Voluntary movement dysfunction in schizophrenics.

Several aspects of fine motor control were compared in schizophrenics and two control populations. The motor behavior analyzed was a button-press response in a forced choice paradigm. Three areas of abnormality were seen in schizophrenics: first, the interval preceding the motor response was characterized by reduced motor steadiness prior to the button-press response; second, the motor response was made with excessive force (hyperdynamia); and third, the agonist-antagonist synchrony (motor reversal) was impaired. Schizophrenics on and off neuroleptics did not differ on any measure of motor control, but schizophrenics with clinically observed tardive dyskinesia were found to have significantly less steadiness prior to the motor response than other schizophrenics.