapses: synapses at which the site of release is far from site of reception Release of Neurotransmitter Molecules exocytosis: process of neurotransmitter release depends on Ca2+ channel activity stimulation of action potential at terminal opens voltage-activated calcium channels entry of Ca2+ causes vesicles to fuse with terminal membrane and release contents Activation of Receptors by Neurotransmitter Molecules released NT molecules produce signals in postsynaptic neurons by binding to receptors receptors are specific for a particular NTs NTs can only influence the cells that have receptors for it ligand: a molecule that binds to another a NT is a ligand of its receptor Receptor Subtypes there are multiple receptor types for a given NT since different types of receptors respond to NTs in different ways, one NT can transmit different messages to different parts of brain ionotropic: causes changes in postsynaptic membrane by opening ion channel NT binds and an associated ion channel either opens or closes, causing a PSP EPSPs occur due to increased flow of Na+ into neuron IPSPs occur due to increased flow of K+ ions out of and Cl- ions into neuron happens quickly act directly on ion channels metabotropic: depends on receptors on postsynaptic membrane NT 1st messenger binds G protein subunit breaks away ion channel is opened/closed OR a 2nd messenger is synthesized 2nd messengers may have a wide variety of effects slow, long lasting effects attached to portion of signal protein outside neuron G protein attached to portion of signal protein inside neuron Reuptake, Enzymatic Degradation and Recycling as long as the NT is in the synapse, it is active; the activity must somehow be turned off reuptake: once released, almost immediately scooped back into presynaptic buttons and recycled more common enzymatic degradation: degradation via enzymes Glial Function and Synaptic Transmission astrocytes appear to communicate and modulate neuronal activity modulation through glial cells: glia release chemicals within self or modulate synapse, respond to neurotransmitters some release transmitters, contain receptors, conduct signals, and modulate NT reuptake Gap Junctions (electrical synapse) gap junctions: connection between adjacent cells triggered by Na+ contiguous cytoplasm conducts electric potential changes more common in invertebrates fast communication permits communication in either direction 4.6 NEUROTRANSMITTERS Amino Acids - found at fast-acting directed synapses in CNS glutamate: most prevalent excitatory NT in CNS GABA: synthesized from glutamate most prevalent inhibitory NT in CNS inhibitory, hyperpolarizes aspartate and glycine Monoamines synthesized from single amino acids effects tend to be diffused neuromodulator: a chemical that modulates neural activity more diffuse than directed synapse catecholamines: synthesized by amino acid tyrosine dopamine (made by preexisting amino acids) epinephrine (made by preexisting amino acids) nonepinephrine - indolamines: synthesized from tryptophan serotonin Acetylcholine own group of Acetyl + choline first identified at neuromuscular junction released from motor neuron binds to muscle neuron to trigger muscle contraction Unconventional Neurotransmitters soluble gases: exist only briefly local, rapid actions important for backwards communication nitric oxide carbon monoxide retrograde transmission: backwards communication regulate activity of presynaptic neurons endocannabinoids: similar to THC (marijuana) anandaminde produced immediately before release have effect on presynaptic neuron Neuropeptides produced through gene transcription large molecules eg. endorphins produce analgesia (pain suppression) receptors identified before natural ligand 4.7 PHARMACOLOGY OF SYNAPTIC TRANSMISSION AND BEHAVIOR agonists: facilitate effects of an NT antagonist: inhibit effects of an NT jams receptors eg. SSRI: inhibit selective reuptake by serotonin, more available to act at postsynaptic cells How Drugs Influence Synaptic Transmission may alter NT activity at any point of its life cycle receptor blockers: bind to postsynaptic receptors without activating them block access of usual NT eg. curare: blocks neurotransmission at neuromuscular junctions, paralyzing effect 7 general steps: synthesis of NT storage in vesicles break-down in cytoplasm of leaky NTs from vesicles exocytosis inhibitory feedback via autoreceptors activation of postsynaptic receptors deactivation 7.1 ORGANIZATION OF SENSORY CORTEX primary sensory cortex receive input from thalamus secondary sensory cortex receive input mostly from primary and other parts of secondary cortex association cortex receive input from multiple sensory systems mostly from secondary sensory cortex Hierarchical Organization specificity and complexity of processing increases with each level sensation: detecting a stimulus perception: understanding the stimulus Functional Segregation functional segregation: distinct functional areas within a level different areas process different