Bright light shapes diurnal sleep–wake rhythms with associated cFos activity in the anterior paraventricular thalamus in the Nile grass rat

Understanding how environmental light shapes sleep-wake regulation in diurnal mammals is essential for developing experimental models relevant to human physiology and sleep disorders. This study provides a comprehensive EEG/EMG-based characterization of sleep architecture in the Nile grass rat, a diurnal rodent with strong potential as a model for seasonal affective disorders. Bright daytime light enhanced arousal, reduced NREM and REM sleep, and increased delta power, revealing intensity-dependent modulation of sleep quantity and quality. cFos mapping further identified the anterior paraventricular thalamus as a candidate node linking light exposure to arousal regulation. These findings position the Nile grass rat as a valuable experimental species for investigating the mechanisms underlying human circadian sleep-wake organization and its modulation by environmental light.