Memory and the circadian system: Identifying candidate mechanisms by which local clocks in the brain may regulate synaptic plasticity

• Published in: Neuroscience and biobehavioral reviews 2020-11, Vol.118, p.134-162
• Main Authors: Hartsock, Matthew J., Spencer, Robert L.
• Format: Article
• Language: English
• Subjects: Circadian rhythms; Clock genes; Local clocks; Memory; Metaplasticity; Synaptic plasticity
• ISSN: 0149-7634; 1873-7528
• DOI: 10.1016/j.neubiorev.2020.07.023

•Memory function is fundamentally regulated by the circadian system.•Cellular clocks are a genetic timekeeping mechanism underlying circadian rhythms.•Cellular clocks are found locally in brain regions that support memory.•Local clocks in the brain directly regulate mechanisms of synaptic plasticity.•Local clocks may optimize memory phasing by modulating neuronal plastic capacity. The circadian system is an endogenous biological network responsible for coordinating near-24-h cycles in behavior and physiology with daily timing cues from the external environment. In this review, we explore how the circadian system regulates memory formation, retention, and recall. Circadian rhythms in these memory processes may arise through several endogenous pathways, and recent work highlights the importance of genetic timekeepers found locally within tissues, called local clocks. We evaluate the circadian memory literature for evidence of local clock involvement in memory, identifying potential nodes for direct interactions between local clock components and mechanisms of synaptic plasticity. Our discussion illustrates how local clocks may pervasively modulate neuronal plastic capacity, a phenomenon that we designate here as circadian metaplasticity. We suggest that this function of local clocks supports the temporal optimization of memory processes, illuminating the potential for circadian therapeutic strategies in the prevention and treatment of memory impairment.