Chronotype differences in cortical thickness: grey matter reflects when you go to bed

Area of Science:

• Neuroscience
• Chronobiology
• Brain Imaging

Background:

• Humans exhibit distinct chronotypes (early, intermediate, late) based on circadian rhythms.
• Neural substrates underlying chronotype variations are not well understood.

Purpose of the Study:

• To investigate structural differences in the cerebral cortex across early (EC), intermediate (IC), and late (LC) chronotypes.
• To explore the relationship between chronotype and cortical volume, thickness, and folding patterns.

Main Methods:

• Utilized 3 Tesla MRI scans on 16 ECs, 16 ICs, and 16 LCs.
• Applied voxel-based morphometry (VBM) and vertex-wise cortical thickness (CTh) analysis to assess grey matter differences.

Main Results:

• Early chronotypes (ECs) showed reduced grey matter volume in the lateral occipital cortex and precuneus compared to LCs.
• ECs also exhibited lower grey matter in the lingual gyrus, occipital fusiform gyrus, and occipital pole compared to ICs.
• Cortical thickness analysis revealed lower grey matter in ECs within the left anterior insula, precuneus, inferior parietal cortex, and right pars triangularis compared to LCs.

Conclusions:

• Chronotype is associated with specific neural substrates, including variations in cortical thickness, surface area, and folding.
• These structural differences may underlie observed variations in behavior and brain function related to chronotype.
• Chronotype should be considered a potential modulating factor in structural brain imaging studies.