Do mice sleep, and when? - briefly
Yes, mice sleep, averaging 12–14 hours daily, primarily during the light phase of the day. Their rest occurs in multiple short bouts rather than a single uninterrupted period.
Do mice sleep, and when? - in detail
Mice are nocturnal mammals that allocate a substantial portion of each 24‑hour cycle to sleep. Adult laboratory mice typically spend 12–14 hours sleeping per day, divided into multiple short bouts rather than a single extended period. Their sleep architecture comprises rapid eye movement (REM) and non‑REM (NREM) stages, each lasting only a few minutes before transitioning.
Key characteristics of mouse sleep:
- Polyphasic pattern – several episodes of sleep occur throughout both the dark (active) and light (rest) phases.
- NREM dominance – about 80 % of total sleep time is spent in NREM, characterized by slow-wave activity and reduced muscle tone.
- Brief REM episodes – REM periods represent roughly 20 % of sleep, lasting 1–2 minutes and occurring mainly toward the end of each sleep bout.
- Circadian influence – the light‑dark cycle strongly modulates sleep timing; during the light phase, mice show longer and more consolidated sleep, while the dark phase contains shorter, fragmented episodes interspersed with activity.
Physiological markers confirm these patterns. Electroencephalogram (EEG) recordings reveal high-amplitude delta waves during NREM and low-amplitude, mixed-frequency activity during REM. Electromyogram (EMG) signals show muscle atonia in REM and reduced tone in NREM.
Environmental factors such as cage enrichment, temperature, and stress can shift the proportion of sleep stages and alter total sleep duration. For instance, elevated ambient temperature shortens REM bouts, whereas enriched environments may increase overall sleep time by reducing anxiety-driven arousal.
In summary, mice exhibit a highly fragmented, polyphasic sleep schedule with a predominance of NREM sleep, regulated by circadian cues and sensitive to external conditions. This detailed understanding supports the use of mice as models for investigating sleep physiology and related disorders.