Pattern generation in the lobster (Panulirus) stomatogastric ganglion

Abstract

The principles governing neural pattern generation were studied in the pyloric subsystem of lobster stomatogastric ganglion. Quantitative estimates were obtained for repetitive-firing and synaptic-interaction parameters for use in developing quantitative theories (including computer models) of ganglion functioning. 1. The neurons fired tonically to depolarizing current steps, adapting to about 30% of initial frequency along a compound exponential with time-constants around 0.3 and 3.5 s. 2. Both initial and final firing frequencies to depolarizing current steps were approximately logarithmic with current over a substantial current range (2–10 nA). 3. Post-hyperpolarization rebound was exhibited by all cell types. Its magnitude was a linear function of current in some but not all cases. In simple cases build-up followed a compound exponential with time constants similar to those for adaptation. 4. Synaptic potentials were of two general types: sharprising (t_peak≃12 ms) and rounded (t_peak≃80 ms). 5. Effective synaptic strengths were measured between neuron types. In some cases the strengths were sufficient to expect complete shut-off of moderate activity in postsynaptic elements by moderate activity in presynaptic elements. 6. Certain properties of the system enhance switch-like on/off activity in each cell, which could contribute to burst generation and to appropriate phasing of bursts in the activity cycle.