Network Dynamics Mediated by Synaptic Depression

Wednesday, January 21, 1998 - 11:00am - 12:00pm
Keller 3-180
John Rinzel (New York University)
Many synapses show depression in response to repeated activation. Multiple time scales (100s of msec to many sec) are reported for the depression and its recovery. We will review some models for depression and proposed effects in neuronal interaction dynamics (gain control, phasic responsiveness, direction selectivity, etc). An application to rhythmogenesis will be highlighted.

Spinal cord neuron populations execute synchronized rhythmic activity in isolated embryonic cords and in disinhibited cultures. The multimodal collective oscillations are infrequent episodic bursts of fast cycles (0.5 to 5 Hz). Synaptic coupling is primarily excitatory, and synaptic depression has been implicated as a possible rhythmogenic mechanism. We have developed a two-variable firing rate model in which cells spike tonically when stimulated. Synaptic depression accounts for the fast events - alternately allowing cells to mutually activate each other and then suppressing their interaction. By adding a slow modulatory variable, episodic behavior in the model can occur via several mechanisms.