Procedural learning in schizophrenia: evidence from serial reaction time.

Although schizophrenic patients, as a group, show deficits on measures of explicit learning, it is unclear whether they also have deficits on measures of implicit learning. The current study assessed procedural learning in a sample of 48 chronic schizophrenic inpatients and 23 normal controls using the serial reaction time test (SRT). In addition, we examined the clinical correlates of procedural learning. The SRT yields indices of total motor learning and two subcomponents: reaction time learning, and sequence learning. Although patients performed comparably to normal controls on total motor learning, they showed significantly less sequence learning (P <.03) than controls. Reaction time learning did not differ between the two groups. None of the symptom or clinical variables was correlated with the indices of learning. Chronic schizophrenic inpatients showed normal levels of procedural learning on the SRT. However, their learning was qualitatively different than that of controls (i.e. patients showed deficits in sequence learning, but not reaction time learning). Reduced sequence learning could reflect dysfunctional cortico-cerebellar circuits.