kinds of information eg. edges, color, form Parallel Processing parallel processing: different information from different streams processed simultaneously Binding Problem hierarchical, segregated, parallel processing processes sensory and perceptual info how does the brain combine this info for a unitary perception? grandmother cell? maybe there is no binding perception may be distributed in the system some systems do have cells with highly selective responses to complex stimuli, however Mirror Neuron - mirror neuron: a neuron that fires either when x stimulus is produced or perceived Chapter 5 - Research Methods of Biopsychology PART I: Methods of Studying the Nervous System 5.1 METHODS OF VISUALIZING AND STIMULATING THE BRAIN contrast x-rays: inject a substance (contrasting agent) which absorbs x- rays either more or less than surrounding tissue cerebral angiography: infuse radio-opaque dye into cerebral artery to visualize cerebral circulatory system during x-ray photography used in locating vascular damage, sometimes tumors x-ray computed tomography (CT): computer assisted x-ray procedure (like a 3D scanner) requires contrasting agent (intravenous delivery) magnetic resonance imaging (MRI): measures waves emitted by hydrogen atoms when activated by radio-frequency waves in a magnetic field high resolution 2D & 3D images high spatial resolution: ability to detect/represent differences in location of parts of the brain 1.5-10 Tesla (magnet) no contrasting agent necessary positron emission tomography (PET): provides images of brain activity radiolabeled substance (2DG) is injected into carotid artery taken up by cells and accumulates since it cannot be metabolized each scan is an image of the levels of radioactivity in various parts of one horizontal level of the brain eg. A PET scan of a subject reading after a 2DG injection reveals the most active levels of brain during this activity low spatial resolution functional MRI (fMRI): increase in oxygen flow in brain produces images of brain activity (BOLD signal) and structure imaged using waves emitted by hydrogen atoms uses strong magnetic field like MRI greater info can be gathered by using MRI then fMRI- greater spatial resolution no radiation injection necessary lower resolution than MRI magnetoencephalography (MEG): measures changes in magnetic fields on surface of scalp created by underlying patterns of neural activity fast temporal resolution transcranial magnetic stimulation (TMS): applies a brief, strong magnetic field to alter neural activity can either activate or deactivate brain structures to observe changes in behavior not a measurement of neural activity 5.2 RECORDING HUMAN PSYCHOPHYSIOLOGICAL ACTIVITY scalp electroencephalography (EEG): measures gross electrical activity in the brain uses electrodes attached to the scalp techniques of EEG: wave form assessment: indication of state of consciousness, pathology alpha waves, associated with relaxed wakefulness event-related potentials (ERPs): measure activity accompanying psychological events combination of EEG with MRI electromyography: measure of muscles tension under the skin measured using electromyogram (EMG) which measures electrical activity of muscles electrooculography: recording eye movements electrooculogram (EOG) records eye movements by measuring changes in electrical potential between front and back of eyeball skin conductance: measures of electrodermal activity measures skin conductance level (SCL) and skin conductance response (SCR) cardiovascular activity: measures heart rate, blood pressure and volume physiological changes differ with emotional state 5.3 INVASIVE PHYSIOLOGICAL RESEARCH METHODS Stereotaxic Surgery no pain receptors in brain requires use of stereotaxic atlas and instruments for precise location may be used to manipulate tissue, implant electrodes or cannulae Lesions powerful experimental tool whose results must be interpreted carefully cannot tell you what a brain region is for: tells you what an organism cannot do without that brain region can be used to remove, damage, or inactivate a structure Lesion Methods bilateral and unilateral lesions mostly bilateral several procedures each requiring careful interpretation of effects aspiration lesions: to access eyes radio-frequency lesions: heat from current destroys tissue knife cuts: eliminates conduction in a nerve cyrogenic blockade (cooling): reversible lesions Electrical Stimulation may be used to ―activate‖ a structure stimulation of a structure may have an effect opposite the observed when structure is lesioned Invasive Electrophysiological Recording Methods on non-human subjects intracellular unit recording: reports membrane potential of a neuron can detect action potential extracellular unit recording: reports firing of a neuron cannot detect action potential multiple-unit recording: reports firing of many neurons invasive EEG recording: measures cortex directly, not just scalp 5.4 PHARMACOLOGICAL RESEARCH METHODS agonists: drug mimics facilitates