Perivascular space diffusivity and brain microstructural measures are associated with circadian time and sleep...

Area of Science:

• Neuroscience
• Human neuroimaging

Background:

• The glymphatic system facilitates brain waste clearance, enhanced during sleep.
• Synaptic homeostasis hypothesis suggests sleep downscales synapses, impacting brain microstructure.
• Previous research primarily focused on animal models, necessitating human studies.

Purpose of the Study:

• To investigate the relationship between brain diffusivity, microstructure, and time of day, sleep quality, and cognitive performance in humans.
• To explore how circadian time influences brain imaging metrics.
• To determine the impact of sleep quality on brain structure and cognitive function.

Main Methods:

• Utilized diffusion-weighted images from 916 healthy young adults (22-37 years) from the Human Connectome Project.
• Assessed diffusion tensor image analysis along the perivascular space (DTI-PAV) index, white matter fractional anisotropy (FA), intra-neurite volume fraction (IVF), and extra-neurite mean diffusivity (MD).
• Correlated imaging metrics with circadian time, Pittsburgh Sleep Quality Index (PSQI), and cognitive function scores.

Main Results:

• DTI-PAV index and orbitofrontal grey matter MD negatively correlated with circadian time; white matter FA positively correlated.
• Grey matter IVF positively correlated with PSQI, driven by sleep duration.
• Grey matter IVF positively correlated with cognitive function, with negative interactions between cognitive function and PSQI.

Conclusions:

• Perivascular cerebrospinal fluid flow appears to be under circadian control in humans.
• Sleep downregulates grey matter intra-neurite volume in healthy adults, positively impacting cognitive function.
• Findings link glymphatic system function, sleep, and cognitive performance in humans.