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Module 2(Wk 7-12) Notes.docx

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McGill University
PSYC 100
Ingrid Johnsrude

Week 7: Chapter 4: Brain and Behaviour Nervous System - structure  central nervous system o brain and spinal cord  peripheral nervous system o nerves=bundles of fibres that transmit info between CNS and the rest of body o cranial nerves= carries sensory info from head and neck regions (ex. vision, hearing, eye movements) o spinal nerves= carries sensory info from rest of body  3 major parts of the brain o brain stem (most primitive region; incudes medulla, pons, midbrain) o cerebellum (attached to back of brain stem; controls and coordinates movements) o cerebral hemispheres (largest part of brain; parts of brain the evolved most recently)  brain and spinal cord protected by meninges o 3 layered set of membranes o dura matter, arachnoid membrane, pia matter  brain and spinal cord float in cerebrospinal fluid (CSF) o fills space between two meninges o provides a shock-absorbing cushion  brain’s capillaries do not have openings o blood-brain barrier= prevents some substances from passing from blood into brain  arteries carry fresh blood to the brain  veins and sinuses carry used blood away from brain  surface of cerebral hemisphere is covered by cerebral cortex o called grey matter o contains billions of nerve cells o perceptions, memories, plans  nerves in cerebral cortex are connected to other parts of the brain by white matter o abundant in axons, instead of cell bodies  cerebral cortex is wrinkled to increase surface area o bulges= gyri o grooves= sulci, fissures - cells  neurons o nerve cells that bring sensory information to brain, store memories, reach decisions, control activity of muscles o specialized for receiving, processing and transmitting information o types of neurons: sensory (detects sensory info), motor (muscle control), interneurons (intergrates info between sensory and motor neurons) o parts of a neuron: soma (cell), dendrite (receives messages), node of Ranvier (jumps from node to node), axon (carries messages AWAY from soma), terminal button (end of axon; releases neurotransmitter), myelin sheath (fatty cells that insulate axons, increase speed of messages)  glial cell o provides support for neurons and supplies them with essential chemicals - action potential  travels down axon to terminal buttons; terminal buttons secrete a chemical, which is called a neurotransmitter; neurotransmitter affects activity of other neurons; message is conveyed chemically; action potential= abrupt, short-lived reversal in the electrical charge of an axon  steps of an action potential 1. resting state (inside of cell is negatively charged, outside is positively charged; sodium ion channels closed, potassium ion channels open) 2. sodium ion channels nearest to cell body open (sodium ions enter, reversing the membance potential at that location, cell becomes more positive) 3. reversal causes nearby ion channels to open (produces another reversal at that point, will only generate if it reaches threshold of activation=-55 millivolts, continues down towards terminal buttons with brief depolarizations along the cell membrane) 4. sodium ion channels close & potassium ion channels open (cell has reached max. positive charge of +40 millivolts, K+ ions leave restoring membrane potential- repolarization occurs) 5. hyperpolarization occurs (cell becomes temporarily more negative than resting state at -80 millivolts; called refractory period) 6. ion transporters pump sodium ions out & potassium ions back in (restores normal balance at resting state)  all or none law: once an action potential is triggered, it is propogated, without getting smaller, to the end of the axon o action potentials are all the same size o quantitative information is represented by an axon’s rate of firing - synapses  neurons communicate with other cells by forming synapses  steps of synapse: 1. axon’s terminal buttons has synaptic vesicles o little bubble of membrane filled with neurotransmitter 2. action potential reaches terminal buttons on presynaptic neuron 3. terminal button releases a small amount of neurotransmitter into synaptic cleft 4. neurotransmitter diffuses across synaptic cleft to postsynaptic neuron 5. neurotransmitter attaches to neurotransmitter receptors on membrane of postsynaptic neuron o key and lock model- specific match 6. once activated, receptor molecules produce inhibitory or excitatory effects on postsynaptic neuron o produce effects by opening ion channels o excitatory synapses= make