# Integrating Astrocytes in the Sleep–Wake Cycle: The Time Is Now

## TL;DR

Astrocytes play a key role in regulating sleep and circadian rhythms, acting as integrators of internal and environmental signals in the brain.

## Contribution

The paper introduces astrocytes as integrators of sleep homeostasis and circadian timekeeping, challenging neuron-centric models.

## Key findings

- Astrocytic calcium dynamics correlate with sleep states and can alter sleep architecture when manipulated.
- Astrocytes autonomously drive circadian timekeeping through rhythmic GABA and glutamate pulses.
- Astrocytes may reconcile contradictory findings by integrating internal states and environmental cues into neuronal circuits.

## Abstract

Astrocytes are emerging as critical regulators of the sleep–wake cycle, actively contributing to both sleep homeostasis and circadian rheostasis. This dual role challenges neuron‐centric frameworks that have dominated sleep and circadian biology and highlights astrocytes as potential integrators of internal temporal information. Experimental evidence shows that astrocytic calcium dynamics correlate with sleep state and that manipulating astrocytes can alter sleep architecture and homeostasis. In parallel, key aspects of circadian timekeeping can be autonomously driven by astrocytic clocks, with pulses of rhythmic GABA and glutamate able to synchronize circadian circuits and support circadian patterns of behavior. These findings are coherent with the idea that astrocytes can act as context‐dependent integrators to convey environmental cues and internal states to neuronal circuitries and promote adaptive behavior. Incorporating astrocytes into conceptual models of the sleep–wake cycle may help reconcile contradictory findings and offer new frameworks to better understand how salient internal temporal representations are encoded within the brain.

Astrocytes actively regulate sleep homeostatic and circadian rheostatic processes, underpinning the sleep–wake cycle. By acting as context‐dependent integrators of internal state and rhythmic environmental inputs, they modulate the encoding properties of neuronal circuitries and contribute to salient temporal representations in the brain.