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PART 4: BEHAVIORAL PLASTICITY #21: LEARNING & MEMORY of a SIMPLE REFLEX in APLYSIA II. model system: sea hare ( Aplysia californica ) behavior: the gill & siphon withdrawal reflex even more cell biology: learning & memory summary. PART 4: BEHAVIORAL PLASTICITY
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PART 4: BEHAVIORAL PLASTICITY #21: LEARNING & MEMORY of a SIMPLE REFLEX in APLYSIA II • model system: sea hare (Aplysia californica) • behavior: the gill & siphon withdrawal reflex • even more cell biology: learning & memory • summary
PART 4: BEHAVIORAL PLASTICITY #21: LEARNING & MEMORY of a SIMPLE REFLEX in APLYSIA II • model system: sea hare (Aplysia californica) • behavior: the gill & siphon withdrawal reflex • even more cell biology: learning & memory • summary
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of classical conditioning • convergence of CS & US in sensory neuron • adenylyl cyclase (AC) = coincidence detector? • sensitization: • Ca++ channels closed • Ca++not bound to calmodulin • calmodulin not bound to AC • some cAMP ...
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of classical conditioning • convergence of CS & US in sensory neuron • adenylyl cyclase (AC) = coincidence detector? • associative learning: • Ca++ channels open • Ca++ bound to calmodulin • calmodulin bound to AC • lots of cAMP ...
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of classical conditioning • postsynaptic factors • glutamate, excitatory transmitter • activates N-methyl-D-aspartate (NMDA) receptor
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of classical conditioning • postsynaptic factors • glutamate, excitatory transmitter • activates N-methyl-D-aspartate (NMDA) receptor • no signal... • NMDA channel closed • no Ca++ enters cell
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of classical conditioning • postsynaptic factors • glutamate, excitatory transmitter • activates N-methyl-D-aspartate (NMDA) receptor • signal... • glutamate binds to receptor • postsynaptic membrane depolarizes • postsynaptic neuron fires • test this model?
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of classical conditioning • postsynaptic factors • differential conditioning
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of classical conditioning • postsynaptic factors • differential conditioning • aminophosphonovalerate (APV) block of NMDA receptor…
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of classical conditioning • postsynaptic factors • differential conditioning • block NMDA receptor with APV during training
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of classical conditioning • postsynaptic factors • differential conditioning • block NMDA receptor with APV during training • associative synaptic facilitation
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of classical conditioning • postsynaptic factors • differential conditioning • block NMDA receptor with APV during training • associative synaptic facilitation • NMDA receptor necessary
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of classical conditioning • postsynaptic factors • differential conditioning • same result during training if • postsynaptic neuron: • hyperpolarized • Ca++ blocked • presynaptic neuron: • PKA blocked • Ca++
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of classical conditioning • postsynaptic factors • implication that the postsynaptic neuron communicates with the presynaptic neuron • retrograde (backward) signaling • evidence (not shown) – associative facilitation mechanism in postsynaptic neuron changes signaling properties in the presynaptic neuron • neurons communicate in both directions • but... what is the signal?
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of classical conditioning • revised model • 2 sites of CS-US coincidence • presynaptic AC
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of classical conditioning • revised model • 2 sites of CS-US coincidence • presynaptic AC • postsynaptic NMDA receptor gated channels
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of classical conditioning • revised model • 2 sites of CS-US coincidence • presynaptic AC • postsynaptic NMDA receptor gated channels • retrograde signal (hypothetical)
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • long-term synaptic facilitation in sensory neurons • terminology: • long-term memory (LTM) behavioral measure • long-term facilitation (LTF) physiological measure
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • long-term synaptic facilitation in sensory neurons • distributed sensitization training
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • long-term synaptic facilitation in sensory neurons • distributed sensitization training: • siphon withdrawal
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • long-term synaptic facilitation in sensory neurons • distributed sensitization training • siphon withdrawal • sensory EPSPs
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • long-term synaptic facilitation in sensory neurons • distributed sensitization training • siphon withdrawal • sensory EPSPs • S-current (data not given)
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • long-term synaptic facilitation in sensory neurons • distributed sensitization training • siphon withdrawal • sensory EPSPs • S-current • serotonin-induced presynaptic transmitter release (data not given)
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • long-term synaptic facilitation in sensory neurons • distributed sensitization training • siphon withdrawal • sensory EPSPs • S-current • serotonin-induced presynaptic transmitter release (data not given) • presynaptic neuronal plasticity
