Functional relations between neighboring neurons of nucleus interpositus of the cat cerebellum.

In the nucleus interpositus (IP) of the cat cerebellum the response patterns to peripheral stimulation were recorded, and the interactions between electrophysiologically identified neurons were studied with cross correlation techniques. The response patterns were composed of excitation appearing with latencies of about 8 to 22 ms., separated and succeeded by phases of inhibitions. Four basic types of interneuronal connectivities were observed: 1) intranuclear excitation, 2) shared input from a common source, 3) intranuclear inhibition, and 4) stimulus coordinated firing. Shared input appeared in all combinations of paired neurons and extended for a distance from 300 microns up to 1000 microns. Intranuclear excitation as well as inhibitory synaptic connection occurred mainly in combinations between interneurons and efferent neurons. Stimulus coordinated firing of paired neurons was found in almost the entire extent of the nucleus interpositus.