Longitudinal brain volume changes in major depressive disorder.

Patients with major depressive disorder (MDD) exhibit gray matter volume (GMV) reductions in limbic regions. Clinical variables-such as the number of depressive episodes-seem to affect volume alterations. It is unclear whether the observed cross-sectional GMV abnormalities in MDD change over time, and whether there is a longitudinal relationship between GMV changes and the course of disorder. We investigated T1 structural MRI images of 54 healthy control (HC) and 37 MDD patients in a 3-Tesla-MRI with a follow-up interval of 3 years. The Cat12 toolbox was used to analyze longitudinal data (p < 0.05, FWE-corrected, whole-brain analysis; flexible factorial design). Interaction effects indicated increasing GMV in MDD in the bilateral amygdala, and decreasing GMV in the right thalamus between T1 and T2. Further analyses comparing patients with a mild course of disorder (MCD; 0-1 depressive episode during the follow-up) to patients with a severe course of disorder (SCD; > 1 depressive episode during the follow-up) revealed increasing amygdalar volume in MCD. Our study confirms structural alterations in limbic regions in MDD patients and an association between these impairments and the course of disorder. Thus, we assume that the reported volumetric alterations in the left amygdala (i.e. volumetric normalization) are reversible and apparently driven by the clinical phenotype. Hence, these results support the assumption that the severity and progression of disease influences amygdalar GMV changes in MDD or vice versa.

Effects of Long-Term Mindfulness Meditation on Brain's White Matter Microstructure and its Aging.

Although research on the effects of mindfulness meditation (MM) is increasing, still very little has been done to address its influence on the white matter (WM) of the brain. We hypothesized that the practice of MM might affect the WM microstructure adjacent to five brain regions of interest associated with mindfulness. Diffusion tensor imaging was employed on samples of meditators and non-meditators (n = 64) in order to investigate the effects of MM on group difference and aging. Tract-Based Spatial Statistics was used to estimate the fractional anisotrophy of the WM connected to the thalamus, insula, amygdala, hippocampus, and anterior cingulate cortex. The subsequent generalized linear model analysis revealed group differences and a group-by-age interaction in all five selected regions. These data provide preliminary indications that the practice of MM might result in WM connectivity change and might provide evidence on its ability to help diminish age-related WM degeneration in key regions which participate in processes of mindfulness.