Lying posture affects sleep structures and cortical activities: a simultaneous EEG-fMRI imaging of the sleeping and waking brain

Lying posture influences both neural activity and cognitive performance, and it is essential to sleep hygiene. Whereas, no neuroimaging research has investigated the effect of lying position on brain activity in waking and sleeping conditions. Therefore, we recruited 35 participants to perform a within-participant simultaneous EEG-fMRI recording with lying supine and lateral postures. Our results showed that sleep onset latency (SOL) was affected by both sleep position preference (SPP) and lying poses. SOL in supine was significantly shorter than that in lateral posture. The correlation analysis between SPP and sleep parameters indicated that individuals who prefer supine had less SOL and N2 sleep durations. However, we did not find this significant correlation in lateral-prefer individuals. Besides, different sleep positions mainly caused an alteration of the differences in brain activity patterns. In supine posture, the brain activities in the left precuneus, and anterior cingulate cortex were greater than those in lateral position. However, in the lateral posture, the status was just the opposite. Finally, we also found that the right putamen was sensitive to habitual sleep posture in the awake state. The participants who prefer to lie supine tend to have higher activity in the putamen. Our study may help with the understanding of the contribution of lying posture on brain activity and its relationship with posture preference in sleep.