Cerebral hemodynamics and capillary dysfunction in late-onset major depressive disorder

Area of Science:

• Neuroscience
• Vascular Biology
• Psychiatry

Background:

• Perfusion changes in major depressive disorder (MDD) are often attributed to altered neuronal activity.
• However, these changes may also reflect neurovascular coupling alterations due to impaired capillary function.

Purpose of the Study:

• To investigate capillary function in patients with late-onset MDD.
• To differentiate between neuronal activity changes and microvascular pathology in MDD.

Main Methods:

• Perfusion MRI was used to measure normalized cerebral blood flow (nCBF), cerebral blood volume (nCBV), and relative transit-time heterogeneity (RTH) in 22 MDD patients and 22 controls.
• Brain oxygenation, including oxygen tension and normalized metabolic rate of oxygen (nCMRO2), was estimated.

Main Results:

• MDD patients exhibited elevated RTH, indicating capillary dysfunction, in the anterior prefrontal cortex, ventral anterior cingulate cortex, and left insula.
• Hypometabolism (reduced nCBV, nCBF, nCMRO2) was observed in the subthalamic nucleus and globus pallidus, with preserved capillary function.
• Hyperactivity (increased nCBF) with preserved capillary function was noted in the cerebellum and brainstem.

Conclusions:

• Perfusion changes in MDD reflect both altered neuronal activity in deep nuclei and cerebellum, and microvascular pathology affecting neurovascular coupling in ventral circuits.
• Microvascular pathology may be a key factor in the etiology of late-onset MDD and subsequent brain activity changes.