Normal binocular rivalry in autism: Implications for the excitation/inhibition imbalance hypothesis

Autism is characterized by disruption in multiple dimensions of perception, emotion, language and social cognition. Many hypotheses for the underlying neurophysiological basis have been proposed. Among these is the excitation/inhibition (E/I) imbalance hypothesis, which states that levels of cortical excitation and inhibition are disrupted in autism. We tested this theory in the visual system, because vision is one of the better understood systems in neuroscience, and because the E/I imbalance theory has been proposed to explain hypersensitivity to sensory stimuli in autism. We conducted two experiments on binocular rivalry, a well-studied psychophysical phenomenon that depends critically on excitation and inhibition levels in cortex. Using a computational model, we made specific predictions about how imbalances in excitation and inhibition levels would affect perception during two aspects of binocular rivalry: mixed perception (Experiment 1) and traveling waves (Experiment 2). We found no significant differences in either of these phenomena between high-functioning adults with autism and controls, and no evidence for a relationship between these measurements and the severity of autism. These results do not conclusively rule out an excitation/inhibition imbalance in the visual system of those with autism, but they suggest that such an imbalance, if it exists, is likely to be small in magnitude.

► Autism is characterized by disruptions in behavior, social cognition, and perception. ► One proposed cause of autism is a putative imbalance in excitation and inhibition. ► Binocular rivalry depends critically on levels of cortical excitation and inhibition. ► We found normal binocular rivalry and normal traveling waves in autism. ► These results cast doubt on the excitation/inhibition imbalance theory of autism.