Autism spectrum disorders (ASD) are currently diagnosed on the basis of abnormal behavior within three core domains: (1) social skills, (2) communication skills, and (3) excessive restrictive/repetitive behaviors. Additional prominent characteristics often include deficits in sensory processing, motor coordination, and postural stability, which, we hypothesize, may be related to deficits in the vestibular system. The vestibular system has a large role in the "sense of balance," and it has a role in many involuntary reflexes. The vestibulo-ocular reflex, or VOR, is a reflex that helps to stabilize the surrounding visual scene during movement of the head and body by moving the eyes. The vestibular system translates information about head movements into signals that control the muscles for eye movement. These muscles then move the eyes in a manner that compensates for the amount of head movement, keeping the visual field stable. It has been known for about 40 years that the VOR differs between children who develop typically and children with ASD. However, very few studies have been conducted regarding vestibular deficits in this population. We have recently observed with a more modern eye movement measuring technique several abnormal qualities of the VOR, which appear to be unique to ASD, in a small sample of individuals tested during our preliminary study. The proposed study is to systematically study this reflex in ASD with a video-based eye movement tracking technique. The primary objective of this study is to thoroughly characterize the abnormal quality of the VOR in children with ASD, as compared to age-matched and nonverbal IQ-matched typically developing children. The secondary objective of this study is to compare measurements of VOR deficits to symptom severity as determined by measures of sensory processing, motor ability, restrictive/repetitive behaviors, and communication.
Impact: Many previous studies have clearly documented the neural circuitry controlling the vestibulo-ocular reflexes. The development of this neural circuitry and the development of the eye movement behaviors, and many of the genes that affect this development, have been well studied. Therefore, having a clear understanding of how this reflex is abnormal in ASD may help us to better understand the underlying abnormal neural mechanisms that might result in the more complex behaviors that characterize ASD such as social and communication skills or restrictive repetitive behaviors. Additionally, the VOR can be reliably measured in 2-6-month-old babies. Therefore, if we can distinguish which characteristics of the abnormal VOR observed in ASD are indeed specific to ASD, then VOR tests may be useful for identifying children at risk for ASD at a much younger age than would ever be possible using the classic diagnostic symptoms of ASD (i.e., deficits in social skills, communication skills, and repetitive behaviors). VOR can also be used as an outcome measure for visual and vestibular interventions commonly used in occupational therapy settings, and possibly as an indicator of which particular children might be more likely to benefit from vestibular interventions.