Unravelling the neural circuitry for circadian regulation of sleep–wake cycles

Abstract

A requirement for the fruitful analysis of a neurobiological process is the identification of neural circuits that are crucial for effecting the process. Circadian rhythms constitute one ubiquitous, but mechanistically complex, process that is important for regulating a variety of behavioral states, including sleep and waking. The circadian rhythmicity of sleep–wake cycles might be regulated by trans-synaptic signalling between neurons located in hypothalamic nuclei and in the noradrenergic locus coeruleus (LC). LC neurons fire briskly during waking, and they are less active during slow-wave sleep. However, it is not known whether the LC system is importantly involved in the circadian regulation of arousal. Circadian regulation of the sleep–wake cycle probably involves the suprachiasmatic nucleus (SCN) of the hypothalamus; lesions of the SCN eliminate the circadian rhythmicity of the sleep–wake cycle. This observation, and others, led to the hypothesis that connections between the SCN and brain structures that modulate arousal might underlie the circadian regulation of sleep–wake cycles. Direct demonstration of functional projections from the SCN to brain centers that regulate arousal, such as the LC, is vital for revealing how the SCN and LC regulate arousal.A study by Aston-Jones et al 1xA neural circuit for circadian regulation of arousal. Aston-Jones, G. et al. Nat. Neurosci. 2001; 4: 732–738Crossref | PubMed | Scopus (352)See all