endogenous compound antagonists: drug inhibits blocks endogenous compound delivery acute (one time) or chronic (days, weeks, months...) Routes of Drug Administration fed or injected cannula: a fine hollow tube stereotaxically implanted into brain to overcome blood-brain barrier Selective Chemical Lesions some compounds may selectively damage target brain regions neurotoxins (neural poisons) eg. kainic acid and ibotenic acid kill cell bodies near injection but spare passing-by axons some drugs only taken up by particular neurons Pharmacological Methods use of drugs to manipulate the brain drugs may target selective neural systems more accurately than surgical techniques depending on drug specificity delivery methods: acute vs. chronic oral dose vs. infusion into stomach injection infusion into brain ventricles or brain tissue via cannula time release implants Measuring Chemical Activity of the Brain 2-DG technique: uses a glucose analog that cannot be metabolized observe animal after injection of 2-DG use autoradiography to see where radioactivity accumulates in brain slices - cerebral dialysis: measures extracellular concentration of specific chemicals insert fine tube with semi-permeable membrane, extracellular fluid collected for later analysis Locating Neurotransmitters and Receptors in the Brain immunocytochemistry: based on specific antibodies to label dye or radioactive labels used to visualize the molecules of interest a receptor based on immune response reacting to remove or destroy antigens (foreign proteins); tracks labeled antibodies also called immunohistochemistry in situ hybridization: uses labeled RNA to locate neurons with complementary mRNA Immediate-early Genes genes that produce transcription factors, control expression of other genes eg. egr-1, c-fos, etc. many are produced in neurons following repeated depolarization end-products include molecules that may change long-term connectivity can be used as a marker of neural activity following a stimulus or activity protein labeled with immunocytochemistry, RNA labeled with in situ hybridization 5.5 GENETIC ENGINEERING Gene Knockout Techniques subjects missing a given gene can provide insight into what the gene controls difficult to interpret results: most behavior is controlled by many genes and removing one may alter the expression of others antisense drugs block expression of a gene Gene Replacement Techniques insert pathological human genes in mice PART II: Behavioural Research Methods of Biopsychology 5.6 NEUROPSYCHOLOGICAL TESTING time consuming therefore only conducted on those with brain damage used to diagnose neural disorders serves as a basis for counseling/caring for patients provides information on effectiveness and side effects of treatment Progression of Neuropsychological Testing single-test approach goal: to differentiate brain damage from psychological causes failed standardized-test-battery approach same goal as single test approach: identify brain-damaged patients eg. Halstead-Reitan battery aggregate scores (sum) used to characterize patients poor at discriminating nature of performance on task; neurological patients from psychiatric patients customized-test-battery approach now predominant common-test-battery tests followed-up by customized tests according to results characterizes nature of psychological deficits Tests of the Common Neuropsychological Test Battery intelligence WAIS memory digit-span subtest: longest sequence of correctly repeated digits language- problems of phonology, syntax or semantics language lateralization- used to identify language-dominant hemisphere sodium amytal test: anesthetize one hemisphere dichotic listening: ear contralateral to dominant hemisphere shows superior hearing ability Tests of Specific Neuropsychological Function memory: explore nature of deficits short-term, long-term, both? anterograde or retrograde? semantic or episodic? explicit or implicit? language: explore problems of phonology, syntax or semantics Frontal Lobe Function Wisconsin card sorting task patients with frontal lobe damage may be impaired in switching strategy perseverate on previous sorting strategy 5.7 BEHAVIOURAL RESEARCH METHODS OF BIOPSYCHOLOGY assumptions: complex processes are a result of combined simple cognitive processes (constituent cognitive processes) each complex cognitive process is mediated by neural activity in a particular area of the brain goal is to identify the parts of the brain that mediate various constituent cognitive processes paired-image subtraction technique: compare PET or fMRI images during several different cognitive tasks important technique in neuroimaging eg. subtract activity observed when viewing a scrambled image vs. viewing image infer activity related to perception of the object 5.8 BIOPSYCHOLOGICAL PARADIGMS OF ANIMAL BEHAVIOR Animal Behaviour Methods procedures developed for the investigation of a particular behavioural phenomenon assessment of species-common behaviors: open-field test measures anxiety