Smooth pursuit eye movement differences between familial and non-familial schizophrenia

Disrupted smooth pursuit eye tracking characterizes a greater proportion of individuals with schizophrenia than in the normal population. The finding of a similar increased incidence of eye tracking abnormality in first degree relatives of schizophrenics implicates this disorder as a potential biological marker for schizophrenia. To test the assumption that the eye tracking dysfunction of schizophrenics is genetically related, left and right smooth pursuit gain and phase shift were compared between 20 schizophrenics with a family history of schizophrenia or schizophrenia-related disorders, 18 schizophrenics without a family history, as well as for 18 normal controls. Subjects tracked pendular targets on an LED light bar moving at frequencies of 0.2 and 0.7 Hz. Horizontal eye movements were recorded using DC-electro-oculography. Results indicate that schizophrenics with a positive family history had significantly reduced right pursuit gain compared with controls, while right gain for negative family history schizophrenics did not differ from either group. Schizophrenic subjects also were administered neuropsychological tests. Linear regression by groups analyses reveal that neuropsychological measures significantly predicted right gain to slower targets (0.2 Hz) for the positive family history schizophrenics, but not for negative family history schizophrenics.