PART 4: BEHAVIORAL PLASTICITY #20: LEARNING & MEMORY of a SIMPLE REFLEX in APLYSIA I F model system: sea hare ( Aplysia californica ) F behavior: the gill & siphon withdrawal reflex F cell biology: learning & memory F summary

F model system: sea hare ( Aplysia californica ) F behavior: the gill & siphon withdrawal reflex F cell biology: learning & memory F summary PART 4: BEHAVIORAL PLASTICITY #20: LEARNING & MEMORY of a SIMPLE REFLEX in APLYSIA I

F slow moving gastropod mollusk F phylum: Mollusca F order: tectibranchia F subclass: Opisthobranchia F genus: Aplysia, about 35 species F A. californica : cm, south Pacific waters F few (~ 20K) neurons, some very large & identifiable F  can associate neural function with behavior F circuitry, cell & molecular biology of learning SEA HARE ( Aplysia californica )

F gill & siphon withdrawal reflex F top view of A. californica F tactile stimuli  gill & siphon withdrawn under mantle & covered with parapodium F reliable behavior F > 30 yrs of study F neural mechanisms of learning SEA HARE ( Aplysia californica )

F we will focus on 2 main ideas in this chapter F non-associative vs associative learning F memory phases THE GILL & SIPHON WITHDRAWL REFLEX

F in very general terms, what can animals learn? 1. a single stimulus 2. temporal relationships among stimuli 3. influence of own behavior on #2 F different types of learning: F non-associative learning  #1 only F associative learning F Pavlovian or classical  #1 & 2 F operant or instrumental  #1, 2 & 3 THE GILL & SIPHON WITHDRAWL REFLEX

F study using Aplysia restrained in aquarium F tactile stimulation to siphon  gill retraction F repeat at 90s interval  habituation F electric shock stimulation to tail (or neck) F gill retraction restored  dishabituation THE GILL & SIPHON WITHDRAWL REFLEX

F study using Aplysia restrained in aquarium F tactile stimulation to siphon  gill retraction F repeat at 90s interval  habituation F electric shock stimulation to tail (or neck) F gill retraction restored  dishabituation F electric shock stimulation to tail in naive animals F gill retraction enhanced  sensitization F memory fairly short for all three types (min or hrs) F long-term forms can also be generated THE GILL & SIPHON WITHDRAWL REFLEX

F associative learning: classical or Pavlovian F US = tail shock F UR = rigorous siphon withdrawal F CS = siphon stimulus THE GILL & SIPHON WITHDRAWL REFLEX

F associative learning: classical or Pavlovian F US = tail shock F UR = rigorous siphon withdrawal F CS = siphon stimulus F training: US + CS F test: CR = rigorous siphon withdrawal THE GILL & SIPHON WITHDRAWL REFLEX

F associative learning: classical or Pavlovian F test with CS alone after training with: F US only  sensitization control F US + CS unpaired = stimulus control F US + CS paired = classical conditioned F learn siphon stimulus predicts tail shock THE GILL & SIPHON WITHDRAWL REFLEX

F associative learning: differential classical F US = tail shock F UR = rigorous siphon withdrawal F CS1 + = siphon (or mantle stimulation) paired F CS2 – = mantle (or siphon stimulation) unpaired THE GILL & SIPHON WITHDRAWL REFLEX

F associative learning: differential classical F US = tail shock F UR = rigorous siphon withdrawal F CS1 + = siphon (or mantle stimulation) paired F CS2 – = mantle (or siphon stimulation) unpaired F training: US + CS1 + paired, US + CS2 – unpaired F test: CR = rigorous siphon withdrawal THE GILL & SIPHON WITHDRAWL REFLEX

F associative learning: differential classical F test with CS1 or CS2 alone after training with: F CS1 + = siphon (or mantle stimulation) paired F CS2 – = mantle (or siphon stim.) unpaired F learn that CS + predicts tail shock THE GILL & SIPHON WITHDRAWL REFLEX

F associative learning: interstimulus interval F CS must precede US in training F 0.5 s in A. californica F no learning with backward conditioning THE GILL & SIPHON WITHDRAWL REFLEX

F long-term memory F short-term memory:  minutes / hours F long-term memory:  days / weeks F distributed (spaced) vs massed training is the key TIME MEMORY SPACED MASSED THE GILL & SIPHON WITHDRAWL REFLEX

F long-term memory in habituation F train: 4 days (T1-4) F test: 1 day (R1), 1 wk (R2), 3 wks (R3) THE GILL & SIPHON WITHDRAWL REFLEX

F long-term memory in habituation F train: 4 days (T1-4) F test: 1 day (R1), 1 wk (R2), 3 wks (R3) THE GILL & SIPHON WITHDRAWL REFLEX

