An investigation into movement planning and execution deficits in individuals with schizophrenia.

The purpose of this study was to examine whether individuals with schizophrenia 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 performed aiming movements with a mouse (controlled by either the left or right hand) on a graphics tablet towards targets of differing sizes and distances appearing on a computer screen. Results showed that, for reaction time, the controls were faster than the schizophrenics and the latter had a left hand advantage for movement preparation while the controls showed no such differences. For movement time, no group differences were found. However, as expected, movement times were shorter (i.e., movements were faster) to the large, and near targets. These results support Fitts' law (Fitts, 1954) which describes a relationship where aiming movement time decreases as target distance decreases, and target size increases. We provide evidence here for a movement planning deficit in schizophrenic patients with no decrement in movement execution compared to controls.