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • long-term synaptic facilitation in sensory neurons • distributed sensitization training • serotonin substitutes for tail shock @ sensory • cell body LTF • terminal STF
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • long-term synaptic facilitation in sensory neurons • distributed sensitization training • serotonin substitutes for tail shock @ sensory • cell body LTF • terminal STF
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • long-term synaptic facilitation in sensory neurons • serotonin induces • LTF • intracellular signal • protein synthesis (?) • neural plasticity (?) • STF • locally @ synapse
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • long-term synaptic facilitation in sensory neurons • protein synthesis (?) • transcription • translation • transport synapses
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • long-term synaptic facilitation in sensory neurons • protein synthesis inhibited by blockers • also block LTF • during serotonin application only • not before or after... • narrow temporal window
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • long-term synaptic facilitation in sensory neurons • protein synthesis inhibited by blockers • also block LTF • during serotonin application only • not before or after... • narrow temporal window • no block of STF
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • long-term synaptic facilitation in sensory neurons • protein synthesis inhibited by blockers • also block LTF • during serotonin application only • not before or after... • narrow temporal window • no block of STF • ... and does block LTM (behavior) • protein synthesis necessary for LTM
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • long-term sensitization / serotonin treatments molecular changes in sensory neurons: • persistent phosphorylation of existing proteins • synthesis of new proteins • growth of sensory neurons... neural plasticity
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • long-term sensitization / serotonin treatments molecular changes in sensory neurons: • growth of sensory neurons... neural plasticity • visual examination • axonal processes, branching, varicosities
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • long-term sensitization / serotonin treatments molecular changes in sensory neurons: • growth of sensory neurons... neural plasticity • visual examination • axonal processes, branching, varicosities
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • long-term sensitization / serotonin treatments molecular changes in sensory neurons: • growth of sensory neurons... neural plasticity • model for synaptic restructuring / plasticity • varicosities • terminal active zones • opposite for habituation
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • long-term sensitization / serotonin treatments molecular changes in sensory neurons: • growth of sensory neurons... neural plasticity • model for synaptic restructuring / plasticity • varicosities • terminal active zones • long-term increase in synaptic transmission • what are the molecular mechanisms?
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • molecular induction of LTF in sensory neurons • cAMP pathway implicated: • cAMP injection ... S-current • PKA inhibitors ... block serotonin-induced LTF • serotonin application ... PKA catalytic subunit cytoplasmic nuclear • activity of genes: • immediate early (IEG), transcription factors • late-responsive, leave nucleus
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • molecular induction of LTF in sensory neurons • cAMP pathway implicated: • cAMP response elements (CREs) on DNA • CRE binding protein (CREB) • phosphorylated by PKA... CREBs IEGs • IEGs late-responsive genes
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • molecular induction of LTF in sensory neurons • single training event some PKA, STF • distributed training more PKA... nucleus, LTF
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • molecular induction of LTF in sensory neurons • competition studies using injected CRE sequences block CREB binding & LTF
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • molecular induction of LTF in sensory neurons • competition studies using injected CRE sequences block CREB binding & LTF
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • molecular induction of LTF in sensory neurons • competition studies using injected CRE sequences block CREB binding & LTF • enhanced CREB + 1 serotonin application • LTF • structural enhancement • CREB essential for LTF & LTM • similar findings in Drosophila (next chapter)
CELL BIOLOGY OF LEARNING & MEMORY • mechanistic analysis of long-term memory • LTF molecular model • what proteins? • how do they work? • other 2nd messenger cascades? • homology (flies, mice)
CELL BIOLOGY OF LEARNING & MEMORY • middle-term memory... read the section on your own
SUMMARY • defensive withdrawal reflex after stimulation (CS) of • siphon, mantle, gill • shows non-associative learning properties • habituation, dishabituation, sensitization • sensitization: reflex with preceding tail shock • associative learning • reflex (CS) + paired shock (US) • differential conditioning = CS1+ + US, CS2– • distributed training long-term memory
SUMMARY • tail shock sensitization • interneuron serotonin release sensory neuron • K current flow (out of cell) • spike broadening • synaptic facilitation • cAMP cascade mediated • sensory neuron transmitter release
SUMMARY • classical conditioning • interneuron serotonin release sensory neuron • tail shock US responses augmented by concurrent CS signal... • activity-dependent presynaptic facilitation • postsynaptic process, NMDA receptor in motor neuron
SUMMARY • long-term memory • dispersed training • protein synthesis-dependent • cAMP & CREB IEGs • IEGs late-response genes • proteins neuron terminals • neuronal plasticity