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L. Elliot Hong, MD; Braxton D. Mitchell, PhD; Matthew T. Avila, PhD; Helene Adami, MSW; Robert P. McMahon, PhD; Gunvant K. Thaker, MD

Arch Gen Psychiatry. 2006;63:259-264.

Background  Abnormal smooth pursuit eye movements (SPEMs) are some of the most reproducible biological changes associated with the susceptibility for schizophrenia. Recent studies have suggested that deficit in predictive pursuit, a specific component of the SPEMs, marks schizophrenia susceptibility.

Objective  To test whether predictive pursuit contains less extraneous noise and may be under more direct genetic control than the traditional measure of overall pursuit performance using maintenance pursuit gain.

Design  Familial aggregation estimation of the predictive pursuit measure and the traditional maintenance pursuit measure in sibling pairs from families of schizophrenic patients.

Setting  Outpatient clinics.

Participants  Patients with schizophrenia and their full siblings were recruited, provided that at least 1 sibling pair could be formed per family. Ninety-two siblings were recruited into the study. They formed 70 sibling pairs. Ninety healthy control subjects were also recruited using targeted local community advertisements based on patients' county of residence, aiming to capture the basic demographics of the regions from which the patients were recruited.

Main Outcome Measures  Familial correlations and heritability estimates of 2 SPEM measures: maintenance pursuit gain and predictive pursuit gain.

Results  The sibling intraclass correlation coefficient of the predictive pursuit gain (r = 0.45-0.48) was significantly higher than that of maintenance pursuit gain (r = 0.02-0.20) (P = .005-.007). Variance component analysis suggested a high genetic loading for predictive pursuit (heritability = 0.90, SE = 0.22; P<.001) but relatively low heritability in the traditional maintenance pursuit measure (heritability = 0.27, SE = 0.21; P = .08).

Conclusion  These results suggest that predictive pursuit may index stronger genetic effect and may be better suited for genetic studies than the traditional SPEM measure of maintenance pursuit gain.

Author Affiliations: Maryland Psychiatric Research Center, Department of Psychiatry (Drs Hong, Avila, McMahon, and Thaker and Ms Adami), and Department of Medicine (Dr Mitchell), University of Maryland School of Medicine, Baltimore.

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