Frequency-dependent connectivity in large-scale resting-state brain networks during sleep

Area of Science:

• Neuroscience
• Sleep Science
• Brain Connectivity

Background:

• Functional connectivity (FC) patterns change across sleep stages.
• The precise spatial and temporal dynamics of these FC fluctuations, especially frequency-dependent changes, are not fully understood.

Purpose of the Study:

• To investigate frequency-dependent, network-level FC fluctuations during nocturnal sleep in healthy young adults.
• To examine how FC within and between resting-state networks changes across NREM2, NREM3, and REM sleep stages.

Main Methods:

• Utilized high-density electroencephalography (hdEEG) in 29 healthy young adults.
• Analyzed source-localized FC in resting-state networks during the first three sleep cycles.
• Sleep stages (NREM2, NREM3, REM) were scored using a semi-automatic procedure.

Main Results:

• FC within and between resting-state networks decreased from NREM2 to NREM3 sleep across multiple frequency bands and sleep cycles.
• During REM sleep, delta and sigma bands showed persistent connectivity breakdown, while alpha and beta bands exhibited reconnection in specific networks.
• Gamma-band FC increased in most network pairs during later REM sleep cycles.

Conclusions:

• The study elucidates the spatial and temporal characteristics of connectivity breakdown during deepening NREM sleep.
• Complex, frequency- and network-specific breakdown and reconnection processes characterize FC during REM sleep.