Perceptual Learning. Motor Learning. Stimulus-Response Learning. Relational Learning

Transcription

1 Introduction to Physiological Psychology Review Learning and Memory Human Communication Emotion 1

2 Working Memory: What is 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) 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 Forms of Learning Perceptual Learning Motor Learning Stimulus-Response Learning Relational Learning Objects Situations Form new circuits in the motor system Form connection between perception and action Connections between stimuli 2

3 Learning All forms of learning involve changes in the ways that neurons communicate. Stimulus-Response learning 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 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

4 Classical Conditioning 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 Unconditional Stimulus- dog food Unconditional Response- salivation Conditional Stimulus- bell Conditional Response- salivation 4

5 Instrumental (or Operant) Conditioning Reinforcing stimulus (favorable consequences) Appetitive stimulus that follows a particular behavior and thus makes behavior occur with greater frequency 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? 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

6 NMDA and AMPA Glutamate binds to NMDA receptors, which controls a calcium (Ca2+) channel. So, Ca2+ rushes in, right? NO! 6

7 NMDA and AMPA At rest, that same calcium channel is guarded by a magnesium ion (Mg2+), so calcium can t get in through NMDA receptors. That Mg2+ ion won t budge unless cell is depolarized. But cell can t depolarize unless Ca2+ can get in, right? NO! NMDA and AMPA If a weak synapse is active by itself, nothing happens 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

8 NMDA and AMPA Depolarization kicks the Mg2+ ion out, and NOW Ca2+ ions can enter the cell. and an association between those two synapses is formed. We still don t have LTP! Ca2+ ions entering the cell bind with the enzyme CaM- KII CaM-KII causes more AMPA receptors to to move to post-synaptic synaptic membrane. More AMPA receptors means it s easier to depolarize the cell in the future. 8

9 We still don t have LTP! Ca2+ ions entering the cell bind with the enzyme CaM- KII CaM-KII causes more AMPA receptors to to move to post-synaptic synaptic membrane. More AMPA receptors means it s easier to depolarize the cell in the future. For Ca2+ to enter the cell, NMDA receptors have to be activated by glutamate AND subjected to depolarization simultaneously. The fact that both these things must occur together means that NMDA receptors are coincidence detectors. Thus, they are crucial for LTP. 9

10 Perceptual Learning The ventral stream involved with object recognition, continues ventrally into the inferior temporal cortex. The dorsal stream involved with perception of the location of objects, continues dorsally into the posterior parietal cortex. The ventral stream is involved with the what of visual perception; the dorsal stream is involved with the where. Instrumental Conditioning Circuits responsible for instrumental conditioning begin in sensory association cortices and end in motor association cortex. 10

11 Instrumental Conditioning 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

12 What can possibly go wrong? Anterograde Amnesia: Amnesia for events occurring after the precipitating event. Retrograde Amnesia: Amnesia for events occurring before the precipitating event. The Medial Temporal Lobe: Crucial in the Declarative Memory System Damage to these areas usually results in anterograde amnesia: patients are unable to form new declarative memories. Can also result in retrograde amnesia: typically graded. Non-declarative memory is not affected. 12

13 H.M. Effects of Bilateral Medial Temporal Lobectomy Minor seizure beginning at age 10, major seizures beginning age 16 Severe, persistent seizure condition- not controlled with anticonvulsants By mid-20 s, condition was so severe he was unable to work Surgery at age 27: Bilateral medial temporal lobe resection. In HM, the amygdala, entorhinal and perirhinal cortices, and about two- thirds of the hippocampus were removed 13

14 What s wrong with H.M., and what does it tell us about functions of Hippocampus and MTL? 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

15 What s wrong with H.M., and what does it tell us about functions of Hippocampus and MTL? 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? Hippocampus is essential for the formation, but not the storage or retrieval,, of long-term declarative memory Memory depends on Hippocampus for a short duration Hippocampus does not mediate short-term term memory 15

16 What does H.M. tell us about role of Hippocampus and MTL? STM and LTM are distinctly separate H.M. is unable to move memories from STM to LTM, a problem with memory consolidation 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 Explicit memories conscious memories Implicit memories unconscious memories, as when H.M. shows the benefits of prior experience 16

17 Broca s Area and Patient Tan Lateralization of Function For many functions the hemispheres do not differ and where there are differences, these tend to be minimal Lateralization of function is statistical, not absolute! e.g. Right hemisphere has some language abilities 17

18 Lateralization of Function Left Hemisphere Language Even for deaf people! Words, letters Right Hemisphere Emotional Prosody Music Spatial ability Faces, patterns The details The big picture Language Language is not a unitary ability Production vs. Comprehension Production Requires having something to say, being able to associate that thing with words, and making the mouth move appropriately Comprehension Begins in the auditory system (detection and analysis of sounds) but there is a difference between recognizing a word and comprehending it 18

19 What can possibly go wrong? 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? 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

20 What can possibly go wrong? Broca s aphasia Typically function words are most compromised, with content words being relatively spared. Aphasias are a spectrum What can possibly go wrong? 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

