NOTE: This first slide about the structure of the neuron will not appear in class until approximately week 3. Until then, there are no PowerPoint slides, only web page links. After that, this file will be expanded to include more slides as we progress through them over the course of the semester.
The Neuron: number: 10 billion to a trillion 10,000 connections each parts: dendrites cell body (or "soma") axon terminal endings (or terminal buttons) questions: 1) how does a neuron "fire"? (what is the nerve impulse?) 2) how does it cause the next neuron to fire? (how does it communicate?)
nerve impulse = ACTION POTENTIAL: 1) start with electrical RESTING POTENTIAL: inside of cell is 70 mV more negative than outside due to Cl- ions inside and Na + ions outside (so RESTING POTENTIAL is -70 mV). 2) stimulation of neuron lets in Na+ ions, which makes the inside more positive: -70,-69,-68,-67... 3) when enough Na+ ions get in for the potential to be reduced to -55 mV, suddenly the doors (ion gates) to the cell membrane are flung open allowing Na+ to rush in. 4) so much Na+ enters that the potential doesn't just go to 0 -- it shoots all the way up to +40 mV, so the inside is now positive relative to the outside (the ACTION POTENTIAL) 5) ion pumps work to reduce potential back to -70 mV by pushing positive ions out (actually K+ because Na+ goes out slower; then ANOTHER pump takes Na+ back out and puts K+ back in)
ACTION POTENTIAL (continued)... - note that -55mV is a threshold: below that voltage there is no action potential - firing is "all-or-none" - more intense stimulation doesn't cause a more intense action potential -- just more frequent ones (up to 1000/sec!), and in more neurons - action potential travels down length of axon by depolarizing neighboring areas - travels NOT at speed of electrical current in wire, but rather at about 50 to 100 m/sec
communication across the synapse: NEUROTRANSMITTERS 1) synapse is gap between two neurons (the presynaptic and the postsynaptic neurons); terminal endings of presynaptic neuron relay impulse to dendrites of postsynaptic neuron 2) terminal buttons contain little sacs ("vesicles") of chemicals ("neurotransmitters"); at action potential, vesicles burst and release neurotransmitters into synapse 3) receptor molecules on membrane of dendrite are like little locks to be opened: neurotransmitters are the keys, and this is what opens ion gates to allow Na+ inside in the first place 4) neurotransmitters may open a gate to let Na+ inside: excitatory (more likely to fire) because potential is getting smaller, toward -55 - or they may open a gate that pushes positive K+ ions out: inhibitory (less likely to fire) because potential is getting larger (e.g., -70, -71, -72...)
central nervous system (CNS) - "center"; includes brain and spinal cord peripheral nervous system - "away from center"; includes everything but brain and spinal cord A. somatic division - "body" - nerve fibers connecting to muscles, senses B. autonomic division (ANS) - "self rule" - regulates vital functions: heart rate, breathing, digestion, etc. 1. sympathetic branch ("with feeling") - excited states; energy-consuming; arousal: mobilizes for emergency (speeds heart and lungs, inhibits digestion and sex, etc.) 2. parasympathetic branch ("goes with sympathetic") - vegetative states; energy-conserving or storing; calm: maintains normal functioning (slows heart and lungs, etc.)
