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The neuronal circuit underlying rapid abdominal flexion in response to phasic tactile stimulation comprises identified afferents, interneurons of two orders, a decision unit, and several motor neurons. The circuit is organized hierarchically as a " cascade" in which electrical synapses predominate at higher levels. Behavioral habituation results from lability at chemical junctions early in the pathway.

Predictions from the cable model and equations for field potentials generated by single neurons are computed and compared with extra cellular recordings from synaptically activated cerebellar Purkinje cell dendrites. Neither theory predicts the results, nor does the expermental situation satisfy the assumptions of either theory. Theoretical calculations from a recent formulation developed by Rall compare favorably with potentials recorded by others authors. A pplications of these formulations are discussed.