Motor control of schizophrenics--I. Oculomotor control of schizophrenics: a deficit in sensory processing, not strictly in motor control.

An in-depth analysis of eye movements of schizophrenics has demonstrated defects in several oculomotor subsystems, likely due to processing of sensory information and not to problems in the motor system itself. Schizophrenic subjects made more pursuit tracking errors, due to higher RMS errors, larger phase lag, and more saccades in pursuit. When making saccadic movements they had normal reaction times, saccade velocity and intersaccadic pause, but made more double-jump saccades and overshot the target. Only some had inability to hold steady fixation, but all had an attentional problem in restraining an inappropriate eye movement. The multiple defects suggest a processing problem that is not strictly motor and does not fit any standard definition of attention.