Circadian rhythms pervade all aspects of mammalian physiology and behaviour, providing a near 24 h temporal architecture for all major brain and body systems. Mammalian chronobiology research has focused on nocturnal laboratory rodent models, and this has yielded valuable insight into the neural basis of circadian timekeeping. This has identified the suprachiasmatic nuclei (SCN) as the dominant circadian pacemaker and characterised its neurophysiology, neurochemistry, and potential mechanisms of behavioural control. However, nocturnality is only one of four possible temporal niches, and understanding of the neural circadian system in diurnal, crepuscular, and cathemeral mammalian species is very much in its infancy. In this chapter, we review the fundamental properties of the neural circadian system in nocturnal rodents and then compare this with what is known about neural timekeeping in diurnal species. Through this, we identify gaps in our knowledge and key problems to investigate in order to gain a more complete understanding of circadian control of behaviour and physiology, particularly with regard to temporal niche preference.
Bano-Otalora, B., & Piggins, H. D. (2017). The mammalian neural circadian system: From molecules to behaviour. In Biological Timekeeping: Clocks, Rhythms and Behaviour (pp. 257–275). Springer (India) Private Ltd. https://doi.org/10.1007/978-81-322-3688-7_12