Interneuronal functional associations in the sensorimotor cortex of dogs.

The interneuronal functional associations were studied in two dogs with Nichrome semi-microelectrodes implanted into the deep layers of the motor and somatosensory regions of the cerebral cortex using the method of cross-correlation analysis. For this purpose the impulse activity of individual neurons was distinguished by form from the background multineuronal activity using the spike recognition technique. Values of a 0.5 and 1 msec-wide bin, and thereafter with a 1 msec step up to 40 msec, were used to plot the cross-interval histograms. The maximal analysis epoch was 2000 msec. The cross-interval associations were monotypal in character; they all presented fairly narrow extrema which were clearly distributed across three time ranges: short-latency associations up to 10 msec; associations with a medium latency up to 80 msec; and associations with late delays, greater than 80 msec. The fairly narrow peak of the association, especially in the case of associations with late delays, was a very difficult phenomenon to explain from the point of view of traditional theoretical perspectives. It is hypothesized that a mechanism exists in the cortex which is responsible for strictly synchronized and highly efficient synaptic transmission.