Altered thalamocortical and intra-thalamic functional connectivity during light sleep compared with wake

Area of Science:

• Neuroscience
• Sleep Science
• Functional Neuroimaging

Background:

• The transition from wakefulness to sleep involves altered brain activity, particularly in the thalamocortical network.
• Previous studies reported decreased thalamocortical functional connectivity (FC) during sleep, but pathway-specific differences and intra-thalamic patterns remain unclear.

Purpose of the Study:

• To investigate thalamocortical and intra-thalamic FC changes across sleep stages non-invasively.
• To determine how sleep differentially affects FC in distinct thalamic subdivisions and their cortical projections.

Main Methods:

• Simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) were recorded in 13 healthy participants transitioning into light sleep.
• EEG data was visually scored for sleep staging.
• Seed-based FC analysis was used to derive a functional thalamic parcellation during wakefulness.

Main Results:

• Sleep differentially impacted FC between thalamic subdivisions and cortical regions.
• Significant increases in FC during sleep were observed specifically in sensorimotor connections.
• Intra-thalamic FC, both within and between subdivisions, significantly increased with advancing sleep.

Conclusions:

• Thalamocortical and intra-thalamic relationships are complex and state-dependent across the sleep-wake cycle.
• The findings underscore the significance of the thalamocortical network in understanding sleep mechanisms.
• Sleep alters brain connectivity in specific, non-uniform ways across different brain networks.