levels tests of aggressive and defensive behavior tests of sexual behavior Traditional Conditioning Paradigms Pavlovian conditioning pairing an unconditioned stimulus with a conditioned stimulus operant conditioning reinforcement and punishment conditioned taste aversion delayed consequence still led to association in one trial self-stimulation animal works for electrical stimulation to pleasure centers Seminatural Animal Learning Paradigms conditioned taste aversion pairing something that makes an animal emetic (ill) with a taste animals appear prepared to associate tastes and illness challenged existing assumptions about conditioning radial arm maze goal: eat food in the arms of the maze demonstrated spatial learning can measure working memory and reference (long-term) memory Morris water maze goal: find platform in murky water demonstrated spatial memory and learned strategies results must always be interpreted carefully what is measured? performance? acquisition time? what components contribute to completion of behavior? motivation, learning, motor performance, perception, et cetera Chapter 6 - The Visual System 6.1 LIGHT IN THE EYE light: photons or waves waves of electromagnetic energy properties of light: wavelength and intensity wavelength: color intensity: brightness Vision our perceptual systems create a representation of the world, not what the world is actually like we see wavelengths of light that bounce off objects as color: color does not exist we represent the world in a way that is useful to us visual system is a product of evolution many things give off wavelengths but we can only detect part of it: visible light most insects and birds see into the UV range pit vipers detect infrared radiation Light properties of particles and of waves we interpret wave length (color) and intensity (brightness) Eyes evolved via cumulative changes with several flaws: blind spot and backwards retina we have a lens eye transduction: to convert light to neural signals The Pupil and the Lens iris controls amount of light reaching retina pupil adjusts according to sensitivity: ability to see in dim light, and acuity: ability to detect details of an object contracted pupils have higher acuity lens: focuses incoming light on the retina ciliary muscles: adjusts tension when we are looking near or far accommodation: configuration of lens to focus images, by ciliary muscles may also provide depth information Eye Position and Binocular Disparity convergence: the eyes turn inward to focus on nearer objects binocular disparity: difference of position of objects between the two eyes both greater when objects are close provides brain with a 3D image and distance information 6.2 TRANSDUCTION IN THE RETINA retina is composed of 5 layers of different types of neurons: receptors horizontal cells: specialized for communication across major channels of sensory input bipolar cells amacrine cells: specialized for communication across major channels of sensory input retinal ganglion cells: communicate chemically and electrically the retina is inside-out tapetum lucidum: reflective layer at back of retina doubling chances of photon hitting a photoreceptive cell present in some animals light passes through several cell layers before reaching its receptors: receptors -> bipolar cells -> retinal ganglion cells fovea: highest resolution vision in centre of retina high concentration of photoreceptors and increased sensitivity ganglion cell layer thinner here to reduce distortion of light blind spot: no photoreceptors where info exits the eye completion: filling in the blind spot Cone and Rod Vision rods: detects light scotopic vision (nighttime) more common in peripheral area common in nocturnal species lacks detail more convergence: rods project to same ganglion cell cones: detects color photopic vision (daylight) only at fovea common in diurnal species (daylight creatures) projects to own ganglion cell duplexity theory of vision: cones and rods mediate different kinds of vision Spectral Sensitivity lights of the same intensity but different wavelengths may not all look as bright rods and cones respond differently to different wavelengths of light spectral sensitivity curve: shows relationship between wavelength and brightness different for photopic and scotopic vision Purkinje effect: spectral sensitivity shifts as light decreases ie. blues perceived as more intense in dimmer light Eye Movement saccades: the quick and jerky eye movements we use to scan the world temporal integration: images integrated over time see nothing if stabilize retinal image; visual system responds to change visual transduction: depends on reactive photopigments ie. rhodopsin: a pigment found in rods responds to light rather than to neurotransmitters in the dark, Na+ channels open and glutamate is released in light, Na+ channels close, rods hyperpolarize, inhibit glutamate signals often transmitted through inhibition 6.3 RETINA TO PRIMARY VISUAL CORTEX retina-geniculate-striate pathway: projects