Brain Structural and Functional Alterations Specific to Low Sleep Efficiency in Major Depressive Disorder

Area of Science:

• Neuroscience
• Psychiatry
• Sleep Medicine

Background:

• Sleep disturbance is prevalent in major depressive disorder (MDD).
• Previous research on neural underpinnings of sleep issues in MDD is limited by subjective measures and single neuroimaging techniques.
• Objective sleep assessment and multi-modal neuroimaging are needed.

Purpose of the Study:

• To investigate the neural correlates of low sleep efficiency in patients with major depressive disorder (MDD) using multi-modal neuroimaging.
• To differentiate brain structure and function in MDD patients with normal versus low sleep efficiency.

Main Methods:

• Ninety-six MDD patients underwent polysomnography and multi-modal MRI scans.
• Patients were categorized into normal sleep efficiency (NSE) and low sleep efficiency (LSE) groups.
• Voxel-based morphometry (VBM), regional homogeneity (ReHo), functional connectivity strength (FCS), and tract-based spatial statistics (TBSS) were used to analyze structural, functional, and diffusion MRI data.

Main Results:

• No significant gray matter volume differences were observed between NSE and LSE groups.
• The LSE group exhibited increased axial diffusivity in specific white matter tracts (left superior/posterior corona radiata, left posterior internal capsule).
• The LSE group showed decreased ReHo in bilateral lingual gyri/right postcentral gyrus and increased FCS in the left angular gyrus.

Conclusions:

• Low sleep efficiency in MDD is characterized by preserved gray matter but impaired white matter integrity.
• Decreased local synchronization (ReHo) and increased functional connectivity strength (FCS) are specific to low sleep efficiency in MDD.
• These dissociations between structural and functional alterations offer insights into the neural mechanisms of sleep disturbance in depression.