The Relationship of Sensory Overresponsivity to Amplitude Discrimination

Background: Up to 95% of parents have reported differences in sensory processing for their child with ASD (Rogers & Ozonoff, 2005). An estimated 56 to 70% of youth with ASD meet criteria for sensory overresponsivity, defined as severe negative responses to sensory stimuli (Baranek et al., 2006; Ben-Sasson et al., 2007). Previous studies have suggested that hyperresponsivity is due to failure to habituate (Green et al., 2015). Use of vibrotactile methods can provide an objective, quantitative measure of tactile processing and adaptation.

Objectives: This study aims to relate performance on three amplitude discrimination tasks, two without adaptation and one with an adapting stimulus, to sensory overresponsivity in a group of typically developing (TD) children and children with ASD.

Methods: 42 children (21 TD, 21 ASD) matched on age and IQ completed a vibrotactile testing battery. For all three amplitude discrimination tasks, stimuli were delivered on two fingers of the left hand, with one of the stimuli having a higher amplitude. Participants were asked to determine which of the two stimuli had the higher amplitude. In the adaptation condition, each trial was preceded by an adapting stimulus delivered to a single site before the comparison stimulus, thus leveraging the effect of habituation. Parents of children completed the Sensory Profile (Dunn, 1999), which was used to measure sensory overresponsivity. Differences in amplitude discrimination task performance were investigated. A regression analysis was performed to determine whether sensory overresponsivity predicted task performance.

Results: There was a significant difference between amplitude discrimination with and without adaptation for TD children, but not for ASD children. Children with ASD had significantly greater sensory overresponsivity than did TD children. Sensory overresponsivity predicted performance on amplitude discrimination without adaptation for TD children, but did not significantly predict performance on any of the amplitude discrimination tasks for children with ASD.

Conclusions: Amplitude discrimination performance worsened with single-site adaptation for TD children, but not for ASD children, replicating previous research in this area. Children with ASD had higher sensory overresponsivity than did TD children; however, the restricted range of these values for children with ASD likely reduced the ability to predict amplitude discrimination performance. The performance of TD children with higher sensory overresponsivity appears to be less affected by the presence of an adapting stimulus, similar to that of children with ASD. These results may suggest that the level of sensory overresponsivity has a differential impact on adaptation.