Objective: Disordered smooth-pursuit eye movements (SPEM) and, specifically, small anticipatory saccades that disrupt SPEM have been hypothesized to be a marker of genetic vulnerability to schizophrenia. This study compares SPEM in children of schizophrenic parents with normally developing control children to assess whether SPEM abnormalities are also present in a subset of at-risk children.
Method: With infrared oculography, SPEM was examined in 13 children of schizophrenic parents and 19 normally developing controls (aged 6 to 15 years). Measures of smooth-pursuit gain and root mean square error were used in addition to more specific measures of catch-up saccades and anticipatory saccades.
Results: Children of schizophrenic parents differed from normally developing controls on gain and root mean square error, but not on catch-up saccades. Small anticipatory saccades were significantly more frequent in the at-risk group. The percentage of total eye movements due to anticipatory saccades identified 54% of the at-risk group (compared with none of the control group) as performing more than two standard deviations above (worse than) the control mean.
Conclusions: The presence of increased anticipatory saccades is evidence for an oculomotor dysfunction that may be a phenotype of the genetic risk for schizophrenia, expressed years prior to the possible development of clinical illness.