AN INVESTIGATION INTO MOVEMENT PLANNING AND EXECUTION DEFICITS IN INDIVIDUALS WITH SCHIZOPHRENIA

The purpose of this study was to examine whether individuals with schi zophrenia demonstrate slowing in movement planning (reaction time), or in movement execution (movement time and velocity), in comparison to normals. Twelve schizophrenic and 12 control right-handed males perfor med aiming movements with a mouse (controlled by either the left or ri ght hand) on a graphics tablet towards targets of differing sizes and distances appearing on a computer screen. Results showed that, for rea ction time, the controls were faster than the schizophrenics and the l atter had a left hand advantage for movement preparation while the con trols showed no such differences. For movement time, no group differen ces were found. However, as expected, movement times were shorter (i.e ., movements were faster) to the large, and near targets. These result s support Fitts' law (Fitts, 1954) which describes a relationship wher e aiming movement time decreases as target distance decreases, and tar get size increases. We provide evidence here for a movement planning d eficit in schizophrenic patients with no decrement in movement executi on compared to controls.