F long-term memory in sensitization F train: 4 days (T1-4) F test: 1 day (R1), 1 wk (R2), 3 wks (R3) THE GILL & SIPHON WITHDRAWL REFLEX

F long-term memory in associative learning F data not shown THE GILL & SIPHON WITHDRAWL REFLEX

F functional architecture of withdrawal reflexes F ganglia & connectives F bilaterally symmetrical prs F abdominal ganglion important for reflex: F 1° sensory neurons F interneurons F motor neurons CELL BIOLOGY OF LEARNING & MEMORY

F functional architecture of withdrawal reflexes F neural circuit of reflex F ~ 20 sensory neurons  motor neurons F interneurons F excite F inhibit CELL BIOLOGY OF LEARNING & MEMORY

F functional architecture of withdrawal reflexes F neural circuit of reflex F ~ 20 sensory neurons  motor neurons F interneurons F excite F inhibit F focus on synapses CELL BIOLOGY OF LEARNING & MEMORY

F big +s for using Aplysia : F direct monitor of synaptic transmission... F of identified neurons... F in numerous different preparations... F to measure behavior CELL BIOLOGY OF LEARNING & MEMORY

F intact preparation F expose abdominal ganglion F gill & siphon withdrawal triggered & measured F simultaneous intracellular recordings CELL BIOLOGY OF LEARNING & MEMORY

F semi-intact preparation F separate organs with neurons F reliable recording CELL BIOLOGY OF LEARNING & MEMORY

F isolated abdominal gangion F direct access to all neural elements F mimic tactile stimulation with neural stimulation CELL BIOLOGY OF LEARNING & MEMORY

F cell culture F most reduced F examine properties of single synapses between sensory and motor neurons F reconstruct monosynaptic component of reflex CELL BIOLOGY OF LEARNING & MEMORY

F mechanistic analysis of sensitization – the synapse F synaptic facilitation F semi-intact preparation F electrically stimulate tail F  sensory to motor EPSP F presynaptic mechanism F  Ca ++ into neuron F  transmitter release F spike broadening CELL BIOLOGY OF LEARNING & MEMORY

F mechanistic analysis of sensitization – the synapse F synaptic facilitation F semi-intact preparation F serotonin application F  sensory to motor EPSP F serotonin blocker F prevents  sensory to motor EPSP (not shown) CELL BIOLOGY OF LEARNING & MEMORY

F mechanistic analysis of sensitization – biophysics F serotonin  sensory to motor EPSP F whole cell current: voltage clamp F single ion channel patch clamp F serotonin  outward K-current by... F prolonged closure of 2 S-current channels: F “serotonin-sensitive K current” (S current) F delayed K current F prevents repolarization of membrane F leads to spike broadening CELL BIOLOGY OF LEARNING & MEMORY

F mechanistic analysis of sensitization – molecular CELL BIOLOGY OF LEARNING & MEMORY

F mechanistic analysis of sensitization – molecular F synaptic facilitation F semi-intact preparation F inject cAMP 2 nd messenger F  sensory to motor EPSP CELL BIOLOGY OF LEARNING & MEMORY

F mechanistic analysis of sensitization – molecular F inject PKA catalytic subunit same result F phosphorylates (closes) K-channels F sensitization model incomplete… CELL BIOLOGY OF LEARNING & MEMORY

F mechanistic analysis of classical conditioning F presynaptic factors F similarities with sensitization F reflex facilitation of siphon withdrawal F induced by tail shock F facilitation amplified by temporal CS-US pairing F same (amplified) mechanism or not? CELL BIOLOGY OF LEARNING & MEMORY

F mechanistic analysis of classical conditioning F presynaptic factors F similarities with sensitization F reflex facilitation of siphon withdrawal F induced by tail shock F facilitation amplified by temporal CS-US pairing F same (amplified) mechanism or not? F test with differential conditioning paradigm CELL BIOLOGY OF LEARNING & MEMORY

F mechanistic analysis of classical conditioning F presynaptic factors F semi-intact preparation F CS1 = siphon (SN) F CS2 = mantle (SN) F US = tail shock CELL BIOLOGY OF LEARNING & MEMORY

F mechanistic analysis of classical conditioning F presynaptic factors F enhanced facilitation in paired training F  = paired vs unpaired F  = paired vs US alone F temporal pairing effect F activity-dependent presynaptic facilitation CELL BIOLOGY OF LEARNING & MEMORY

F mechanistic analysis of classical conditioning F presynaptic factors F differential synaptic facilitation results similar to behavioral experiments CELL BIOLOGY OF LEARNING & MEMORY

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