to primary visual cortex (striate cortex) via lateral geniculate nuclei (located in thalamus) each side sends info to both sides of the brain each lateral geniculate has 6 layers each layer receives input from all parts of contralateral visual field of one eye 3 layers left, 3 layers right Retinotopic Organization retinotopic: info received at adjacent portions of retina remains adjacent in striate cortex more cortex devoted to areas of high acuity 25% of primary visual cortex dedicated to input from the fovea The M and P Channels magnocellular layers: bottom two layers of lateral geniculate nuclei (LGN) big cell bodies responsive to movement input from rods parvocellular layers: top four layers of LGN small cell bodies responsive to color, detail, still or slow objects input from cones project to different sites in lower part of layer IV in striate cortex M and P portions of lower layer IV project to different parts of visual cortex 6.4 SEEING EDGES edges define extent and position of objects and scenes visual systems excellent at detecting and representing edges via contrast enhancement through lateral inhibition: when a receptor fires, it inhibits its neighbors laterally across receptors Mach bands: enhance contrast at edges Visual Receptive Fields the area within which it is a visual stimulus can influence the firing of a neuron some respond to lines, particular angles, monocularly, binocularly, etc. cells with simple receptive fields project to those with complex receptive fields Hubel and Wiesel studied retinal ganglion, LGN and lower layer IV of striate cortex similarities at the three levels: receptive fields of foveal areas are smaller than those in the periphery neurons’ receptive fields are circular in shape neurons are monocular: receptive field in one eye but not the other many neurons at each level have receptive fields with excitatory and inhibitory area many cells have receptive fields with a center-surround organization: excitatory and inhibitory regions some ―on-center‖ some ―off-center‖ responds to light in center or periphery, respectively Receptive Fields: Simple and Complex Cortical Cells in lower layer IV of striate cortex: neurons with circular receptive fields are rare neurons are either: simple: divisible ―on‖ and ―off‖ regions complex: larger receptive fields, impossible to divide ―on‖ ―off‖ regions respond to line orientation regardless of position Columnar Organization of Primary Visual Cortex cells with simpler receptive fields send info to cells with complex receptive fields all cells in a functional vertical column have same receptor field and ocular dominance ocular dominance columns: dominance changes as you move horizontally (alternating L-dominance and R-dominance) retinotopic organization maintained 6.5 SEEING COLOR component theory (trichromatic theory): 3 types of receptors each with a different spectral sensitivity proposed by Young, refined by Helmholtz some species have 3 cone types but different spectral tuning some species have 4+ types explains coding of color by cones opponent processing theory: two different classes of cells encode color, another class encodes brightness proposed by Hering based on complementary colors seen on all subsequent levels Color Constancy and the Retinex Theory color constancy: color perception is not altered by varying wavelengths visual systems adjust to lighting to give same colors retinex theory: color is determined by proportion of light of different wavelengths a surface reflects perception of color due to relative wavelengths rather than absolute wavelengths dual-opponent cells sensitive to color contrast found in cortical ―blobs‖ 6.6 CORTICAL MECHANISMS OF VISION AND CONSCIOUS AWARENESS flow of visual information: thalamic relays neurons to 1 visual cortex (striate) to 2 visual cortex (prestriate) to visual association cortex as visual info flows through hierarchy, receptive fields become larger and respond to more complex and specific stimuli Damage to Primary Visual Cortex scotomas: areas of blindness in contralateral visual field due to damage to primary visual cortex detected by perimetry test people with this disorder usually unaware due to completion blindsight: perception of stimuli outside of conscious awareness islands of functional cells mediate visual abilities direct connections between subcortical structures and secondary visual cortex not available to conscious awareness Functional Areas of Secondary and Association Visual Cortex neurons in each area respond to different visual cues (color, movement, shape) lesions of each area results in specific deficits anatomically distinct around 12 functionally distinct areas identified so far retinotopically organized Dorsal and Ventral Streams dorsal: pathway from primary visual cortex to dorsal prestriate cortex to parietal cortex the ―where‖ pathway (location and movement) pathway for control visually of behaviour ventral: pathway from primary visual cortex to ventral prestriate cortex to inferotemporal