Differences in Voxel-based Morphometry of Different Brain Structures in Patients With Mood Disorder Bipolar Mania in Comparison to Morphometry of Nrmal Controls

It is recognized that lesions in some specific neuro-anatomic areas due to brain disease, e.g., stroke or brain tumor, may lead to the development of secondary depression. The possibility of structural brain abnormalities as a cause of depression stimulated the use of structural brain imaging studies. Developments in structural neuroimaging by computed tomography and magnetic resonance imaging in the past 15 years facilitated the direct examination of specific brain structures, making the study of the relationship between anatomy and psychopathology is possible.

Neuro-anatomic model of mood regulation :

The prefrontal cortex has extensive connectivity to cortical and subcortical circuits that may underlie its importance in cognitive functions and modulation of limbic activity .The main subcortical structures participating in these circuits are the basal ganglia, thalamus, hypothalamus, brainstem, and the white matter tracts that connect these structures among themselves and to the cerebral cortex . A limbic-thalamic-cortical circuit consisting of the amygdala, the medio-dorsal nucleus of the thalamus, and the medial and ventro-lateral prefrontal cortex, and a limbic-striato-pallidal-thalamic circuit comprising the striatum, the ventral pallidum, and the components of the other circuit are the main neuro-anatomic circuits that have been proposed to participate in the pathophysiology of mood disorders.

The basal ganglia connect with cortical and limbic regions through circuits that, despite functioning segregated, are organized in parallel , in such a way that lesions in different parts of these circuits could result in malfunction. Additionally, the cerebellum, through connections with the brainstem and limbic structures, may also be involved in mood regulation.

Both primary and secondary mood disorders may involve abnormalities in specific fronto-subcortical neuro-anatomic circuits. Abnormalities in these brain regions or in contiguous areas that can affect the connections between these regions could reflect malfunction of these circuits, associated with development of mood disorders. Alternatively, abnormalities in these circuits could confer vulnerability to mood disorders, and its onset could be determined by interactions with environmental and genetic factors. Deficits during brain development due to these factors could result in under-development of particular brain areas, which could be related subsequently with mood disorders. The aging process or pathology such as vascular brain disease could result in atrophy of some of these regions. Thus, the influence of genetic, environmental, developmental, and degenerative factors during the development of these brain structures may determine the onset of mood disorders .