Dorsolateral and dorsomedial prefrontal gray matter density changes associated with bipolar depression

Abstract

Mood states are associated with alterations in cerebral blood flow and metabolism, yet changes in cerebral structure are typically viewed in the context of enduring traits, genetic predispositions, or the outcome of chronic psychiatric illness. Magnetic resonance imaging (MRI) scans were obtained from two groups of patients with bipolar disorder. In one group, patients met criteria for a current major depressive episode whereas in the other no patient did. No patient in either group met criteria for a current manic, hypomanic, or mixed episode. Groups were matched with respect to age and illness severity. Analyses of gray matter density were performed with Statistical Parametric Mapping software (SPM5). Compared with non-depressed bipolar subjects, depressed bipolar subjects exhibited lower gray matter density in the right dorsolateral and bilateral dorsomedial prefrontal cortices and portions of the left parietal lobe. In addition, gray matter density was greater in the left temporal lobe and right posterior cingulate cortex/parahippocampal gyrus in depressed than in non-depressed subjects. Our findings highlight the importance of mood state in structural studies of the brain-an issue that has received insufficient attention to date. Moreover, our observed differences in gray matter density overlap metabolic areas of change and thus have implications for the conceptualization and treatment of affective disorders.

Fig. 1

Anterior surface rendering illustrating (in blue) areas in which depressed bipolar subjects showed lower gray matter density relative to euthymic bipolar subjects.

Fig. 2

A sequence of axial slices illustrating gray matter density differences in depressed bipolar subjects relative to euthymic bipolar subjects. Notable regions of lower gray matter density, shown in blue, are in the left temporal lobe and the right posterior cingulate and right parahippocampal gyrus. Regions of greater gray matter density, shown in red, are in the left dorsolateral prefrontal, right posterior cingulate, and parahippocampal gyrus, and bilateral occipital lobes. Talairach z-coordinates are provided to the upper left of each slice.