Vertex-based morphometry in euthymic bipolar disorder implicates striatal regions involved in psychomotor function.

We hypothesized that psychomotor disturbances in patients with bipolar disorder are associated with morphometric changes in functionally specific regions of the basal ganglia and thalamus. We used structural magnetic resonance imaging and vertex-based morphometry to investigate whether psychomotor performance is associated with changes in volume and shape in euthymic subjects with bipolar disorder (n=27) compared with matched healthy controls (n=27). We saw no significant differences between age- and sex-matched groups in motor performance. We found a statistically significant group difference in the shape of the right putamen in the absence of psychomotor disturbances. There was an association between shape and motor performance in controls that was lacking in patients. We conclude that euthymic subjects with bipolar disorder without psychomotor disturbances show shape changes in regions of the right putamen that contribute to executive functions and motor function. It may be that other brain regions sustain the psychomotor functions that produce nearly identical motor performance in both groups.