Increased Eye-Blink Rate in Autism Spectrum Disorder May Reflect Dopaminergic Abnormalities

Background: Elevated blink rates have been related to overactivity of the central dopaminergic systems (Karson, 1983). In the only existing study of eye-blinks in autism spectrum disorder (ASD), Goldberg et al. (1987) found elevated blink rates in low-functioning children with ASD as compared to typically developing (TD) and developmentally delayed groups, suggesting that ASD may be associated with hyperactivity of the dopaminergic systems. While treatment success has been reported for dopamine blockers, definitive evidence regarding dopaminergic abnormalities in ASD is unavailable (Lam et al., 2005). Objectives: To examine blink rates in a group of high-functioning children with ASD in an effort to further elucidate potential abnormalities in dopaminergic activity. Methods: Participants were 14 children with ASD and 11 age- and NVIQ- matched TD children. Blinks were recorded during an Embedded Figures Test (EFT) using a binocular eye-tracking system. Time was divided into task (from trial onset until participant response) and inter-stimulus interval (ISI; from participant response until subsequent trial onset) for analysis of blink rates. Results: In the EFT, significant findings included a main effect of group and a condition (task, ISI) by group (ASD, TD) interaction. The ASD group had significantly higher blink rates than the TD group during the ISI, though not during task. Conclusions: Our findings show increased blink rate during task-free periods, which may suggest increased dopaminergic activity in children with ASD.