it more likely the axon of postsynaptic neuron will fire (permit sodium ions to enter neuron) o inhibitory synapses= lower likelihood that axons of postsynaptic neuron will fire (permit motassium ions to leave neuron) 7. inhibition or excitation are short lived- effects are terminated by reuptake or enzymatic breakdown o neurotransmitter is quickly taken up again by the terminal button o neurotransmitter is converted into a chemical by an enzyme (enzymatic breakdown) o the faster neurotransmitter is taken back, the shorter its effects will be Drugs and Behaviour - 2 types of drugs  transmitter agonist: enhances neurotransmitter’s actions  transmitter antagonist: reduces/ block neurotransmitter’s actions - 3 ways drugs alter synaptic transmission 1. stimulate or inhibit the release of neurotransmitters o drugs can cause terminal buttons to release neurotransmitter continuously o drugs can prevent terminal buttons from releasing their neurotransmitter 2. stimulate or block postsynaptic receptors o drugs can turn receptors on, even when the neurotransmitter is not present (act like “master key”) o drugs can bind with receptors but not stimulate them, making them inaccessible (plugs up lock, so key can’t fit) 3. inhibit reuptake o molecules of neurotransmitter continue to stimulate postsynaptic neuron for a long time - 2 most important neurotransmitters 0. glutamate o excitatory effects o alcohol desentizes NMDA receptor (type of glutamate receptor) 1. GABA o inhibitory effects o barbituates, alcohol, benzodiazepins (antianxiety drugs) desensitize GABA receptor - other neurotransmitters  acetylcholine (ACh) o excites muscular contraction, activates cerebral cortex, controls REM sleep, controls hippocampus o effects are terminated by enzyme AChE o botulinum toxin blocks release of ACh o black widow venom stimulates release of ACh o neostigmine blocks AChE (reuptake) o nicotine stimulates ACh receptors o curare blocks ACh receptors  monoamines o dopamine (facilitates movement, attention, reinforcement; L- DOPA increases synthesis of DA; amphetamine, cocaine inhibit reuptake of DA; antipsychotic drugs block DA receptors) o norepinephrine (increases vigilance) o serotonin (regulates mood, controls eating, sleep, arousal; Prozac inhibits reuptake of serotonin; LSD stimulates serotonin receptors)  peptides o most neuromoduators are peptides (substance secreted in brain that acts on appropriate receptors) o consist of two or amino acids attached by peptide bonds o best known are endogenous opiods (reduce pain, reinforce ongoing behaviour; opiates stimulate opioid receptors; naloxone blocks opioid receptors)  endogenous cannabinoid o neuromodulator o nausea reduction, decreased pressure in eyes, affects short- term memory, increased appetite o THC stimulates cannabinoid receptors Control of Behaviour - localization of function  some believed functions were localized to particular regions of the brain  some believe every part of brain does same thing  aphasia= language disorder resulting from brain damage o proof of localization o shows language depends on different parts of left side of brain  Broca’s aphasia o primary difficulty is producing language o little problem understanding language o damage to the left inferior frontal gyrus  Wernicke’s aphasia o cannot understan speech; their own speech doesn’t make sense o can still produce speech o damage closer to back of brain than in Broca’s aphasia - lateralization of fuction  some fuctions are lateralized= located primarily on one side of the brain  left hemisphere- analysis of information, serial events (talkimg, understanding language)  right hemisphere- synthesis, drawing, read maps  corpus callosum= large bundle of axons that connects hemispheres o each region knows what is happening in corresponding region on other side of brain - main structures  brain stem o contains medulla, pons, midbrain o lowermost part of brain o automatic processes- breathing, blood pressure sleep, etc o relays sensory information to brain areas  cerebellum o connected to back of brain stem o controls movement o computer that compares location of body parts with intended movements o damage produces uncoordinated movements o monitors information regarding balance and posture o essential for some kinds of motor learning  hypothalamus o controls autonomic nervous system and many behaviours related to regulation and survival o controls pituitary gland, which controls other endocrine glands o controls autonomic nervous system  thalamus o relays almost all sensory info to cortex o prevents sensations from entering during sleep  basal