BRAIN: bottom to top (= inside to outside = old to new) hindbrain: medulla - breathing, heartbeat, blood circulation pons - arousal and attention cerebellum - integration of muscles to perform fine movements, but no coordination / direction of these movements; balance - cat transected above hindbrain: can move but not act midbrain: forms movements into acts; controls whole body responses to visual and auditory stimuli - cat transected above midbrain can act, but without regard to environment: without purpose forebrain: thalamus - sensory and motor relay center (to various cerebral lobes) hypothalamus - controls responses to basic needs (food, temperature, sex) basal ganglia - regulates muscle contractions for smooth movements limbic system - memory (hippocampus) and emotion (amygdala) cerebral cortex (or "neocortex") - four lobes (frontal, parietal, occipital, temporal); seat of "higher" intellectual functions - cat transected above limbic system: acts normal, with purpose - but clumsy
CEREBRAL HEMISPHERES (or CEREBRUM): corpus callosum: connects hemispheres - each hemisphere controls OPPOSITE SIDE of body cerebral cortex (= skin or bark): - 1 to 3 mm thick; 2 or 3 ft square if flattened out - higher motor, sensory, and intellectual functions FOUR LOBES of cortex: frontal lobe: planning; social behavior; motor control - front of brain parietal lobe: somatosensory (sense of touch) - on top and toward back of brain occipital lobe: vision - back of brain temporal lobe: hearing; memory - side of brain
TWO GENERAL RULES of cortical function: 1. Left Hemisphere: language Right Hemisphere: spatial abilities 2. Front: expression / actions / plans Back: reception / perceptions / interpretations
DAMAGE TO NON-PRIMARY ("ASSOCIATION") CORTEX: pre-frontal lesions: loss of planning, moral reasoning, sensitivity to social context - or... loss of initiation of action, deliberation apraxia ("no doing"): failure in sequencing components of actions; inability to organize familiar movements - FRONTAL - lesions just forward of motor cortex - NOT paralysis, as from motor cortex lesion agnosia ("no knowing"): - deficit in interpreting, categorizing, labeling, knowing - OCC (visual) or TEMP (auditory) lesions - sensory systems themselves (e.g., eyes) are okay neglect: RIGHT hemisphere (PAR) damage causes inattention to whole left side aphasia: LEFT hemisphere (FRONT or TEMP) damage causes deficits in language function...
APHASIA: disorder of language - left hemisphere brain lesions - essentially apraxia (if lesion is in front) or agnosia (if lesion is in back) OF LANGUAGE expressive aphasia: cannot produce speech - lesion to BROCA'S AREA (frontal association area) receptive aphasia: cannot understand speech - and consequently cannot produce speech! - lesion to WERNICKE'S AREA (back association area)
SPLIT BRAIN STUDIES - sever corpus callosum to reduce severity of seizures - leaves patient mostly normal, but with left and right brain independent in subtle ways note visual pathways: left side of each eye sends info to left hem. right side of each eye sends info to right hem. - result: left visual field goes to right hem. right visual field goes to left hem. experiment on split brain patient: - patient looks straight ahead; picture flashed quicker than eyes can move; ask "what did you see?" - picture of cup on right: LH says "cup" picture of spoon to left: LH says"nothing" - BUT when told to reach for that object with the left hand, RH grabs spoon - ask "what is it?" and LH guesses "pencil" (and RH may frown at that)
THE FOLLOWING CORRESPONDS TO THE MATERIAL AT THE BEGINNING OF THE CHAPTER ON LEARNING, WHICH IS IN THE ASSIGNED READING FOR EXAM 1 CLASSICAL CONDITIONING - US (unconditioned stimulus - e.g., food in mouth): input to a reflex - UR (unconditioned response - e.g., salivation to food): output of reflex - CS (conditioned stimulus - e.g., bell): initially results in investigatory response, then habituation; after conditioning, results in CR - CR (conditioned response): response to CS; measure amplitude, probability, latency
END OF MATERIAL FOR EXAM 1
extinction and spontaneous recovery: - extinction: CR declines and disappears over trials without US; due to buildup of inhibition - spontaneous recovery: after rest interval, extinguished CR reappears at almost previous strength, and extinguishes faster next time; due to dissipation of inhibition observations on conditioning: - involuntary responses involved - contiguity: closeness in time is basis of acquisition of conditioned reflex (...?) - optimal time interval between CS and US differs depending on particular reponse being conditioned (e.g., 5-30 sec for dog's salivation response, .5 sec for human eyeblink response); no. of trials required for conditioning varies too! - more intense CS produces greater CR (e.g., louder tone, brighter light -> more salivation)
