An evolving literature suggests a volume reduction and a loss of functional integrity of prefrontal cortex in depressed patients. Interhemispheric prefrontal functional integrity is mediated via the anterior portion of the corpus callosum. Until recently interhemispheric fibers connecting prefrontal cortex have not been well defined. In this study, we compared the corpus callosum area of depressed patients with controls using a novel schema proposed by Hofer and Frahm (2006) which defined a specific anterior callosal area for prefrontal interhemispheric fibers. We further investigated the correlation between callosal area and prefrontal cortical volume.
Thirty-six patients with major depressive disorder and thirty-three healthy controls were recruited. All subjects were psychotropic medication-free and right-handed. The imaging was performed on a 1.5T MR unit (Magnetom Vision Siemens). The images obtained from 3D MP-RAGE sequence were used for analyses. Medical Image Processing, Analyzing and Visualization (MIPAV) software was used for callosal and prefrontal measurements.
Depressed patients had reduced prefrontal cortical volume and a loss of the normal callosal/gray matter correlation, but normal white matter volume and normal callosal areas.
It is not known if the observed changes were preexisting or acquired.
Our results indicate that the normal structural relationship between anterior callosal area and prefrontal cortical volume is disrupted in major depressive disorder and that the disruption is due to reduced cortical volume rather than to changes in interhemispheric connections.