Hyper- or hypo-sensitivity to sensory stimuli are often observed in individuals with autism spectrum disorder (ASD). A number of different hypotheses have been proposed to explain the mechanisms that underlie these sensory issues, but findings have so far been mixed.

In the current study, SFARI Investigator Pawan Sinha and colleagues investigated one of these hypotheses, namely, that sensory habituation is altered in ASD. This work was supported by a SFARI Research Award and a pilot grant from the Massachusetts Institute of Technology Simons Center for the Social Brain.

In the study, children with (13) and without (22) autism of ages 7–13 years were presented with simple sensory stimuli (either auditory or visual) that did not have any social connotations and their electroencephalography data were concurrently recorded. Sinha and his team found the expected patterns of habituation, or attenuated neural responses over time, in typically developing children. By contrast, children with autism exhibited significantly reduced habituation in response to both auditory and visual stimuli. The fact that changes in habituation were observed across multiple sensory modalities suggests that the phenomenon may arise from central mechanisms that affect sensory processing across modalities, rather than from modality-specific peripheral factors.

Next, in an effort to understand the practical implications of the observed reduction in habituation, the researchers explored the relationship between neural habituation and clinical assessment of ASD. Their findings show significant correlations between the degree of habituation and social communication difficulties, as measured by the Social Communication Questionnaire (SCQ) — a parent report tool that is routinely used to screen for ASD. The extent of neural habituation also correlated with parents’ impressions of the severity of sensory differences, as measured by the Short Sensory Profile Second Edition (SSP-2). Thus, neural habituation appears to be behaviorally relevant in ASD.

If these correlations are found to replicate with additional cohorts of participants — and in particular, with children of a younger age — objective electrophysiological measures of sensory habituation may be valuable tools that clinicians could use, in combination with existing measures, to help assess ASD symptoms. Such data are relatively easy to collect and would help mitigate some of the biases inherent in parent or self-reports of behavioral symptoms.