A Naturalistic Paradigm to Probe Conscious Information Processing During Sleep

Sleep was long considered a passive mental state. The extent to which external information is integrated in, and consciously processed during sleep remains unknown. Here, simultaneous electroencephalographic (EEG) and functional magnetic resonance imaging (fMRI) data were collected from sleeping participants. First, the stimulus elicited significantly correlated fMRI activity in the auditory and fronto-parietal networks of awake participants. Behavioural testing found individuals to perceive the story’s suspense similarly. Then neural activity related to high-level processing of the story was investigated in 5 individuals who slept through it. Fronto-parietal activity in 1 individual in rapid eye movement (REM) sleep followed that of the wakeful individuals and was also predicted by the suspense ratings. This activity was not observed in non-REM individuals. REM is a known substrate for vibrant dreams, but these results suggest that it may also allow for high-level processing of exogenous auditory information