Simultaneous stomach-brain electrophysiology reveals dynamic coupling in human sleep.

Sleep involves continuous communication between the brain and body, yet the dynamics of peripheral signals during human sleep remain poorly understood. Here we tested whether gastric electrophysiology exhibits infraslow structure and coordinated fluctuations with cortical rhythms indicative of sleep physiology. Simultaneous high-density electroencephalography (EEG) and electrogastrography (EGG) were recorded across sixty participants and three nights. Gastric power was consistently higher during NREM than REM sleep and declined across successive cycles, consistent with stage-dependent autonomic modulation of visceral activity. For the first time, we show that the gastric rhythm itself exhibits intrinsic infraslow amplitude modulations (∼0.007 Hz), which are selectively amplified during NREM sleep and temporally aligned with infraslow fluctuations in cortical sigma power, strongest during N3 sleep. Event-locked analyses further revealed transient increases in gastric amplitude following cortical slow wave oscillations, particularly when accompanied by sleep spindles. Across nights, variance in gastric infraslow amplitude predicted subjective sleep quality beyond standard polysomnographic and cardiac measures. Together, these findings position the human stomach as a peripheral oscillator whose infraslow dynamics track thalamocortical activity during sleep and predict subjective sleep quality, extending the interoceptive regulatory loop into the sleeping brain.