Circadian Timing: from Genetics to Behavior

AGOSTINO P.V.; BUSSI I.L.; CALDART C.S.

Timing and Time Perception: Procedures, Measures, and Applications

BRILL

Lugar: Leiden; Año: 2018;

Biological clocks involve specialized timing mechanisms that allow organisms to keep synchronized with their environment. Among them, the circadian system regulates most physiological and behavioral functions with periods close to 24-h, from sleep/wake cycles in mammals to growth and photosynthesis in plants. The circadian clock is reset by external cues, being the most important in mammals the light/dark cycle. In addition, the circadian clock provides a temporal framework for cognitive function in diverse organisms. In particular, alertness, reaction time, memory, mood- and reward-related behaviors are regulated by the circadian clock. This timing system allows anticipatory responses of biological functions prior to periodic changes of the environment. At the molecular level, daily timekeeping is mainly driven by transcriptional?translational feedback loops, where rhythmic expression of clock gene products regulates the expression of associated genes in approximately 24-h cycles. The specific transcriptional components differ between phylogenetic groups. Invertebrate models, such as the insect Drosophila melanogaster, or the mollusks Aplysia and Lymnaea, have proven invaluable tools for identification of highly conserved molecular processes in circadian physiology. In mammals, endogenous oscillators with hierarchical organization, including a master clock located in the hypothalamic suprachiasmatic nuclei (SCN) of the brain, synchronize 24-h functions in different tissues. In this chapter we cover several aspects of circadian rhythms, including regulation of complex cognitive processes. We will include some recent findings regarding the molecular and cellular composition of the circadian timing system and discuss its implications for the temporal coordination of biological functions. Diverse tasks, methodologies, and data analyses related to circadian rhythms will be revised and explained. Finally, we provide Matlab scripts with some tools that allow analyzing circadian rhythmicity.