Introduction to Physiological Psychology Review [email protected] www.cogsci.ucsd.edu/~ksweeney/psy260.html n Learning and Memory n Human Communication n Emotion 1 What is memory? n Working Memory: – Limited capacity (7 +/- 2) – Information can be held for several minutes with rehearsal § (e.g. memory system you use when you have to remember a phone number but have no place to write it down) n Long-term Memory: – Very large capacity – Essentially infinite duration § e.g. memory system you need when you are reminiscing with friends, or taking a final exam Objects Perceptual Learning Situations Form new circuits Motor Learning in the motor system Forms of Learning Stimulus-Response Form connection Learning between perception and action Relational Learning Connections between stimuli 2 Learning n All forms of learning involve changes in the ways that neurons communicate. Stimulus-Response learning n Classical Conditioning – An unimportant stimulus begins to elicit a similar response as an important one – It involves an association between two stimuli, one of which is reflexive n Operant Conditioning (or Instrumental Conditioning) – A particular stimulus begins to elicit a particular response – It involves an association between a stimulus and a response 3 Classical Conditioning n Famous example: Pavlov’s dogs – First, present dogs with food and measure amount of saliva – Then, start ringing a bell just before food is presented (at first, saliva only occurs at presentation of food) – In time, salivation occurs in response to the bell – Conditioning has occurred Classical Conditioning n Unconditional Stimulus- dog food n Unconditional Response- salivation n Conditional Stimulus- bell n Conditional Response- salivation 4 Instrumental (or Operant) Conditioning n Reinforcing stimulus (favorable consequences) § Appetitive stimulus that follows a particular behavior and thus makes behavior occur with greater frequency n Punishing stimulus (unfavorable consequences) § Aversive stimulus that follows a particular behavior and thus makes behavior occur more rarely An association between a stimulus and a response But what has happened in the brain? n Hebb postulated: – the cellular basis of learning involves strengthening of a synapse that is repeatedly active when the postsynaptic neuron fires – “neurons that fire together, wire together” For LTP to occur, the postsynaptic cell must already be depolarized 5 NMDA and AMPA n Glutamate binds to NMDA receptors, which controls a calcium (Ca2+) channel. n So, Ca2+ rushes in, right? NO! 6 NMDA and AMPA n At rest, that same calcium channel is ‘guarded’ by a magnesium ion (Mg2+), so calcium can’t get in through NMDA receptors. n That Mg2+ ion won’t budge unless cell is depolarized. n But cell can’t depolarize unless Ca2+ can get in, right? NO! NMDA and AMPA n If a weak synapse is active by itself, nothing happens… n BUT- if the cell has just fired due to a strong synapse somewhere else on the cell, a dendritic spike will depolarize the membrane… 7 NMDA and AMPA n Depolarization kicks the Mg2+ ion out, and NOW Ca2+ ions can enter the cell. n … and an association between those two synapses is formed. We still don’t have LTP! n Ca2+ ions entering the cell bind with the enzyme CaM- KII n CaM-KII causes more AMPA receptors to to move to post-synaptic membrane. n More AMPA receptors means it’s easier to depolarize the cell in the future. 8 We still don’t have LTP! n Ca2+ ions entering the cell bind with the enzyme CaM- KII n CaM-KII causes more AMPA receptors to to move to post-synaptic membrane. n More AMPA receptors means it’s easier to depolarize the cell in the future. n For Ca2+ to enter the cell, NMDA receptors have to be activated by glutamate AND subjected to depolarization simultaneously. n The fact that both these things must occur together means that NMDA receptors are “coincidence detectors”. n Thus, they are crucial for LTP. 9 Perceptual Learning n The ventral stream – involved with object recognition, continues ventrally into the inferior temporal cortex. n The dorsal stream – involved with perception of the location of objects, continues dorsally into the posterior parietal cortex. n The ventral stream is involved with the what of visual perception; the dorsal stream is involved with the where. Instrumental Conditioning n Circuits responsible for instrumental conditioning begin in sensory association cortices and end in motor association cortex. 10 Instrumental Conditioning n Two major pathways from sensory to motor association areas: – Direct transcortical connections- involved in STM, acquisition of episodic memories and of complex behaviors that involve deliberation or instruction (slow and laborious) – Connections via the basal ganglia and thalamus- which are involved as behaviors become automatic and routine (fast and easy) H.M. 11 What can possibly go wrong? n Anterograde Amnesia: – Amnesia for events occurring after the precipitating event. n Retrograde Amnesia: – Amnesia for events occurring before the precipitating event. The Medial Temporal Lobe: Crucial in the Declarative Memory System n Damage to these areas usually results in anterograde amnesia: patients are unable to form new declarative memories. n Can also result in retrograde amnesia: typically ‘graded’. n Non-declarative memory is not affected. 