Examining Habituation in ERP Responses to Auditory Processing in Children with Autism

Background: Unusual sensory experiences are increasingly identified as a key characteristic of individuals with autism spectrum disorder (ASD)(Baranek et al., 2006), and have been included in the diagnostic criteria for the disorder in the Diagnostic and Statistical Manual V (American Psychiatric Association, 2013). In previous work, we examined event-related potential (ERP) responses to auditory stimuli in children with ASD and matched neurotypical children and found attenuated neural responses in ASD (Donkers et al., in press). However, the adaptability of these neural processes in ASD remains to be examined. In neurotypical individuals, ERPs have been shown to habituate (or attenuate) in response to repeated presentations of stimuli (e.g., Romero et al., 1996), reflecting adaptation to external sensory stimuli. Previous functional magnetic resonance imaging research has shown evidence of impaired neural adaptation in adults with ASD (Schipul et al., 2012). Here, we sought to determine if neural habituation, as reflected in ERP responses, is impaired in children with ASD.

Objectives: The current study examines changes in ERPs in response to repeated presentation of auditory stimuli in children with ASD and matched neurotypical (NT) children, in order to gain insight into the adaptability of neural processes in this population.

Methods: Participants include children with ASD and NT children (4-12 years of age). ERPs were collected during a passive listening task, consisting of 5 blocks of standard tones and intermittent novel sounds. Data was collected from 11 electrode sites and was analyzed using EEGLab and FieldTrip MATLAB functions. ERP components examined include (1) the P1, reflecting early sensory processes; (2) the N1/N2, reflecting pre-attentive perceptual processes; and (3) the P3a, reflecting post-sensory attentional processes. ERPs were compared between blocks 1-2 and blocks 4-5 of the experiment in order to assess change over time.

Results: Preliminary results suggest that the NT group (n=10) shows greater changes over time in the P3a in response to novel sounds, as compared to the ASD group (n=10).  This finding suggests that children with ASD show less habituation in attentional orienting processes in response to novel stimuli.  Group differences are not significant with this sample size in the earlier, sensory ERPs to standard tones (P1, N1/N2). Final analyses will include data from an additional 18 children with ASD and 27 NT children that has already been collected, increasing power to find differences in the P1 and N1/N2, which are characterized by smaller effect sizes.

Conclusions: These preliminary findings suggest reduced habituation in attentional ERP responses to auditory stimuli in ASD, possibly reflecting reduced neural adaptability in the disorder. This work suggests that children with ASD may be less able than NT children to adapt to repeated sensory stimuli, which may have implications for our understanding of sensory hyperresponsivity in ASD. Further analyses with our complete sample size will have more power to examine habituation effects in earlier, sensory neural processes (P1 and N1/N2 ERPs).  This work has the potential to inform our understanding of the adaptability of neural responses in children with ASD, which in turn may impact treatment.