Quantitative characterization of eye tracking dysfunction in schizophrenia

The purpose of this study was to characterize the nature of the processes t hat are involved in eye tracking dysfunction (ETD). We identified a combina tion of quantitative measures that best distinguished qualitatively normal eye tracking from qualitatively abnormal eye tracking, using discriminant a nalysis. Discriminant scores distinguished schizophrenics with ETD from bot h schizophrenics with normal eye tracking and normal controls, but did not distinguish schizophrenics with normal eye tracking from normal controls, u nderscoring the heterogeneity of schizophrenic patients with respect to eye tracking. The results of the discriminant analysis indicated that ETD is a multivariate process involving a primary impairment in the smooth pursuit system characterized by increased catch-up saccades and reduced gain, and, secondarily, disinhibition of intrusive saccades, especially square-wave je rks. Quantitative characterization of ETD makes it possible to consider eye tracking as a quantitative trait in genetic investigations of a multidimen sional phenotype. (C) 2000 Elsevier Science B.V. All rights reserved.