Smooth pursuit tracking deficits of patients with schizophrenia at specific within-sine wave bins

Early information processing deficits are consistently reported for patients with schizophrenia on smooth pursuit tracking tasks. A growing number of studies have applied a transient (magnocellular) or sustained (parvocellular) explanation to account for deficient processing of briefly presented visual stimuli, moving stimuli, and particularly, stimuli requiring smooth tracking eye movements in patients with schizophrenia.

Although the preponderance of findings offer support for transient (where is it?) as opposed to sustained (what is it?) deficit, a need remains for specific depiction of the deficit. This was accomplished by applying a unique analytic method to a smooth pursuit tracking task.

Fourteen patients with schizophrenia and fifteen normal control subjects were tested on smooth pursuit tracking performance at five different "within-wave" dot velocity frequencies that ranged from .3 to 1.1 hz. Performance data was extracted from each of the five frequencies and then separated into 12 discrete components that corresponded to light velocity (i.e., 12 bins).

A repeated measures multivariate analysis of covariance indicated that the performance of patients with schizophrenia was significantly poorer than that of their normal counterparts for three separate analyses of the time in smooth pursuit, F(11,594) = 8.99; p <0.00001, percentage of time in smooth pursuit, F(11,594) = 3.06; p <0.0005, and time in saccade eye movement, F(11,594) = 3.11; p <0.0004. A regression analysis revealed that the medication dosage was not significantly associated with performance on any of the critical measures, although trends were observed.

The findings provide support for an early information processing deficit in patients with schizophrenia. In addition, the results support the current neurophysiologic model for abnormal smooth pursuit tracking in patients with schizophrenia, specifically implicating a transient channel deficiency.