Slow rhythmic activity of caudate neurons in the cat: Statistical analysis of caudate neuronal spike trains

Abstract

Spike trains of caudate neurons initially having mean interspike intervals of less than 4 ms were analyzed with progressive administration of pentobarbital (5 to 20 mg/kg). Among the neurons investigated, 77% ( N = 79) showed evidence of a rhythmic basis of their activity in first-order interspike interval histograms and/or autocorrelation histograms in the course of becoming silent due to progressive administration of pentobarbital. Although the rhythmicies of given units varied depending on the level of anesthesia the most prominent cycle was almost always within the range of 200 to 320 ms; the majority were not discernable on visual inspection of the spike trains. Cortical stimuli reset the cycle. Cross-correlation histograms constructed from pairs of caudate neurons provided some evidence that their spontaneous firing was mutually inhibited. The possibility that the rhythmicities might arise from such mutual inhibition of spontaneously firing caudate neurons is discussed.