ganglia o initiation of planned movement o learned and procedural memory  limbic system o emotional beahviour o structures  amygdala: damage causes changes in emotional and aggresive behaviour  hippocampus: important roles in memory and learning  cerebral cortex o controls most complex mental functions o 4 lobes: frontal, parietal, temporal, occipital o various cortexes throughout  perceiving, learning, remembering and planning take place in association areas  sensory association cortex receives information from primary sensory areas  motor association cortex controls the primary motor cortex - lobes  1) occipital lobe: vision o contains primary visual cortex  visual perception o total damage of primary visual cortex  blindness o damage to visual association cortex  prevents people from recognizing objects by sight  visual acuity still good  visual agnosia  2) temporal lobe: audition o contains primary auditory cortex  sensitive to speech and language  object recognition o contains hippocampus and amygdala o damage to primary auditory cortex  hearing losses  3) parietal lobe: somatosensation & spatial perception o contains primary somatosensory cortex  touch information o damage to right parietal lobe  difficulty with spatial tasks  perceptual difficulties o damage to left parietal lobe  can’t make precise hand movements  difficulty identifying parts of body  difficulty performing arithmetic calculations  4) frontal lobe: planning & moving o contains primary motor cortex  commands voluntary movements of parts of body  damage to primary motor cortex (paralysis of the side of body opposite to brain damage) o contains prefrontal cortex  interprets social cues, interpersonal behaviour  damage to prefrontal cortex (contains motor association) Week 8 & 9: Chapter 5: Sensation Sensory Processing - transduction= sense organs convert energy from environmental events into neural activity  brain does not perceive objects directly - 3 ways sensory systems transmit information to brain: 1. anatomical coding/place coding/labeled-line coding  different features are coded by the activity of different neurons in different places - primary cortexes contain “neural maps” 2. temporal coding  different features are coded by the rate of firing of a neuron 3. population coding/ pattern coding  different features are coded by the pattern of stimulation across a group of neurons - spontaneous rate  neurons fire randomly when no stimulus is present  rate of firing indicates stimulus’ intensity - sensory adaptation  occurs when sensory neurons are fatigued o few seconds of steady, continuous stimulation  system is less responsive if stimulus is continuously presented o can ignore unimportant stimuli and be ready for something important - threshold  point at which a stimulus, or change in the value of a stimulus can be just detected  point at which participant detects stimulus 50% of time - difference threshold  another name for jnd - absolute threshold  minimum value of stimulus that can be detected  observers detect it here 50% of the time - just-noticeable difference (jnd)  smallest change in magnitude of stimulus that a person can detect  Weber found it was easier to detect a very small increase in weight with lighter weights, rather than heavier ones  Weber’s law= JND/ initial intensity is a constant - measuring sensations  assumed jnd was basic unit of sensory experience o thought each jnd was an equal step in magnitude of sensation  measured absolute magnitude of sensation in jnds  Fechner’s law=relationship between physical intensity of stimulus and its psychological magnitude in jnd - Steven’s Power Law  accounts for sensation over a greater range of intensities  people assigned numbers of stimuli over different magnitudes o people were consistent- Fechner’s law held over narrow intensities, but did not always hold at high stimulus values - signal detection theory  detection of faint stimuli depends on sensitivity and expectation o response bias- affect decision about whether or not sound was heard  external noise and spontaneous rate (minimum rate of firing of neurons) play a role as well  SDT proposes no such thing as absolute threshold o independent assessment of sensitivity and bias o shown on receiver- operating characteristic plots  present two trials: one with stimulus present, one with stimulus absent- measures detection and bias Vision - different wavelengths of visible lights have different colours - all other radiant energy in electromagnetic spectrum is invisible to eyes - eyes can only detect visible spectrum - eye  cornea o bulge at front of eye, admits