Heritability of different measures of smooth pursuit eye tracking dysfunction: A study of normal twins

Research studies have found that smooth pursuit eye movement dysfunction ma y serve as an index of genetic liability to develop schizophrenia. The heri tability of various measures of smooth pursuit eye tracking proficiency and the saccades that occur during smooth pursuit was examined in 64 monozygot ic (MZ) and 48 dizygotic (DZ) twin pairs. Two age cohorts were assessed (11 -12 and 17-18 years of age). Intraclass correlations indicated significant similarity in the MZ twins for almost all measures in both age cohorts, whe reas few of the DZ twin correlations attained significance. Biometrical mod eling indicated that genetic mechanisms influence performance on both globa l and specific eye tracking measures, accounting for about 40% to 60% of th e variance. These findings suggest that the underlying brain systems respon sible for smooth pursuit and saccade generation during pursuit are under pa rtial genetic control.