Neurobiology of Circadian and Interval Timing

Abstract

Temporal processing in the brain is fundamental to environmental adaptation in humans and other animals. Biological timing ranges from the microsecond scale (e.g. sound localisation) to seasonal frequencies (such as reproductive cycles). Two of the main scales of biological timing ubiquitous in most organisms are interval timing (seconds‐to‐minutes range) and circadian timing (24 h range). Interval timing is crucial to learning, memory, decision‐making and other cognitive tasks, whereas circadian timing is essential for the regulation of several physiological and behavioural functions. Several brain areas, circuits and neuromodulators that are critical to temporal processing have now been identified. However, with the exception of the circadian system, the genetic and molecular machinery that regulates biological clocks has not been systematically examined. As a consequence, the molecular basis of these two temporal mechanisms is currently the subject of intense research, as well as their possible relationship. Key Concepts Biological timing (from microseconds to seasonal cycles) is fundamental for survival and optimal goal reaching in humans and other animals. Circadian timing (24 h) and interval timing (hundreds of milliseconds to minutes) are ubiquitous in nature and are required for normal physiology and behaviour. Dopamine metabolism in the striatum is critical for interval timing, and it is also the subject of circadian control. Circadian and interval timing may share some common pathways, including dopamine metabolism. Circadian and interval timing are seriously disrupted in human pathologies with dopamine dysfunction.