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 ha s been proposed as a marker of genetic risk for schizophrenia, although the precise component of SPEM tracking most associated with genetic risk remai ns undetermined Normal adult aging is associated with deterioration on SPEM tasks; it remains unclear whether investigations of SPEM abnormalities wil l allow inclusion of older subjects in genetic studies. This study examines 1) the effect of normal aging on several components of SPEM performance; a nd 2) whether schizophrenic-normal differences found in young adults contin ue over a broad adult age span. Methods: SPEM was recorded during a 16.7 degrees per sec constant velocity task in 64 normal adults, ages 18 to 79 years, and 58 schizophrenic subject s, ages 18 to 70 years. Results: Smooth pursuit gain, the percent of total eye movements due to cat ch-up saccades, the frequency of large anticipatory saccades, and the frequ ency of leading saccades all deteriorate with increasing age. After correct ion for age, schizophrenic to control differences persist on most eye movem ent variables with the largest effect sizes for leading saccades (1.56) and smooth pursuit gain. Conclusions: The tendency to use saccades to anticipate target motion, even in small steps (leading saccades), deserves further attention as a potenti al marker useful in genetic analyses, Biol Psychiatry 1999;46:383-391 (C) 1 999 Society of Biological Psychiatry.