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Updated: Jun 9, 2025

Parallel Measurement of Circadian Clock Gene Expression and Hormone Secretion in Human Primary Cell Cultures
Published on: November 11, 2016
The Circadian Brain and Cognition
Christian Cajochen1,2, Christina Schmidt3,4
1Research Cluster Molecular and Cognitive Neurosciences, Department of Biomedicine, University of Basel, Basel, Switzerland.
Abstract:
Circadian rhythms are inherent to living organisms from single cells to humans and operate on a genetically determined cycle of approximately 24 hours. These endogenous rhythms are aligned with the external light/dark cycle of the Earth's rotation and offer the advantage of anticipating environmental changes. Circadian rhythms act directly on human cognition and indirectly through their fundamental influence on sleep/wake cycles. The strength of the circadian regulation of performance depends on the accumulated sleep debt and the cognitive domain, and it has been suggested to involve the activation of ascending arousal systems and their interaction with attention and other cognitive processes. In addition, attention-related cortical responses show extensive circadian rhythms, the phases of which vary across brain regions. This review discusses the impact of the circadian system on sleep/wake regulation and cognitive performance. It further addresses the health implications of circadian disruption, particularly in relation to mental and neurological disorders.
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