Neurobiology of sleep and circadian rhythmsFeb 9, 2026

Rethinking the daily biological clock in mammals

Circadian Biology Weekly Brief ↗PubMed ↗DOI ↗

Updated Jun 27, 2026

Abstract

Essence

Mammalian circadian organization is presented as a coupled network shaped by temporal niches rather than a simple central-versus-distributed clock.

Evidence

This review synthesizes mammalian and comparative non-mammalian research on coupling across cells, tissues, and organs in circadian networks.

Caveat

The abstract describes broad organizing principles from comparative evidence rather than new experiments, so it does not test a single mammalian mechanism or intervention.

Simplified

A circadian clock enables an organism to occupy a particular temporal niche, and the evolutionary pressures associated with that temporal niche in turn shape the organization of the circadian network in which the clock is embedded. Although circadian organization has often been dichotomized into centralized and distributed systems, our modern understanding of circadian networks reveals a more complex organization that cannot be captured by this simple dichotomy. In this review, we examine how coupling between nodes of the circadian network (from cells, to tissues, to organs) gives rise to coherent circadian organization in mammals. We further highlight how comparative research on non-mammalian organisms reveals conserved and divergent strategies for circadian coupling that inform general principles of circadian network function across species.