Investigating Physiological Measures of Early and Late Auditory Habituation in Autism Spectrum Disorder
AdvisorHutsler, Jeffrey J.
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Autism spectrum disorders (ASD) have long been defined as a combination of behavioral deficits which include impaired social interaction, impaired communication and repetitive behaviors (DSM-IV). Behavioral studies have identified both hypo- and hyper- responsiveness in autistic populations. Abnormal responsive patterns may affect one's ability to habituate to various types of stimuli in the environment. Previous studies of ASD subjects have found habituation failure to auditory stimuli. The goal of the current study was to evaluate early and late habituation to auditory stimuli with both auditory brainstem recording and galvanic skin response. In Experiment 1, auditory frequencies of 500, 2,000 and 12,000 Hz were presented at a constant stimulus intensity of 60 dB during a game condition. In Experiment 2, auditory frequency of 2,000 Hz was presented with a constant stimulus intensity of 60 dB during a reading condition. While reliable statistical significance wasn't achieved due to low sample size and methodological complications; physiological differences were identified. Experiment 1 auditory patterns indicated that ASD individuals tend to show higher slope values when collapsed across all three days compared to controls. Skin response measurements show that the sum velocity was substantially lower on day 2 of testing across both groups. In addition, frequencies of 500 HZ and 12,000 Hz showed the highest velocity values. In Experiment 2, total energy calculated for ASD individuals showed more total energy present in the responses to the second half of the tones than to the first half of the tones in ASD individuals to auditory stimuli. Slope values of the total energy indicate ASD individuals show increasing energy recorded at the electrode site as the tones continue to play, while control subjects tend to increase more slowly, not at all, or in fact decrease over time. Skin response measurements show that ASD tend to increase in velocity from the first half of the reading condition to the second while the control participants either stay roughly the same or decrease slightly. The current findings may shed light on the responsive patterns to auditory stimuli in ASD children. Future research should build upon the current study and take note of methodological issues in obtaining physiological measurements in ASD children.