Visual tracking and motion analysis in autism: Severity and laterality of sensory and sensorimotor deficits

Oculomotor studies in autism provide novel strategies for evaluating the functional integrity of multiple brain areas because the relevant circuitry has been well established. Visual pursuit of high-functioning autistic individuals and IQ and age matched healthy participants was compared using pure ramp, step ramp and oscillating target tasks. Autistic individuals had comparable pursuit latency to healthy individuals, but demonstrated slower sustained pursuit when tracking both oscillating and ramp targets. The deficit is consistent with a disturbance in the frontocerebellar loop, and the deficit was larger in older participants indicating a maturational failure of this particular circuitry. Additionally, initial “open loop” pursuit was slower in autistic individuals only when targets were moving into the right visual field. Because of the high reliance on sensory information in the open-loop pursuit, visual motion processing in individuals with autism was also examined, but no impairment was found in velocity discrimination and the perception of motion-defined forms. Thus, the unilateral pursuit deficits are likely to reflect problem in transferring information from the left posterior sensory areas to motor areas rather than sensory disturbances.; Because pursuit eye movements place high demands on coordination of sensory, cognitive and motor processes subserved by a widely distributed brain system, visual pursuit deficits in autism indicate disturbances in interregional communication in the brain to meet the demands of the pursuit tasks. This type of disturbance seems particularly pronounced in the frontocerebellar loop and left frontoparietal connections reflected in slower pursuit of predictable.; targets and poor initial “open-loop” pursuit when targets moved into the right visual field. The current findings suggest intact visual motion processing in autism that is mediated by a relatively localized mechanism at the cost of more global and integrative processing that depends on the coordination of activities in many brain areas, such as visual pursuit. This performance profile is consistent with the local over global information processing style that is proposed by the central coherence theory of autism.