Mental rotation in unipolar major depression.

Mental rotation (MR) performance may be used as an index of mental slowing or bradyphrenia, and may reflect, in particular, speed of motor preparation. MR was employed with a sample of both melancholic (n=8) and non-melancholic (n=9) unipolar depressed patients and healthy controls (n=10) to determine if motor slowing associated with depression might be reflected in slowed motor preparation (as reflected in slope of the MR function) independent of actual motor slowing (overall response time). Both melancholic and non-melancholic patients showed a generalised slowing relative to controls, perhaps reflecting bradykinesia and akinesia. This effect was significantly greater in the melancholic group than in the non-melancholic group. Relative to both the controls and the non-melancholic groups, the melancholic patients showed a progressive slowing with increasing angle of orientation indicating a specific slowing of MR. This deficit suggests a role of slowed motor planning in the psychomotor retardation of patients with melancholic depression.