Integrity of the circadian clock determines regularity of high-frequency and diurnal LFP rhythms within and between brain areas.

Circadian clocks control most physiological processes of many species. We specifically wanted to investigate the influence of environmental and endogenous rhythms and their interplay on electrophysiological dynamics of neuronal populations. Therefore, we measured local field potential (LFP) time series in wild-type and Cryptochrome 1 and 2 deficient (Cry1/2) mice in the suprachiasmatic nucleus and the nucleus accumbens under regular light conditions and constant darkness. Using refined descriptive and statistical analyses, we systematically profiled LFP time series activity. We show that both environmental and endogenous rhythms strongly influence the rhythmicity of LFP signals and their frequency components, but also shape neuronal patterns on much smaller time scales, as neuronal activity in Cry1/2 mice is significantly less regular but at each time more synchronous within and between brain areas than in wild-type mice. These results show that functional circadian rhythms are integral for both circadian and non-circadian coordination of neuronal ensemble dynamics.