PART 4: BEHAVIORAL PLASTICITY #20: LEARNING & MEMORY of a SIMPLE REFLEX in APLYSIA I
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Transcript of 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
model system: sea hare (Aplysia californica) behavior: the gill & siphon withdrawal reflex cell biology: learning & memory summary
PART 4: BEHAVIORAL PLASTICITY#20: LEARNING & MEMORY of a SIMPLE
REFLEX in APLYSIA I
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
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gill & siphon withdrawal reflex top view of A. californica tactile stimuli gill & siphon withdrawn under mantle & covered with parapodium reliable behavior 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
SEA HARE ( Aplysia californica)
we will focus on 2 main ideas in this chapter non-associative vs associative learning memory phases
THE GILL & SIPHON WITHDRAWL REFLEX
in very general terms, what can animals learn?1. a single stimulus2. temporal relationships among stimuli3. 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
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
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
THE GILL & SIPHON WITHDRAWL REFLEX
associative learning: classical or Pavlovian US = tail shock UR = rigorous siphon withdrawal CS = siphon stimulus
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
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
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
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
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
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
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
TIME
MEM
ORYSPACED
MASSED
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)
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)
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)
THE GILL & SIPHON WITHDRAWL REFLEX
long-term memory in associative learning data not shown
THE GILL & SIPHON WITHDRAWL REFLEX
functional architecture of withdrawal reflexes ganglia & connectives bilaterally symmetrical prs abdominal ganglion
important for reflex: 1° sensory neurons interneurons motor neurons
CELL BIOLOGY OF LEARNING & MEMORY
functional architecture of withdrawal reflexes neural circuit of reflex
~ 20 sensory neurons motor neurons interneurons
excite inhibit
CELL BIOLOGY OF LEARNING & MEMORY
functional architecture of withdrawal reflexes neural circuit of reflex
~ 20 sensory neurons motor neurons interneurons
excite inhibit
focus onsynapses
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
CELL BIOLOGY OF LEARNING & MEMORY
intact preparation expose abdominal ganglion gill & siphon withdrawal triggered & measured simultaneous intracellular recordings
CELL BIOLOGY OF LEARNING & MEMORY
semi-intact preparation separate organs with neurons reliable recording
CELL BIOLOGY OF LEARNING & MEMORY
isolated abdominal gangion direct access to all neural elements mimic tactile stimulation with neural stimulation
CELL BIOLOGY OF LEARNING & MEMORY
cell culture most reduced examine properties of single synapses between
sensory and motor neurons reconstruct monosynaptic component of reflex
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
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)
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
CELL BIOLOGY OF LEARNING & MEMORY
mechanistic analysis of sensitization – molecular
CELL BIOLOGY OF LEARNING & MEMORY
mechanistic analysis of sensitization – molecular synaptic facilitation semi-intact preparation inject cAMP 2nd messenger sensory to motor EPSP
CELL BIOLOGY OF LEARNING & MEMORY
mechanistic analysis of sensitization – molecular inject PKA catalytic
subunit same result phosphorylates
(closes) K-channels
sensitization modelincomplete…
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?
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
CELL BIOLOGY OF LEARNING & MEMORY
mechanistic analysis of classical conditioning presynaptic factors
semi-intact preparation CS1 = siphon (SN) CS2 = mantle (SN) US = tail shock
CELL BIOLOGY OF LEARNING & MEMORY
mechanistic analysis of classical conditioning presynaptic factors
enhanced facilitation inpaired training = paired vs unpaired = paired vs US alone
temporal pairing effect activity-dependent presynaptic facilitation
CELL BIOLOGY OF LEARNING & MEMORY
mechanistic analysis of classical conditioning presynaptic factors
differential synaptic facilitation results similar to behavioral experiments
CELL BIOLOGY OF LEARNING & MEMORY
BREAK