A model of smooth pursuit eye movement deficit associated with the schizophrenia phenotype

Smooth pursuit eye movement (SPEM) abnormalities in schizophrenia, although well described, are poorly understood. SPEMs are initiated by motion of an object image on the retina. During initiation, the eyes accelerate until they approximate target velocity and a state of minimal retinal motion is achieved. Pursuit is maintained through predictive eye movements based on extraretinal signals and corrections based on deviations from the fovea. Here, initiation and predictive pursuit responses were used to estimate the contributions of retinal and extraretinal signals to pursuit maintenance in schizophrenia patients' relatives. Relatives exhibited normal initiation, but had lower predictive pursuit gain compared with controls. Relatives had normal gain during pursuit maintenance, presumably by greater reliance on retinal error. This was confirmed by group differences in regression coefficients for retinal and extraretinal measures, and suggests that schizophrenia SPEM deficits involve reduced ability to maintain or integrate extraretinal signals, and that retinal error may be used to compensate.