DYNAMICAL ASPECTS OF MOTOR AND PERCEPTUAL PROCESSES IN SCHIZOPHRENIC-PATIENTS AND HEALTHY CONTROLS

The present study examined the temporal stationarity of the performanc e of 16 schizophrenic patients and 16 controls matched for age and sex in a bimanual coordination task and a perceptual task. In the motor t ask, rhythmic finger oscillations (alternating activity of homologue m uscle groups) at increasing speed levels resulted in two measures, the preferred oscillation frequency and the critical frequency at which p hase transitions (change towards simultaneous activity of homologue mu scle groups) occurred. A measure of local dimensional complexity (poin twise D2 or PD2), which is a measure of non-linear dynamics, was deter mined for the acceleration profiles of the subjects' movements. Schizo phrenics exhibited less stable movement dynamics than controls in hori zontal finger cycling, indicated by a lower ratio critical/preferred f requency (critical ratio) and by higher means and standard deviations of the pointwise D2. In vertical cycling, the critical ratio did not d ifferentiate between groups, while PD2 means and standard deviations d id. Groups also differed specifically in perception of two ambiguous f igures (Schroeder stairs and Rubin vase). Schizophrenics showed signif icantly higher reversal rates for the Rubin vase and a differential pe rceptive in comparison to controls in the perception of the Schroeder stairs. Measures of perceptual and motor stability were unrelated, whi ch suggests that perceptual and motor processes are not influenced by a common underlying mechanism. (C) 1998 Elsevier Science B.V. All righ ts reserved.