To sleep or not to sleep: neuronal and ecological insights

Abstract

Daily, animals need to decide when to stop engaging in cognitive processes and behavioral responses to the environment, and go to sleep. The main processes regulating the daily organization of sleep and wakefulness are circadian rhythms and homeostatic sleep pressure. In addition, motivational processes such as food seeking and predator evasion can modulate sleep/wake behaviors. Here, we discuss the principal processes regulating the propensity to stay awake or go to sleep-focusing on neuronal and behavioral aspects. We first introduce the neuronal populations involved in sleep/wake regulation. Next, we describe the circadian and homeostatic drives for sleep. Then, we highlight studies demonstrating various effects of motivational processes on sleep/wake behaviors, and discuss possible neuronal mechanisms underlying their control.

Figure 1

A schematic of the main factors controlling sleep/wake states. Multiple internal and external signals can modulate the propensity of animals to stay awake or to go to sleep. Distributed networks in the brain integrate these often-conflicting variables to generate a coherent output that results in consolidated sleep.