higher order conditioning: 1) establish CS (e.g., bell->salivation) 2) new CS is paired with old CS without US (e.g., tone->bell->salivation) 3) eventually, new CS is established without US (e.g., tone->salivation) - call this "second-order conditioning" - US acts as reinforcer for conditioned reflex - in higher order conditioning a CS acts like a US ("secondary reinforcer") generalization: similar stimuli produce similar responses (pet both dogs and cats) - new stimulus similar to CS also produces CR (e.g., different pitch tone still produces salivation) discrimination: different stimuli produce different responses (say "dog" and "cat" appropriately) - train "CS+" (high tone with US) and "CS-" (low tone w/o US): result is CR to CS+ but not to CS-
CR not same as UR: CR may be preparatory response for US - CS tone->US shock->UR fast heartbeat, breathing but then: CS tone->CR slower heartbeat, breathing - CS injection->US morphine->UR less pain but then: CS injection->CR more pain sensitivity What gets learned? - Pavlov's view: CS-CR conditioned reflex - modern view: CS-US association, such that CS provides info about US - note: backward conditioning (US before CS!) fails
INSTRUMENTAL or OPERANT CONDITIONING cats in puzzle box (Thorndike, 1898) - trial and error; incremental learning - Law of Effect - response is automatically strengthened when followed by reinforcement ("satisfying state of affairs"); automatically weakened when followed by punishment ("annoying state of affairs") Operant conditioning vs. classical conditioning: - operant cond. - reinforcement depends on response; class. cond. - reinforcement (US) comes regardless - operant response is emitted and voluntary; classical cond. response is elicited and involuntary - What is learned? in operant cond. - a BEHAVIOR in classical cond. - a SIGNAL (CS- ->US) - Through what mechanism? operant: Law of Effect: CONSEQUENCES of behavior (but delay of reinforcement weakens response!) classical: CONTIGUITY... so far! - "conditioning", because changing the conditions changes response frequency; not under conscious control even though voluntary! B.F. SKINNER - "Skinner box": many responses, little time and effort, easily recorded - RESPONSE RATE is the Dependent Variable
REINFORCEMENT AND PUNISHMENT - REINFORCEMENT (both pos. and neg.) always increases rate of responding - positive reinforcement delivers appetitive stimulus (food, approval); - negative reinforcement removes aversive stimulus (shock, alarm clock noise) - PUNISHMENT decreases rate of responding - w/ NO reinforcement: extinction and spontaneous recovery happen just as in classical conditioning DISCRIMINATIVE STIMULUS: indicates under what circumstances response will be reinforced - ex: rat presses bar, but only gets food when light in box is on; eventually doesn't press unless light is on - stimulus does NOT CAUSE response, or SIGNAL reinforcement; it SETS OCCASION for response parallel to classical conditioning: instead of CR there's operant response; instead of US, reinforcement; instead of CS, discriminative stimulus - but order changes: - CLASSICAL: stim (CS) reinf (US) resp (CR) - OPERANT: stim resp! reinf! conditioned (secondary) reinforcer - stimulus paired with reinforcer acquires reinforcing properties - how does something get to be a conditioned reinf? through classical conditioning! - ex.: in higher order classical conditioning - once bell is connected with food, it's used like a US
partial reinforcement effect: - reinforcing ONLY SOME TRIALS produces even STRONGER response than reinforcing ALL TRIALS - what does "SOME" mean?... SCHEDULES OF REINFORCEMENT: - describe as interval, ratio, fixed, variable (continuous reinforcement = all responses reinforced) interval schedule - reinforcement for next response after some time interval - "fixed interval" (FI) - time is fixed; rat gets food pellet for next bar press, say, 30 seconds after last pellet (like checking mail, delivered daily) - "variable interval" (VI) - time is average; rat gets food pellet for next bar press 20, 40, 25, 35 seconds after last pellet, etc. - 30 seconds on average (like checking e-mail, delivered whenever) ratio schedule - reinforcement after some number of responses (ratio of responses to reinforcements) - "fixed ratio" (FR) - ratio is fixed; rat gets food pellet for every 10th bar press (like factory piecework) - "variable ratio" (VR) - ratio is average; rat gets food pellet after 8, 12, 5, 15 responses - 10th response on average (like gambling) shaping - differential reinforcement of successive approximations to desired response - can produce a response the animal would never have made spontaneously on its own - "chaining" together responses into long sequence allows training of very complex behaviors
