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PART 4: BEHAVIORAL PLASTICITY #20: LEARNING & MEMORY of a SIMPLE REFLEX in APLYSIA I

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

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PART 4: BEHAVIORAL PLASTICITY #20: LEARNING & MEMORY of a SIMPLE REFLEX in APLYSIA I

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

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

  3. SEA HARE ( Aplysia californica) • slow moving gastropod mollusk • phylum: Mollusca • order: tectibranchia • subclass: Opisthobranchia • genus: Aplysia, about 35 species • A. californica: 15-30 cm, south Pacific waters • few (~ 20K) neurons, some very large & identifiable •  can associate neural function with behavior • circuitry, cell & molecular biology of learning

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( Aplysia californica) • gill & siphon withdrawal reflex • top view of A. californica • tactile stimuli  gill & siphon withdrawn under mantle & covered with parapodium • reliable behavior • 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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  32. CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of sensitization – molecular

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

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

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

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

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

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

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

  40. BREAK

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