light  sclera o tough, white membrane that coats rest of eye  iris o muscles that control amount of light admitted, and thus the size of the pupil  aqueous humour o watery fluid behind cornea that nourishes cornea (aqueous humour builds up-> increases pressure in eye-> causes glaucoma)  lens o organ behind iris that helps focus images on the retina  accommodation= lens changes shape to adjust for distance o normally, length of eye matches bending of light rays by cornea  eyes are too long= nearsighted= need concave lens  eyes are too short= farsighted= need convex lens  retina o tissue of back of eye that contains the photoreceptors and associated neurons  130 million photorecptors= specialized neurons that transduce light into neural activity  optic disc o info from photoreceptors sent to this point at back of eye o axons leave eye here, join optic nerve, travel to brain  optic nerves of each eye exhange some fibres at optic chiasm so some information from left visual field goes to right visual cortex o no photoreceptors here- blind  retina has 3 layers: o light passes through ganglion cells-> bipolar cells-> photoreceptors o photorecptors respond to light and send it backwards: photoreceptors: photoreceptors-> bipolar cells-> ganglion cells-> optic nerve  retina has 2 types of photoreceptors o rods (125 million): function in dim light, cannot detect changes in hue o cones (6 million): daytime vision, colour perception  fovea o small pit in back of retina o contains only cones o one cone connected to one ganglion cell- responsible for finest vision o away from fovea, cones decrease and rods increase  many rods connected to one ganglion cell- much convergence  evidence for 2 types of photoreceptors o dark adaptation  dark adaptation curve is not a simple curve  two mechanisms must be involved to create the “bump” o colour processing in dim light  see colour in bright light; see shades grey in dim light  loss of colour in dim light? o Purkinje shift  yellows and reds most brilliant during midday  greens and blues are more brilliant in the evening - transduction of light  steps of transduction: 1. photoreceptors contain 4 kinds of photopigments (1 for rods, 3 for cones) 2. photon (particle of light) strikes photopigment 3. photopigment breaks into its two molecules: molecule from vitamin A & protein 4. splitting causes chemical reactions that stimulate photoreceptors to send message  intact photopigments have a colour o rods are pink  once photopigments are split, they become bleached  energy from photoreceptor’s metabolism causes two molecules to recombine  entering dark room after being in light o too few rhodopsin molecules intact to respond immediately to dim light o regeneration occurs and eye has undergone dark adaptation - eye movements  vergence movement o keep both eyes fixed on same target o image of object falls on same portions of both retinas  saccadic movement o rapid movement used in scanning a visual scene  pursuit movement o “tracking movements” o maintain an image of a moving image upon the fovea - colour vision  DImensions of colour o hue o brightness o saturation o colour mixing (yields brighter colour ex. red light + green light= yellow light) o pigment mixing (yields darker ex. blue + yellow paint= green paint)  2 theories of colour coding o 1) trichromatic theory  Young and Helmholtz  eye contain three types of colour receptors/ cones, each sensitive to a different hue  combine information from each cone to see different colours  receptors sensitive to blue, green and red o 2) opponent process theory  Hering  four pure hues belong to pairs of opposing colours: red/green, blue/yellow (eg can see reddish-blue but not greenish-red)  two types of ganglion cells encode colour vision: red/green, blue/yellow o both fire at steady rate when not stimulated o red excites red/green cells-> causes them to fire at higher rates o green inhibits red/green cells-> causes them to fire at slower rates o similarly, yellow excites and blue inhibits yellow/blue cells o brain learns about colour by increased or decreased firing  negative afterimages o explained by opponent process theory o caused by adaptation to the rate of firing of retinal ganglion cells o if excited or inhibited for a long time, they show a rebound effect  fire faster or slower than normal when looking at a new stimulus  eg. look at red image-> high rate of firing, then look at colourless image-> reduced rate of firing interpreted as green Audition - stimulus= sound  waves of vibrating air molecules that involves the compression and expansion of molecules of air - characteristics  