Functional connectivity dynamics slow with descent from wakefulness to sleep

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Sleep Science

Background:

• The transition from wakefulness to sleep involves significant alterations in brain function.
• Understanding changes in interregional functional connectivity during this transition is crucial for comprehending brain dynamics.

Purpose of the Study:

• To investigate the implications of the wakefulness-sleep transition on interregional functional connectivity.
• To analyze the dynamic changes in functional connectivity over time during the transition from wakefulness to sleep.

Main Methods:

• Simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) were employed in 21 healthy participants.
• fMRI data were decomposed using independent component analysis (ICA) to identify neurophysiological sources.
• Static and dynamic functional connectivity (FC) were estimated using independent component time courses, a sliding window approach, and k-means clustering.

Main Results:

• Static functional connectivity (FC) between brain regions was largely similar during wakefulness and Stage-2 Sleep (NREM2).
• Dynamic FC exhibited significant differences between wakefulness and NREM2 sleep.
• Transitions between different FC states occurred more frequently during wakefulness compared to NREM2 sleep.

Conclusions:

• The dynamics of brain functional connectivity change substantially during the transition from wakefulness to sleep.
• Slower FC dynamics during sleep may be related to reduced effective connectivity and synaptic strength.
• These findings provide insights into the neural mechanisms underlying sleep and its impact on brain network organization.