cortex the ―what‖ pathway (color, form and shape) pathway for conscious perception of objects Prosopagnosia prosopagnosia: inability to distinguish among faces associated with damage to ventral stream between occipital and temporal lobes may be able to recognize faces without conscious awareness patients have different skin conductance responses to familiar faces compared to unfamiliar faces even they do not recognize them Akinetopsia akinetopsia: deficits in movement perception can be induced by high dose of antidepressants associated with damage to middle temporal area of cortex 7.2 HEARING Auditory System create perception of objects/events by sound they make sounds are vibrations in a medium: air, water, solids Sound Waves vibrations generated by motion compressions of the air amplitude: loudness frequency: pitch respond to certain wavelenghts: 20Hz-20kHz timbre: sound quality eg. violin vs. tuba Fourier analysis: complex waves are combinations of simple waves Pitch Perception related to fundamental frequencies of a sound low fundamental frequency = low pitch we perceive missing fundamental frequencies eg. over the telephone The Ear sound wave -> eardrum -> ossicles -> oval window -> Cochlea fluid transduction takes place in organ of Corti (cochlea’s internal membrane) composed of basilar membrane (hair cells and auditory receptors) and tectorial membrane stimulation of basilar membrane triggers APs in auditory nerve Place Theory different frequencies produce different waves along organ of Corti high stimulations stimulate closer hair cells, low frequencies stimulate hair cells further in tonotopic (frequency based) organization of basilar membrane for high frequency sounds Temporal Theory rate of neurons firing encodes frequency rate of firing matches with rate of vibration problem: neurons can only fire so fast limited by refractory periods works for low frequency sounds Theories of Frequency Transduction volley theory: in combination, many neurons could encode frequency through combined firing rates eg. rows of gun shooters From the Ear to the Primary Auditory Cortex ipsilateral (same side) axons of auditory nerve synapse projection to both sides of brain stem after first projection into CNS axons project from inferior colliculi to medial geniculate nuclei of thalamus thalamic neurons project to primary auditory cortex Sound Localization interaural time differences arrival time delay phase delay interaural intensity differences spectral differences due to pinna; sounds depend on how they bounce off Subcortical Mechanisms of Sound Localization medial: arrival time differences lateral: amplitude differences medial and lateral parts project to superior colliculus topographic representation of location of sound according to auditory space cells within superior colliculus match where the sound comes from in the space around you Interaural Timing Difference coincidence detectors: the cell that will respond if it is getting two inputs at the same time built in below cortex - detect where sounds are coming from quicker than identifying what the sound is Ch 9 - Development of the Nervous System neural development consists of a series of processes continue into adulthood and result in neural processes highest rates earlier in development and through childhood/puberty nervous system more susceptible to environment during early development also more plastic: greater chance of recovery depends critically on sensory input: ―sensitive‖ or ―critical‖ period eg. Genie; development of ocular dominance 9.1 PHASES OF NEURODEVELOPMENT induction of neural plate formation of neural tube neural proliferation migration and aggregation axon and dendrite growth (overproduction) synapse formation (overproduction) neuron death and synapse rearrangement (pruning) Induction of Neural Plate patch of tissue on dorsal surface of embryo becomes neural plate mesoderm layer controls development by inducing by chemical signals visible 3 weeks after conception 3 layers of embryonic cells: ecto, meso, endo neural plate cells: embryonic stem cells unlimited capacity for self renewal can become any kind of cell totipotent: earliest cells, ability to become any cell multipotent: with development, limited to becoming certain cells Neural Tube becomes the CNS failure of tube to fully close can result in defects cells created in ventricular zone of neural tube Neural Proliferation neural plate → neural groove → neural tube inside will be the cerebral ventricles and neural tube neural tube cells proliferate (multiply greatly) in species-specific ways: 3 swellings at anterior end in human brains → forebrain, midbrain, hindbrain proliferation chemically guided by organizer areas: roof plate & floor plate Neural Migration once cells have been created, they migrate migrating cells do not have dendrites or axons two types of neural tube migration: radical: moving out usually along radial glial cells tangential: moving up two method
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