Tracing diurnal differences in brain anatomy with voxel-based morphometry - associations with sleep characteristics

Area of Science:

• Neuroscience
• Chronobiology
• Neuroimaging

Background:

• Circadian rhythms influence brain functions like arousal, motivation, and cognition.
• Magnetic resonance imaging (MRI) allows macroscopic study of diurnal brain processes, but neuroanatomical research is limited.

Purpose of the Study:

• To investigate the impact of time-of-day (TOD) on white matter (WM) and grey matter (GM) volumes.
• To assess the replicability of observed diurnal effects on brain volumes.
• To correlate the magnitude of diurnal brain volume changes with sleep health indices.

Main Methods:

• Voxel-based morphometry (VBM) was used to analyze brain volumes in a dataset of 72 participants.
• The dataset was divided into two comparable subsamples to ensure replicability.
• Actigraphy data was used to derive indices of sleep health.

Main Results:

• TOD was primarily associated with regional decreases in WM volume.
• Volumetric decreases in GM were corroborated, with novel evidence for TOD-related volumetric increases.
• Replicability was higher for WM effects. Replicated GM findings included volumetric increases in the amygdala and hippocampus, and decreases in the retrosplenial cortex, which were more pronounced in individuals with shorter sleep durations.

Conclusions:

• Diurnal variations influence both white and grey matter volumes in the brain.
• Region-specific mechanisms underlie grey matter changes, potentially linked to wakefulness and sleep homeostasis.
• Sleep duration moderates some diurnal grey matter effects, highlighting the interplay between sleep and brain structure.