21 What can possibly go wrong? Broca s aphasia: not ONLY a production problem! Anomia: a difficulty in finding words (in naming things). What can possibly go wrong? Broca s aphasia: not ONLY a production problem! Articulation difficulties: mouth motor movements are disfluent, so words are often mispronounced 21

22 What else can possibly go wrong? 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 Difficulty recognizing words Impaired comprehension (failure to grasp the meaning of words) Difficulty converting thoughts into meaningful words 22

23 Wernicke s area is also implicated in Pure Word Deafness Uncompromised recognition of non- speech sounds and intonation. Caused by disruption of auditory input to Wernicke s area, or damage to Wernicke s area itself Wernicke s Area Transcortical sensory aphasia Wernicke s aphasics can t understand the meaning of words or translate their thoughts into meaningful words. This seems to be due to trauma to the posterior language area. Damage to just this area often results in transcortical sensory aphasia. These patients can recognize words: they can repeat back what you say but can t make meaning. 23

24 Language Areas Conduction Aphasia The fact that transcortical aphasia patients can perform repetition suggests that there is a direct connection between Wernicke s area and Broca s area This is known as the arcuate fasciculus 24

25 Conduction Aphasia 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 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!) 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

26 Conduction aphasia Anomic aphasia Speech of anomic aphasics is fluent and grammatical, and their comprehension is fine but they appear to have difficulty finding the right words. Fluent anomia is caused by posterior lesions to the temporal or parietal lobes. Patients adopt circumlocutions: alternative ways of saying what they mean 26

27 What is an emotion? appraisal experience physiological response behavior Autonomic & Hormonal 4 ingredients of an emotion Appraisal or interpretation of some stimulus event, object, or thought- in terms of well-being Subjective experience or feeling e.g. Fear Physiological responses e.g. change in heart rate Overt or observable behaviors e.g. facial expressions, running away 27

28 Emotions as response patterns Three components of the emotional response: Behavioral component (e.g. muscle movements) Autonomic component (e.g. heart rate) Hormonal component (e.g. epinephrine) James-Lange Theory appraisal physiological response experience Stimulus triggers autonomic/skeletal response which then triggers emotion Implication: Autonomic/skeletal response is necessary for emotion 28

29 Cannon-Bard Theory appraisal physiological response experience Stimulus triggers autonomic/skeletal response and emotion Implication: Autonomic/skeletal response is independent of emotion behavior Darwin s Theory Expressions of emotion evolve from indicative behaviors If such signals are beneficial, communicative function will be enhanced (original function may be lost) Principle of antithesis Opposite messages are often signaled by opposite movements 29

30 Emotions and Facial Expression The meanings of facial expressions appear to be universal Originally, six primary emotions, but now ten are recognized (including contempt, embarrassment, guilt, interest) Naturally occurring expressions are usually variations or combinations of the basic ones Not all pleasant facial expressions are the same (e.g., pride vs. happiness) Facial Expressions Facial feedback hypothesis smiling really makes you happier! facial muscles influence emotional experience Rutledge & Hupka,

31 Two-factor Theory Schacter and Singer (1962) physiological response appraisal cognitive label experience Dutton & Aron (1974) 31

32 What is an emotion? appraisal experience physiological response Bottom-up AND Top-down influences!! The Limbic System Circuit implicated in crucial emotions/instincts: Feeding Fighting Fleeing Sexual behavior The four F s 32

33 Phineas Gage Extensive damage to medial prefrontal and orbitofrontal cortex Responsible for The balance Gage lacked the cortex necessary to inhibit his emotional responses But it is also possible to not have emotional responses at all if they lack access to the cortex! Damasio s s patient Elliott I I know this is horrible, I just don t feel the horror 33

34 Elliott Operation to remove tumor also severed connections between frontal cortex and limbic system Normal IQ Normal Memory Ability to do calculations and deductions but completely unable to function! Deprived of his feelings, he couldn t evaluate choices. The job of the cortex may be to prevent inappropriate responses rather than to produce appropriate ones! 34

35 Morality and the vmpfc Effects of vmpfc damage on morality 35

36 Communication of Emotions Several studies have found that damage to the amygdala impairs people s ability to recognize facial expressions of emotion, especially expressions of fear. Recognition of Emotions The rapid response suggests that visual information that the amygdala receives directly from the subcortical visual system (which conducts information very rapidly) permits it to recognize facial expressions of fear. High road ms Cortex Low road- 12 ms Thalamus Amygdala Emotional stimulus Emotional response 36

37 Recognition of Emotions We recognize other people s feelings by means of vision and audition seeing their facial expressions and hearing their tone of voice and choice of words. Many studies have found that the right hemisphere plays a more important role than the left hemisphere in comprehension of emotion. Recognition of Emotions Adolphs et al. (2000) discovered a possible link between somatosensation and emotional recognition. Examined the locations of brain damage in ~100 patients with localized brain lesions and correlated this information with the patients ability to recognize and identify facial expressions of emotions. They found that this ability was most compromised by damage to the somatosensory cortex of the right hemisphere. 37

38 Lateralization of Emotion Two theories Right-hemisphere hemisphere model the right hemisphere is dominant for all aspects of emotion Valence model the right hemisphere specializes in negative emotions, and the LH Both theories are probably too general 38