The effects of age on a smooth pursuit tracking task in adults with schizophrenia and normal subjects

Background: Performance during a smooth pursuit eye movement (SPEM) task has been proposed as a marker of genetic risk for schizophrenia, although the precise component of SPEM tracking most associated with genetic risk remains undetermined. Normal adult aging is associated with deterioration on SPEM tasks; it remains unclear whether investigations of SPEM abnormalities will allow inclusion of older subjects in genetic studies. This study examines 1) the effect of normal aging on several components of SPEM performance; and 2) whether schizophrenic–normal differences found in young adults continue over a broad adult age span. Methods: SPEM was recorded during a 16.7° per sec constant velocity task in 64 normal adults, ages 18 to 79 years, and 58 schizophrenic subjects, ages 18 to 70 years. Results: Smooth pursuit gain, the percent of total eye movements due to catch-up saccades, the frequency of large anticipatory saccades, and the frequency of leading saccades all deteriorate with increasing age. After correction for age, schizophrenic to control differences persist on most eye movement variables with the largest effect sizes for leading saccades (1.56) and smooth pursuit gain (1.17). Conclusions: The tendency to use saccades to anticipate target motion, even in small steps (leading saccades), deserves further attention as a potential marker useful in genetic analyses.