Association of microstructural white matter abnormalities with cognitive dysfunction in geriatric patients with major depression

Major depression disorder (MDD) is one of the most common causes of disability in people over 60 years of age. Previous studies have linked affective and cognitive symptoms of MDD to white matter (WM) disruption in limbic-cortical circuits. However, the relationship between clinical cognitive deficits and loss of integrity in particular WM tracts is poorly understood. Fractional anisotropy (FA) as a measure of WM integrity was investigated in 17 elderly MDD subjects in comparison with 18 age-matched controls using tract-based spatial statistics (TBSS) and correlated with clinical and cognitive parameters. MDD patients revealed significantly reduced FA in the right posterior cingulate cluster (PCC) compared with controls. FA in the right PCC (but not in the left PCC) showed a significant positive correlation with performance in a verbal naming task, and showed a non-significant trend toward a correlation with verbal fluency and episodic memory performance. In control subjects, no correlations were found between cognitive tasks and FA values either in the right or left PCC. Results provide additional evidence supporting the neuronal disconnection hypothesis in MDD and suggest that cognitive deficits are related to the loss of integrity in WM tracts associated with the disorder.