Abstract
Maintenance of motor set in patients with unipolar major depression was examined. Twelve melancholic and 12 non-melancholic depressed patients and 24 age matched controls performed a serial choice reaction time task while external cues aiding maintenance of a motor set were systematically removed. Melancholic patients were significantly slower than controls with no reduction in external cues and with a moderate reduction in external cues. At a high level of reduction in external cues, seven of 12 melancholic patients (but only three of 12 non-melancholic patients and controls) were unable to complete the task; suggesting a greater reliance on external cues, perhaps implicating a failure of motor planning ability in melancholic patients. This, in turn, may point to a prefrontal (premotor) deficit in melancholic depression, with possible commonalities with Parkinson's disease.