Impaired Auditory Habituation Correlates with Symptom Severity in Children with Autism Spectrum Disorder

Background: It is estimated that nearly 90% of all children with autism suffer from sensory abnormalities, often hypersensitivities, to stimuli that neuro-typical individuals could easily ignore (Leekam et al., 2007). However, empirical data show that these hypersensitivities are not caused by abnormally acute sensory capabilities (DePape et al., 2012; Bölte et al., 2012). Here, we consider habituation as an alternative account of hypersensitivities in autism, and investigate its relationship with behavioral traits. Habituation involves reduction of neural and behavioral response over the presentation of repeated, predictable stimuli. Our group recently proposed a theoretical account of autism as a disorder of prediction, positing that the ability to predict and therefore habituate to regular stimulus sequences would be reduced in autism.

Objectives: We aimed to investigate whether autism may be associated with reduced sensory habituation in the auditory domain, and the degree to which auditory habituation patterns correlate with behavioral characteristics.

Methods: To investigate whether habituation is indeed reduced in autism, EEG data were recorded from neurotypical (NT) and autistic children during 300 trials of repeated auditory tone bursts. ERPs were calculated for each subject in 50 trial segments using a sliding window. We calculated the line of best fit across successive potentials (amplitude) of the most prominent ERP peak using the least squares method. Slopes of the best-fit line for each subject were used to determine the habituation profiles for each participant, which were then correlated with the ADOS comparison score and other measures used for clinical characterization.

Results: Figure 1A shows sample ERP peaks and the best-fit line from one NT and one ASD participant in response to auditory tones. The NT participant shows gradual reduction in ERP amplitude over time, while the ASD participant shows a slight increase. The bar-plot (Figure 1B) shows the habituation slopes of individual ASD (n=9) and NT (n=21) participants. NT participants exhibit pronounced habituation, in contrast to those with ASD. ASD and NT groups show significant differences in their auditory habituation profiles (p=0.0078). Figure 1C shows that the rates of habituation in the ASD group are significantly (p<0.05) correlated with their ADOS scores with a Pearson correlation coefficient, r = 0.712. Conducting this analysis across multiple behavioral metrics reveals interesting groupings of those traits that are, or are not, significantly correlated with habituation rates.

Conclusions: The initial data support the hypothesis that autism is associated with reduced habituation to sensory stimuli and may help explain commonly observed features of ASD: sensory hypersensitivities (aversion to stimuli with negative valence) as well as restricted and repetitive interests (sustained engagement with positive valence stimuli). Furthermore, these results provide support for the broader hypothesis of impaired prediction in autism.