loudness= amplitude  pitch= frequency of vibration  timbre= complexity of vibration o can distinguish different instruments when playing the same note - ear  pinna o outer ear o funnels sound through ear canal  ear canal o carries the sound  eardrum/ tympanic membrane o vibrates in response to sound waves o passes vibrations onto receptor cells in inner ear  ossicles o middle ear bones attached to eardrum o transmit vibrations to receptive organ  stapes o last middle ear bone o vibrates and presses on oval window  oval window o transmits sound vibrations into the fluid in the cochlea  cochlea (inner ear) o receptive organ o base is basilar membrane, with auditory hair cells on top o basilar membrane vibrates back and forth when stapes presses on oval window  high frequency sounds cause end near oval window to vibrate; low-frequency sounds cause tip to vibrate o auditory hair cells have cilia embedded in tectorial membrane (above basilar membrane)  cilia stretched when basilar membrane flexes-> pull on cilia translates into neural activity o electrical charge across membrane altered-> neurotransmitter released at synapse between hair cell and auditory nerve - detecting sounds  pitch o tonotopic organization- place code o signaled by which neurons fire o temporal code used for lower frequencies  loudness o signaled by number of cells that are active (ex. louder excited more hair cells)  timbre o depends on relative amplitudes of sound waves o many different portions of basilar membrane flex simultaneously during a complex sound o pattern recognition- particular patterns of constantly changing activity received from hair cells belong to different sound sources  3 ways ear locates sound o elevation= sound coming from above, below, in front, behind  affected by shape of pinna o timing cue  if sound is on midline, sound arrives at both ears at the same time  if sound is to the side, it will arrive at furthest ear later- brain detects difference to locate sound o intensity cue  head shadows sounds, so they are less intense at the far ear Gustation - receptors  papillae o bumps on tongue that contains a number of taste buds  taste bud o contains a number of receptor cells o hair-like projections called microvilli  molecules of saliva stimulate receptor cells, which form synapses with neurons that send axons to the brain - qualities of taste  sweet, sour, salty, bitter, umami (MSG) Olfaction - olfactory mucosa  located on roof of nasal sinuses  contains receptor cells with cilia implanted in olfactory mucosa  receptor cell is excited when molecule of odorous substance fits receptor molecule - olfactory bulbs  receives message from olfactory receptors  sends messages to limbic system and primary olfactory cortex via the olfactory nerve - odours are inidentified based on a population code  different odorants bind to different receptor cells  unique firing pattern occurs across fibres of olfactory nerve Somatosenses - body senses from internal and external environment (pain, coolness, tilt of head) - skin senses  touch (pressure/ vibration) o skin surface projected to primary somatosensory area  has a topographic map of the body= homunculus o areas with highest sensitivity to touch have largest representation in brain  small jnds are on face and hands  temperature o thermoceptors in skin= free nerve endings  pain o sensory receptors are free nerve endings o 3 types of receptors: extreme pressure, extreme hot and cold, tissue damage o phantom limb pain- pain in patients after a limb has been amputated - internal senses  sensory endings located in internal organs o muscles contain special sensory endings that provide information about amount of force muscle is exerting o pressure receptors in joints are stimulated by contact between joint surfaces  contact occurs when angle of bones changes - vestibular senses  keep balance o vestibular apparatus of inner ear helps us remain upright o detectors in vestibule inform us of movement forwards/ backwards/ upwards/ downwards o semicircular canals in inner ear detect changes in rotation of head Week 9: Chapter 6: Perception - structuralist account- sensations are building blocks of perception - Gestalt account- predispositions to perceive things in certain ways- we perceive whole objects - ecological account- evolved to detect what is important in the world - constructivist account- actively interpret incoming sense data Brain Mechanisms - surface of retina mapped onto primary visual cortex - neurons within a module receive information from same small region of retina - 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