Smooth pursuit eye tracking dysfunction in schizophrenia: subcortical implications.

The study of smooth pursuit eye tracking behavior in schizophrenics has occupied a prominent position in the search for biological correlates of this mental illness for nearly 20 years. During this time, impairments in this behavior have been shown to be a most robust finding in these patients. Attempts to further characterize the basis for this dysfunction have emphasized the role of cortical--particularly frontal--processes in both the symptomatology of schizophrenia and the eye tracking disturbance. In the present paper, arguments are made in support of a subcortical contribution to smooth pursuit eye tracking dysfunction in schizophrenia. Supporting data include new observations of cortical EEG variations in association with pursuit tracking disruptions, and a review of recent data indicating visual-vestibular and cerebellar-vestibular influences on the tracking disturbances in these patients. On the basis of such data, it is concluded that it is highly unlikely that a single mechanism or process is exclusively responsible for impaired pursuit tracking in schizophrenics, and that there are data to support both cortical and subcortical contributions to this dysfunction.