Behavioral neuroscienceApr 30, 2014

How activity levels influence daily biological rhythms in mammals

Circadian Biology Weekly Brief ↗PubMed ↗DOI ↗

Updated Mar 21, 2026

Abstract

Nonphotic inputs to the circadian clock can significantly influence its timing.

Circadian rhythms in mammals are primarily synchronized by light-dark cycles, but behavioral arousal can also reset these rhythms.
The suprachiasmatic nucleus (SCN) is the brain region responsible for receiving light and non-light signals to adjust circadian rhythms.
Interactions between light and nonphotic stimuli in resetting the circadian clock are complex and not fully understood.
Nonphotic effects on circadian timing may impact experimental designs in behavioral neuroscience.
Understanding nonphotic inputs could offer new strategies for resetting or strengthening human circadian rhythms.

Simplified

Circadian rhythms in most mammals are synchronized to local time by phase and period resetting actions of daily light-dark cycles on a retino-recipient, light-entrainable circadian pacemaker, the suprachiasmatic nucleus (SCN). The SCN receives input from other brain regions, some of which mediate the phase and period resetting actions of behavioral arousal on circadian rhythms. We review historical milestones in the discovery of so-called "nonphotic" circadian clock resetting induced by environmentally stimulated arousal, or by feedback from clock-controlled rest-activity cycles. Topics include species generality, interactions between concurrent or successive photic and nonphotic inputs to the circadian clock, neural pathways, neurotransmitters, and clock cell responses that mediate resetting by behavioral arousal. The role of behavioral inputs to the circadian clock in determining the phase of entrainment to local time in natural environments is not well understood. Nonetheless, nonphotic effects are of sufficient magnitude to raise issues for the design of experiments in behavioral neuroscience (any procedure that is sufficiently arousing may alter the timing of circadian clocks that regulate dependent variables of primary interest). Nonphotic inputs to the clock may be exploited in strategies to reset or strengthen circadian rhythms in humans.

Full Text

Full text is available at the source.

View Full Text ↗

How activity levels influence daily biological rhythms in mammals

Abstract

Full Text

You found one interesting study. We’ll send the next 7.

What Lands in Your Inbox Each Week:

Recent issues from the circadian biology brief

Abstract

Full Text

Related papers

You found one interesting study. We’ll send the next 7.

What Lands in Your Inbox Each Week:

Recent issues from the circadian biology brief