Introduction to Physiological Psychology Review ksweeney@cogsci.ucsd.edu 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 Perceptual Learning Objects Situations Forms of Learning Motor Learning Stimulus-Response Learning Relational Learning Form new circuits in the motor system Form connection between perception and action 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 twothirds 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 n Language Even for deaf people! n Words, letters Right Hemisphere n Emotional Prosody n Music n Spatial ability 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
n Wernicke s area is also implicated in Pure Word Deafness n Uncompromised recognition of nonspeech sounds and intonation. n Caused by disruption of auditory input to Wernicke s area, or damage to Wernicke s area itself Wernicke s Area Transcortical sensory aphasia n Wernicke s aphasics can t understand the meaning of words or translate their thoughts into meaningful words. n This seems to be due to trauma to the posterior language area. n Damage to just this area often results in transcortical sensory aphasia. n These patients can recognize words: they can repeat back what you say but can t make meaning. 23
Language Areas Conduction Aphasia n The fact that transcortical aphasia patients can perform repetition suggests that there is a direct connection between Wernicke s area and Broca s area n This is known as the arcuate fasciculus 24
Conduction Aphasia n Conduction aphasia patients speak fluently have pretty good comprehension Often perform well on repetition tasks, as long as the sounds have meaning Often fail at longer repetition tasks, repeating the gist of a sentence but with different words The arcuate fasciculus n A bundle of axons that seems to bring information from Wernicke s area to Broca s area about the sounds of words (but not their meanings!) n Conduction aphasia patients speak fluently, have pretty good comprehension, but fail at repetition tasks suggesting that the AF is important in STM of words and recently heard speech sounds 25
Conduction aphasia Anomic aphasia n Speech of anomic aphasics is fluent and grammatical, and their comprehension is fine but they appear to have difficulty finding the right words. n Fluent anomia is caused by posterior lesions to the temporal or parietal lobes. n Patients adopt circumlocutions: alternative ways of saying what they mean 26
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