Integration of neural plasticity • Multiple mechanisms per synapse • Multiple synapses per cell • Multiple cells per function • Examples – Tritonia escape response – Aplysia gill withdrawal reflex – Leech central pattern generator – Autonomic control of hypertrophy
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Integration of neural plasticity Multiple mechanisms per synapse Multiple synapses per cell Multiple cells per function Examples –Tritonia escape response.
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Integration of neural plasticity
• Multiple mechanisms per synapse
• Multiple synapses per cell
• Multiple cells per function
• Examples– Tritonia escape response– Aplysia gill withdrawal reflex– Leech central pattern generator– Autonomic control of hypertrophy
• Rhythmic assembly of neurons– Coordinate cyclic movement patterns
• Flexion-extension• Parystalsis
– Self-organizing, independent of external feedback
• Hierarchical• Entrainment
– Sensory feedback– Higher neural process
CPG Organization
• Leech swimming by dorso-ventral flexion
• Independent control of 32 segments
Motorneurons
CP
G
Friesen et al, 1976
CPG signal propagation
• Generalized “descending” excitation
• Segmental coordination by inhibition
Friesen et al, 1976
Inhibitory connections run opposite direction of signal propagation
Coordination• Intersegmental
– Parallel PA inhibition as within segment– Conduction delay between segments
Coordination
• Sensory feedback– Nervous system needs state information– Subject to habituation, sensitization, etc
Gossard et al, 1994
PSPs in LG or sol motorneuron due to synergist afferent.•IPSP in “resting” state•EPSP after dopamine
This is a monosynaptic connection. Reversal with dopamine suggests that some dopaminergic interneuron changes the character of state feedback. EPSPs would extend the flexion half-center; IPSPs would shorten it.