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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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slide1

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
slide2

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
slide3

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 ...
slide4

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 ...
slide5

CELL BIOLOGY OF LEARNING & MEMORY

  • mechanistic analysis of classical conditioning
  • postsynaptic factors
    • glutamate, excitatory transmitter
    • activates N-methyl-D-aspartate (NMDA) receptor
slide6

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
slide7

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?
slide8

CELL BIOLOGY OF LEARNING & MEMORY

  • mechanistic analysis of classical conditioning
  • postsynaptic factors
    • differential conditioning
slide9

CELL BIOLOGY OF LEARNING & MEMORY

  • mechanistic analysis of classical conditioning
  • postsynaptic factors
    • differential conditioning
    • aminophosphonovalerate

(APV) block of NMDA receptor…

slide10

CELL BIOLOGY OF LEARNING & MEMORY

  • mechanistic analysis of classical conditioning
  • postsynaptic factors
    • differential conditioning
    • block NMDA receptor with APV during training
slide11

CELL BIOLOGY OF LEARNING & MEMORY

  • mechanistic analysis of classical conditioning
  • postsynaptic factors
    • differential conditioning
    • block NMDA receptor with APV during training
    • associative synaptic facilitation 
slide12

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
slide13

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++ 
slide14

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?
slide15

CELL BIOLOGY OF LEARNING & MEMORY

  • mechanistic analysis of classical conditioning
  • revised model
    • 2 sites of CS-US coincidence
      • presynaptic AC
slide16

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

slide17

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)

slide18

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
slide19

CELL BIOLOGY OF LEARNING & MEMORY

  • mechanistic analysis of long-term memory
  • long-term synaptic facilitation in sensory neurons
    • distributed sensitization training
slide20

CELL BIOLOGY OF LEARNING & MEMORY

  • mechanistic analysis of long-term memory
  • long-term synaptic facilitation in sensory neurons
    • distributed sensitization training:
      • siphon withdrawal 
slide21

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 
slide22

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)

slide23

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)

slide24

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
slide25

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
slide26

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
slide27

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
slide28

CELL BIOLOGY OF LEARNING & MEMORY

  • mechanistic analysis of long-term memory
  • long-term synaptic facilitation in sensory neurons
    • protein synthesis (?)
      • transcription
      • translation
      • transport  synapses
slide29

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
slide30

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
slide31

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
slide32

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
slide33

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

slide34

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

slide35

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
slide36

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?
slide37

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
slide38

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
slide39

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
slide40

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 
slide41

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 
slide42

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)
slide43

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)
slide44

CELL BIOLOGY OF LEARNING & MEMORY

  • middle-term memory... read the section on your own
slide45

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
slide46

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
slide47

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
slide48

SUMMARY

  • long-term memory
    • dispersed training
    • protein synthesis-dependent
    • cAMP & CREB  IEGs
    • IEGs  late-response genes
    • proteins  neuron terminals
    • neuronal plasticity
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