CONTINGENCY, NOT CONTIGUITY, is what matters in classical conditioning - Robert Rescorla (1968): exp't on what it takes to make a signal work (-- more than just contiguity!) 3 groups of rats all hear tone lasting for 2 minutes; when tone is ON, probability of shock = 40% - all 3 groups have same degree of contiguity of tone and shock: shock is on for 48 sec out of 120 sec - but vary p(shock) for 3 groups when tone is OFF: grp 1: without tone playing, p(shock) = 40% grp 2: without tone playing, p(shock) = 20% grp 3: without tone playing, p(shock) = 10% - results: grp 1 shows NO fear conditioning to tone grp 2 shows some fear, but less than grp 3 grp 3 shows strong conditioned fear of tone - what does tone say to grp 3? "your 10% now goes up to 40%, so BE SCARED!" what does tone say to grp 1? "your 40% stays the same; sure, life sucks, but it's BUSINESS AS USUAL!" CONTINGENCY: how the US depends on the CS - "probability of US in presence of CS" relative to "probability of US in absence of CS"
BELONGINGNESS - biological preparedness to make certain associations - Pavlov assumed: ALL ASSOCIATIONS ARE ARBITRARY CONTIGUITY CAUSES CONDITIONING - Garcia and Koelling (1966) exp't used 4 groups: US = shock OR illness (produced by X-ray or LiCl) CS = light and sound OR saccharin taste in test: US: shock illness CS light / sound AVOID DON'T AVOID taste DON'T AVOID AVOID - light/sound-shock group avoided bright noisy water light/sound-illness group did not avoid bright noisy water taste-shock group did not avoid saccharin water taste-illness group avoided saccharin water - CS and US had to be both inside (taste-illness) or both outside (light and sound) of animal - "Garcia Effect": special facility for learning taste aversion (taste-illness association) - difficult for classical conditioning because 1) association established in one trial; 2) up to 24 hrs between CS and US; 3) very resistant to extinction Pavlov's assumptions revisited: ARBITRARINESS: NO - associations are selective CONTIGUITY: NO - very long CS-US intervals
[NOTE: slides on "Learned Helplessness" and "Latent Learning" are provided for their potential usefulness as summary descriptions of those phenomena even though they may not be used in lecture.] cognitive learning - Edward Tolman (1930's-1950's): - learning is NOT just automatic response-strengthening (in Thorndike's sense) - ex.: "contingency" in classical conditioning LEARNED HELPLESSNESS (Martin Seligman) - learning that actions have no effect on world - Phase I (classical): Dog A and Dog B shocked at same time Dog A can stop shock for both - ESCAPABLE Dog B cannot stop shock at all - INESCAPABLE - Phase II (operant): Each dog in own two-part box divided by barrier Hear tone followed by shock after 10 sec Dog A learns to jump barrier when tone plays Dog B does not - howls, whines, whimpers, accepts - In Phase I, animal learns: (1) relation between CS and US, and (2) what it does has no effect on US (shock) - experienced as depression in humans LATENT LEARNING: rats ran around maze at leisure for 10 days, then for food from 11th day on... - Thorndike / Skinner: learning begins when reinforcement begins - rats should run slow for 10 days, then gradually get better starting from that 11th day...but instead: - Tolman found running was slow for 10 days, then was suddenly fast from 11th day on - they had learned it gradually over the 10 days, but didn't show it (it was latent) until motivated (i.e., until they got food at the end) Conclusion: learning is NOT caused by reinforcement learning IS a building up of "cognitions" BEHAVIORIST view would say response is learned automatically, due to reinforcement - we know response is learned when rat performs it COGNITIVE view says "cognitive map" of maze is learned (even without reinforcement) - used later when animal has purpose or motivation
