Chronotype influences fMRI derived resting-state connectivity patterns.

Abstract We investigated the influence of circadian rhythmicity and wake-up time on fMRI (functional Magnetic Resonance Imaging) derived resting-state data in 15 subjects by evaluating the time course of 20 brain connectivity patterns over 8h (4 sessions). For each subject, we determined the chronotype, which describes the relationship between the individual circadian rhythm and the local time. We detected highly significant correlations (r=0.82-0.9; p(corr) 0.00125). We conclude that chronotype generally influences fMRI derived resting-state connectivity patterns, but not necessarily resting-state neural activity. We hypothesize that the association between chronotype and resting-state connectivity patterns is primarily based on circadian rhythms in cardiovascular and respiratory functions, which both may essentially account for the signal time courses measured with fMRI.