Visuoaffective day residue in hypnagogia involves sequential bihemispheric interactions between cortical,...

Area of Science:

• Neuroscience
• Cognitive Science
• Sleep Research

Background:

• Waking experiences, or 'day residue', influence thought processes during sleep.
• The neural mechanisms underlying the processing of visual and emotional 'day residue' during hypnagogic sleep remain unclear.
• Understanding this interplay is crucial for deciphering how sleep consolidates waking mentation.

Purpose of the Study:

• To map the neural sources and functional connectivity associated with visuo-affective processing of 'day residue' during hypnagogic sleep.
• To investigate the relationship between electroencephalography (EEG) power, residue strength, and specific brain networks.
• To elucidate the dynamic interactions of brain structures involved in processing waking experiences during the transition to sleep.

Main Methods:

• Utilized a nap protocol with serial awakenings in 28 healthy participants.
• Included pre-sleep stimulation with affective visual images and assessment of semantic similarity between images and imagery reports.
• Employed 64-channel electroencephalography (EEG) for source estimation and functional connectivity analysis, alongside affect ratings.

Main Results:

• Low-frequency EEG power correlated with weaker 'day residue', while high-frequency EEG power correlated with stronger residues.
• Distinct neural source networks were associated with imagetic and affective residues across wake-sleep states.
• Significant overlap was found with the default mode network during N1 sleep (50% for imagetic, 61% for affective residues).

Conclusions:

• Identified neural correlates for the visuo-affective processing of 'day residue' during hypnagogic sleep.
• Demonstrated that hypnagogic processing involves complex, dynamic, and sequential bi-hemispheric interactions across multiple brain structures.
• Highlighted the involvement of visual, limbic, optokinetic, and cognitive networks in integrating waking experiences during sleep onset.