Reduced Habituation to Naturalistic Stimuli in Autism

Background: Habituation plays a fundamental role in processing changing saliencies of environmental stimuli. Impaired habituation reduces stimulus suppression, immersing an individual in an unrelentingly salient, and potentially overwhelming, world. It would also compromise the ability to 'detach' attention from a stimulus. Impairments in habituation could account for sensory hypersensitivities as well as sustained interest in circumscribed stimuli, two prominent features of the autism (ASD) phenotype. Objectives: In prior work, we showed that habituation to low-level sensory stimuli (metronomic auditory sequences) is reduced in autistic participants compared with controls. This study investigates habituation to naturalistic audiovisual stimuli. Methods: We recorded the galvanic skin response (GSR) to repeated presentations of naturalistic video stimuli. Participants were shown 1 minute of neutral baseline stimuli, followed by five repetitions of a 30s video clip. Results: We found consistent differences in the time-course of GSR signals from ASD participants compared with age-matched neurotypical controls. For controls, GSR signals over time consistently showed a decreasing trend, indicating habituation. Conversely, for the ASD group, the GSR signals over time showed a relatively flat or increasing trend, indicating compromised habituation. Conclusions: These results may help to explain prominent features in ASD: sensory sensitivities, restricted and repetitive interests and associated behaviors such as repetitive intake of media. We argue that these findings are not due to extraneous factors such as general arousal levels, agitation, movement, or inattention, although further study is required. Future investigations will assess habituation profiles in infancy, the specificity of impaired habituation in autism compared with other conditions, and in modalities other than vision. At this stage, however, the consistency of our results across a wide range of ages and cognitive abilities points towards reduced habituation as a possible endophenotype that may yield better understanding of some key aspects of the autism phenotype. Meeting abstract presented at VSS 2016