Neurophysiological Correlates of Sensory-Based Subtypes in Autism

PURPOSE: Children with autism spectrum disorder (ASD) often present with atypical responses to sensory stimuli (Reynolds, Lane, & Thacker, 2012). Additionally, this population has shown differences in autonomic nervous system activity as well as neuroendocrine response during the presentation of sensory challenges. Sensory-based subtypes have been developed to create more homogenous autism subgroups that may also differ physiologically. One such system, created using both type of responsivity (hypersensitivity, hyposensitivity, sensory seeking) and sensory domain, shows initial promise (Lane, Molloy, & Bishop, 2014). However, differences in nervous system response to sensory input between these sensory-based subtypes is unexplored. This study used indices of neuroendocrine (salivary cortisol) and autonomic nervous system activity (skin conductance level and respiratory sinus arrhythmia [RSA]), to answer the following research question: Can sensory-based ASD subtypes be distinguished by patterns of autonomic nervous system and neuroendocrine measures?

DESIGN: This retrospective study used secondary data from two university-based research groups. Participants from the combined data were categorized into one of four different sensory-based subtypes. Neurophysiological measurements previously recorded during the Sensory Challenge Protocol (SCP) as well as baseline measures pre-SCP were then compared between each subtype.

METHOD: Original data were collected on 86 children with autism ages 6–12 yr during administration of the SCP. The SCP is a systematic approach for delivering eight repetitions each of six different sensory inputs (tone, olfactory, visual, auditory, tactile, vestibular; McIntosh, Miller, Shyu, & Hagerman, 1999). This protocol allows physiological response data to be associated with specific stimuli. Electrodes on the hands and chest captured RSA and skin conductance responses, while saliva samples were used for cortisol analysis (Reynolds et al., 2012). Quantitative analyses included between-group comparisons (repeated-measures analysis of variance and multivariate analysis of variance) and logistic regression to examine predictors of subtype membership. Dependent variables were cortisol, skin conductance, and RSA, and the independent variable was subtype membership (four independent subtypes).

RESULTS: The primary finding was that RSA was able to differentiate subtypes with typical versus atypical sensory responsivity. Differences were found during baseline RSA and also during tone, tactile, and movement stimuli (p < .05). Additionally, membership in certain subtypes was predicted by RSA during auditory stimuli and during recovery periods (p < .05). Small sample size from secondary data and measurements available for each participant were substantial limitations for the analyses.

CONCLUSION: The selected subtyping system, based on behavioral observations of sensory responsivity, may not distinguish neurophysiological differences within the autism population. It is also possible that these neurophysiological markers do not fully reflect the complex response of the nervous system to multisensory inputs in the natural environment. Patterns of neurophysiological response, rather than isolated responses to individual sensory stimuli, may better distinguish different subgroups and be more useful for diagnosis and treatment planning.

IMPACT STATEMENT: This research is significant to the field of occupational therapy because it provides further evidence that children with sensory processing disorders demonstrate different neurophysiological responses to sensation from typically developing children. However, results also suggest that a new subtyping approach may be necessary. Additional research is needed to explore the merits of behavior-based sensory subtypes in relation to neurophysiological response patterns.

References

Lane, A. E., Molloy, C. A., & Bishop, S. L. (2014). Classification of children with autism spectrum disorder by sensory subtype: A case for sensory-based phenotypes. Autism Research, 7, 322–333. https://doi.org/10.1002/aur.1368

McIntosh, D. N., Miller, L. J., Shyu, V., & Hagerman, R. J. (1999). Sensory-modulation disruption, electrodermal responses, and functional behaviors. Developmental Medicine and Child Neurology, 41, 608–615. https://doi.org/10.1111/j.1469-8749.1999.tb00664.x

Reynolds, S., Lane, S. J., & Thacker, L. (2012). Sensory processing, physiological stress, and sleep behaviors in children with and without autism spectrum disorders. OTJR: Occupation, Participation and Health, 32, 246–257. https://doi.org/10.3928/15394492-20110513-02

Schaaf, R. C., Benevides, T. W., Leiby, B. E., & Sendecki, J. A. (2013). Autonomic dysregulation during sensory stimulation in children with autism spectrum disorder. Journal of Autism and Developmental Disorders, 45, 461–472. https://doi.org/10.1007/s10803-013-1924-6