Divergence from statistical independence in specified clusters of adjacent neuronal spike train intervals before and after ethanol state changes

Abstract

In order to test the inffuence of drug-induced state changes on serial ordering of interaction potential intervals, we evaluated divergence from statistical independence of specific “clusters” of various numbers of adjacent intervals. Such divergence, which was highly significant statistically, was noted using two different methods, one based on relative interval duration, and the other based on categorizing intervals as to short, medium, or long. Before ethanol. significant divergence was seen for clusters of as many as 5–6 adjacent intervals, and this same degree of serial ordering was seen after ethanol. While the apparent cluster length remained unchanged by ethanol, the specific clusters which contributed most to the statistical significance were generally not the same after ethanol. This suggests that neurons process intervals as “clusters” of a given length but that specific “clusters” may be important “information carriers” in the nervous system. The methodology outlined herein may allow us to identify these important “clusters.”