Fig. 5.

Three examples of single unit activity recordings. Single unit circadian activity patterns are narrow and are found throughout the circadian cycle mainly during the day. Neuronal discharge of single units were isolated on the basis of cluster analysis. (Left) Neuronal activity was determined in 2-min bins and plotted in Hertz as a function of CT. (Right) The autocorrelogram was computed for each single unit over the whole recording period and show a clear refractory period around the zero interval. It is apparent that individual SCN neurons show asynchronous circadian activity rhythms with short durations of electrical activity.