Sensory Gating and Sensory Processing in Children With High-Functioning Autism Spectrum Disorders

PURPOSE: Auditory processing is one of the most commonly reported sensory processing impairments in autism spectrum disorders. This study sought to determine whether children with high-functioning autism (HFA) differ from typically developing (TD) children on sensory gating, as measured by the P50 event-related potential (ERP) component. We also examined the association between sensory gating and sensory processing abilities.

RATIONALE: Sensory gating is a neurological process that filters out irrelevant stimuli, thus preventing sensory overload of higher brain functions. Although sensory processing dysfunction in children with HFA has been well documented in the literature, there is lack of converging evidence regarding sensory gating abilities in this group.

DESIGN: A cross-sectional quasi-experimental quantitative study design with convenience sampling procedures was employed to compare two groups.

PARTICIPANTS: Twenty-two children with HFA and 22 age- and gender-matched TD children, ages 5 to 12 yr, participated in this study.

METHOD: Electroencephalography was recorded while participants were presented with pairs of click stimuli. In the resulting ERP, the P50 component represents a positive deflection that occurs around 50 ms after stimulus presentation. It develops as a neuronal response to the conditioning (first) click while simultaneously activating inhibitory pathways. The reduction in amplitude of the P50 to the test (second) click compared with the conditioning click represents gating. The Short Sensory Profile (SSP) was used to assess sensory processing abilities.

ANALYSIS: Nonparametric statistics were used because the assumptions of normalcy were violated. To evaluate gating, the P50 amplitude of the test click and conditioning click were compared using a Wilcoxon signed ranks test for each group. Mann–Whitney U tests using test/conditioning (T/C) ratio and difference scores (test minus conditioning click) were performed to examine group differences. Spearman’s rho correlations were used to examine the association between the components of the SSP and the P50 difference scores.

RESULTS: For TD children, there was a significant reduction of the P50 amplitude of the test click compared to the conditioning click (Z = –3.91, p < .001), demonstrating significant gating, while no difference was found for children with HFA (Z = –0.37, p = .71). Mann–Whitney U tests revealed that children with HFA had significantly poorer gating than TD children for the T/C ratio (U = 91, p < .001) and difference scores (U = 65, p < .001). Additionally, P50 amplitude of the conditioning click was significantly smaller in children with HFA compared with TD children, suggesting deficits in orientation and early neural registration. Difference scores significantly correlated with all of the components of the SSP except Movement Sensitivity. Strongest correlations were found for Auditory Filtering and Total SSP score.

DISCUSSION: Results show that children with HFA display different brain processing mechanisms to auditory stimuli compared with TD children, especially filtering auditory stimuli. Moreover, neurological processing is strongly associated with sensory processing in everyday activities, suggesting that the sensory processing deficits observed in children with HFA may arise from atypical neurophysiological functioning related to gating.

IMPACT: These results can help practitioners understand the neurophysiological basis of behavioral manifestations of HFA, especially those atypical behaviors that occur in response to sensory experiences in everyday activities. Understanding the specific aspects of sensory processing that are a challenge for children with HFA may provide guidance to the types of treatment strategies that will be most effective.