FINE MOTOR-PERFORMANCE IN SCHIZOPHRENIA

Peripheral and central aspects of motor dysfunction were assessed in 1 2 schizophrenic and 12 normal subjects, using a test of control of fin ger movement based on the widely used smooth pursuit eye movement task . This was performed in order to investigate the basis of neuromotor d ysfunction in schizophrenia. In this task, subjects used finger moveme nt to track a visual target. Simultaneously, an electromyogram of the extensor digitorum communis, the primary muscle utilized in the task, was recorded. Smooth pursuit eye movements were also assessed. Accurac y of finger-based and smooth-pursuit eye movement tracking was analyze d by fast Fourier transform and expressed as a log signal-to-noise rat io. The electromyograms were analyzed by motor unit potential discrimi nation and by interspike interval histography. Schizophrenics demonstr ated significantly poorer finger tracking than did controls, with a me an score of 2.01 +/- 0.63 (SD) versus 2.81 +/- 0.42 (t = 3.52, d.f. = 21, p < 0.005). However, there was no evidence for motor-unit dysfunct ion. Schizophrenics also performed more poorly on smooth-pursuit eye m ovement, with a mean score of 2.06 +/- 0.62 versus 3.33 +/- 1.21 (t = 3.21, d.f. = 22, p < 0.005). Severity of extrapyramidal symptoms was c orrelated with poorer performance on the finger tracking task, but not smooth-pursuit eye movement. These findings support the hypothesis th at schizophrenics' tracking abnormalities are due to central nervous s ystem deficits rather than peripheral pathology.