HUMAN MEMORY stage theory: Long Term and Short Term Memory - (note: Short Term Memory = "Working Memory") duration - Long Term Memory: relatively permanent - Short Term Memory: seconds to minutes storage capacity - Long Term Memory: infinite? - Short Term Memory: 7+/-2 "chunks" (organized packets of information) flow of information in memory - stimulus -> STM -> rehearsal* -> LTM *two kinds of rehearsal: maintenance - holds info in STM elaborative - moves info to LTM
serial position effect in free recall - task: read 20 words one at a time, recall in any order - primacy effect - early part of list recalled better than middle: recalled from LTM - recency effect - last part of list recalled better than middle: recalled from STM reduce recency: delay between 20th word and recall reduce primacy: present words faster
END OF MATERIAL FOR EXAM 2
FURTHER DIFFERENCES BETWEEN STM & LTM psychological code - STM: phonological - based on speech sounds - LTM: semantic - based on meaning neural code... - STM: dynamic - pattern of activity among a group of cells - LTM: structural - pattern of connections within a group of cells - "trace consolidation" is what goes on during elaborative rehearsal - a memory trace changes from a dynamic to a structural pattern - amnesia - interruption of consolidation process - retrograde amnesia for events BEFORE trauma - anterograde amnesia for events AFTER trauma
forgetting - STM: DISplacement and/or decay - LTM: MISplacement and/or retrieval failure - proactive interference: old info affects new - retroactive interference: new info affects old WORKING MEMORY - STM not just storage box; more like cognitive "workbench" - limit on storage capacity is viewed instead as limit on processing capacity - used in all processing of information: mental calculation, reading, etc. (16 x 231=?)
DEPTH OF PROCESSING - what kind of encoding will be most successful?... deeper (more meaningful) processing leads to better memory - connected to notion of elaborative rehearsal - Craik and Tulving (1975) experiment
KINDS OF MEMORY: long-term vs. short-term ("working memory") episodic (episodes, events with time and place): "I saw an elephant at a zoo in 2008." vs. generic / semantic (facts, concepts and meanings): "An elephant has big floppy ears and a trunk." explicit (reference to prior learning experience) recall - "what were the words on the list you read?" recognition - "circle the words you saw earlier" vs. implicit (no conscious awareness of remembering) priming - read list of words then do tasks... stem completion - "MOT_____" word fragment completion - "__U__O__O__I__E" declarative = knowing that (mainly explicit) statements, using episodic and generic information vs. procedural = knowing how (mainly implicit) skills: riding a bike, playing an instrument,etc. [story of Henry ("H.M.") - anterograde amnesia for explicit memory, resulting from surgical removal of hippocampus and other limbic regions]
RETRIEVAL ENCODING SPECIFICITY PRINCIPLE (or COMPATIBILITY PRINCIPLE): - retrieval cue - current stimulus that aids retrieval - any memory for an item has the item's context wrapped up in it too - context (cues) at retrieval should be as much as possible like context at encoding ex.: learn list - "figure, data, diagram, table, chart, graph..." - then "FURNITURE" would not be a good retrieval cue for "table" ex.: learn list - "Ford, Honda, Toyota, Saturn, Lexus..." - then "RINGS" would not be a good retrieval cue for "Saturn" IS RETRIEVING A MEMORY LIKE PLAYING BACK A TAPE? Loftus and Palmer (1974) experiment: 1) view slides of car accident (no broken glass pictured) 2) ask: "How fast were the cars going when they hit each other?" or: "How fast were the cars going when they smashed into each other?" 3) 1 week later: "Did you see any broken glass in the pictures?" YES response more likely for "smash" group than for "hit" group CONCLUSION: at least in part, memory involves reconstruction of remembered information - memory may be distorted by other information
GENERIC MEMORY - retrieval = search through network of concepts - organized according to semantic relatedness (closeness of meaning) - activation of one concept spreads to other related concepts - "What does 'Rosebud' mean?" "Do chickens have lips?" "How many arms did Aristotle have?" "How many ears did Vincent van Gogh have?"
SENSATION: basic, primitive mental state corresponding to energies in env't; EXPERIENCE of world PERCEPTION: mental state corresponding to properties of objects and events in env't; KNOWLEDGE of world
CONTINUED ON POWER POINT SLIDES AT http://media.pluto.psy.uconn.edu/sensationperception%20slides%20post.pdf
including several slides that were not used in lecture but may be helpful anyway.