How do mice sleep? - briefly
Mice display polyphasic sleep, taking numerous short bouts spread across the 24‑hour cycle. They total about 12–14 hours of sleep, alternating between REM and non‑REM stages while often curled in a nest.
How do mice sleep? - in detail
Mice exhibit a polyphasic sleep pattern, dividing rest into multiple short bouts throughout the 24‑hour cycle. During daylight hours, when ambient light is low, they spend the majority of their time sleeping, accumulating roughly 12 to 14 hours of rest per day. Nighttime activity peaks, with brief interruptions for micro‑sleeps that last a few seconds to a couple of minutes.
Sleep architecture comprises alternating non‑rapid eye movement (NREM) and rapid eye movement (REM) phases. NREM periods dominate each bout, lasting 30 to 90 seconds, followed by REM episodes of 5 to 15 seconds. Electroencephalogram (EEG) recordings reveal characteristic low‑frequency, high‑amplitude waves during NREM and theta activity during REM, mirroring patterns observed in larger mammals.
Postural behavior reflects a preference for curled positions, with the body forming a tight ball and the tail wrapped around the torso. This configuration reduces exposed surface area, conserving heat. In a nest built from shredded bedding, mice further lower their metabolic rate, facilitating deeper sleep.
Environmental cues strongly influence the circadian rhythm. Light exposure suppresses melatonin production, prompting wakefulness, while darkness triggers the suprachiasmatic nucleus to initiate sleep onset. Temperature fluctuations affect sleep quality; optimal ambient temperatures (20‑26 °C) promote longer, uninterrupted bouts, whereas colder or hotter conditions increase fragmentation.
Nutritional status modifies sleep drive. Post‑prandial periods lead to brief elevations in wakefulness, while fasting can extend total sleep time as the organism conserves energy. Social factors also play a role; solitary mice tend to sleep longer than those housed in groups, where hierarchical dynamics introduce intermittent arousals.
Research methods include:
- EEG/EMG telemetry: implanted sensors record brain waves and muscle tone, distinguishing NREM from REM.
- Video tracking: infrared cameras monitor posture, movement, and nest use without disturbing the animal.
- Actigraphy: miniature accelerometers attached to the cage floor detect activity spikes corresponding to wake periods.
Collectively, these observations delineate a detailed portrait of murine sleep: frequent, short bouts dominated by NREM, tightly regulated by light, temperature, nutrition, and social environment, and characterized by a distinctive curled nesting posture.