12 H.M. Effects of Bilateral Medial Temporal Lobectomy n Minor seizure beginning at age 10, major seizures beginning age 16 n Severe, persistent seizure condition- not controlled with anticonvulsants n By mid-20’s, condition was so severe he was unable to work n Surgery at age 27: Bilateral medial temporal lobe resection. n In HM, the amygdala, entorhinal and perirhinal cortices, and about two- thirds of the hippocampus were removed 13 What’s wrong with H.M., and what does it tell us about functions of Hippocampus and MTL? n What CAN he do? – Intellect is normal – Can remember the past (pre-surgery) § He has relatively little retrograde amnesia § His long-term memory is intact – Can carry on excellent, short conversation § His working memory is intact – Can learn new skills at a normal rate- and retains those skills over long periods of time § His procedural memory is intact 14 What’s wrong with H.M., and what does it tell us about functions of Hippocampus and MTL? n What CAN’T he do? – Doesn’t retain new semantic or episodic information – Can’t form new declarative memories. What does H.M. tell us about role of Hippocampus and MTL? n Hippocampus is essential for the formation, but not the storage or retrieval, of long-term declarative memory n Memory depends on Hippocampus for a short duration n Hippocampus does not mediate short-term memory 15 What does H.M. tell us about role of Hippocampus and MTL? n STM and LTM are distinctly separate – H.M. is unable to move memories from STM to LTM, a problem with memory consolidation n Memory may exist but not be recalled – as when H.M. exhibits a skill he does not know he has learned Explicit vs. Implicit Memories n Explicit memories – conscious memories n Implicit memories – unconscious memories, as when H.M. shows the benefits of prior experience 16 Broca’s Area and Patient “Tan” Lateralization of Function n For many functions the hemispheres do not differ and where there are differences, these tend to be minimal n Lateralization of function is statistical, not absolute! – e.g. Right hemisphere has some language abilities 17 Lateralization of Function Left Hemisphere Right Hemisphere n “Language” n Emotional Prosody – Even for deaf people! n Music n Spatial ability n Words, letters n Faces, patterns n The details n The big picture Language n Language is not a unitary ability – Production vs. Comprehension n Production – Requires having something to say, being able to associate that “thing” with words, and making the mouth move appropriately n Comprehension – Begins in the auditory system (detection and analysis of sounds) but there is a difference between recognizing a word and comprehending it 18 What can possibly go wrong? n Aphasia – A difficulty with speech (either production or comprehension) caused by brain damage rather than, e.g. motor deficits or deafness What can possibly go wrong? n Broca’s aphasia – difficulty in language production § Comprehension is normal § Know what they want to say, but can’t say it § “expressive aphasia”, slow laborious speech, full of disfluencies. § Although words are often mispronounced, words that are produced are usually meaningful 19 What can possibly go wrong? n Broca’s aphasia – Typically function words are most compromised, with content words being relatively spared. – Aphasias are a spectrum What can possibly go wrong? n Broca’s aphasia: not ONLY a production problem! – Although comprehension is good, it is not normal – Agrammatism is present in production, and grammatical clues such as word order, tense markers or function words aren’t successfully used in comprehension either. 20 What can possibly go wrong? n Broca’s aphasia: not ONLY a production problem! – Anomia: a difficulty in finding words (in naming things). What can possibly go wrong? n Broca’s aphasia: not ONLY a production problem! – Articulation difficulties: mouth motor movements are disfluent, so words are often mispronounced 21 What else can possibly go wrong? n Wernicke’s aphasia – Wernicke’s area- difficulty in comprehension; but production is generally meaningless § Unlike Broca’s Wernicke’s aphasics generally speak quite fluently, with normal prosody, natural-sounding rhythm and apparently normal grammatical constructions. § “jargon aphasia”, natural sounding rhythm and syntax, but output is meaningless (“word salad”) § neologisms Wernicke’s Aphasia n Difficulty recognizing words n Impaired comprehension (failure to grasp the meaning of words) n Difficulty converting thoughts into meaningful words 22 Wernicke’s Area n Wernicke’s area is also implicated in Pure Word Deafness n Uncompromised recognition of non- speech sounds and intonation.