A study building upon a decade of data collected on sensory responsiveness and multisensory speech perception and integration in children with autism spectrum disorder (ASD) confirms that neural measures of sensory function align with clinical measures of sensory sensitivity.
The findings were published in the Journal of Autism and Developmental Disorders in July with an extensive list of contributors* who made the study possible. The lead author on the paper is Jacob Feldman, a graduate student in the Biobehavioral Approaches in Neurodevelopment Laboratory at Vanderbilt, directed by Tiffany Woynaroski, Ph.D., assistant professor of Hearing & Speech Sciences and a VKC investigator.
Feldman says this may be the first study of its kind to confirm the link between neural and clinical measures of sensory differences in ASD.
“My mentor Tiffany Woynaroski and I are clinicians,” said Feldman. “We were interested in exploring whether clinical measures would align with experimental tasks. In our study, we gathered parent reports of sensory difficulties, using the Sensory Experiences Questionnaire and Sensory Profile Caregiver Questionnaire. For the experimental task, we had participants view videos that presented an audiovisual illusion prompting the McGurk effect.”
Feldman explains that the McGurk effect is like watching a dubbed movie. You can watch a movie that is dubbed and notice that the sounds you hear coming from the actors are not lining up with the movements of their lips. It feels perceptually off. The McGurk effect results from the brain trying its best to integrate the information coming in from multiple senses.
Feldman and Woynaroski looked at the responses of 18 children and adolescents (ages 8-17) with autism spectrum disorder and 18 matched typically developing peers who watched the videos and reported on what they perceived. In the videos, people pronounced four different syllables: “ba,” “da,” “ga,” and “tha.” The videos played in four different ways: auditory-only, visual-only (lip-reading), simultaneous audio-visual (same syllable heard and seen), and asynchronous audio-visual stimulus (different syllables heard and seen, meant to elicit the McGurk effect).
“For the asynchronous videos, we separated how far apart those two components were,” said Feldman. “We manipulated it so that sometimes the auditory would precede the visual by a certain amount of time and sometimes the visual would precede the auditory by a certain amount of time, because we believe that the length of time over which individuals bind the stimuli is very important.”
While children with ASD did not differ from the comparison group when the audio and visuals were presented simultaneously, differences became more apparent when the audio and visuals were not in harmony. In general, the researchers found that children with ASD with fewer sensory challenges (as reported by parents) were more accurate across all of the video tasks. For example, the more sensitive to sensory stimuli individuals were, the lower their ability was to distinguish between syllables in each condition.
“In previous research**, we noticed that when we increased the amount of difference and looked over the whole window of time that we presented these asynchronies, the children with ASD reported perceiving the fused illusion effect over longer periods of time,” said Feldman. “This is not ideal, because the brain is only supposed to handle a certain amount of ambiguity.”
VKC investigator Mark Wallace, Ph.D., Louise B. McGavock Endowed Chair, professor of Hearing & Speech Sciences, and Dean of Vanderbilt University Graduate School, explained why this longer window of time can be problematic.
“In an ordinary conversation with a friend, for example, the brain must rapidly and accurately bind together the sound of your friend’s voice with the images of her mouth moving, as well as any other visual and auditory cues from her body,” said Wallace.
“The auditory information arrives as ‘phonemes,’ units of sound that make up a word. The visual cues come in the form of ‘visemes,’ the visual cues (as when lip-reading) that match up to phonemes. This matching is one-to-one in someone with good speech comprehension, but if the window is too long, it becomes one-to-several—and the quality of the communication deteriorates. We know from previous research that the longer the binding window is in people with autism, the poorer they perform on tasks that require them to connect auditory and visual information.”
In this study, longer binding windows were associated with greater sensory challenges, as reported by parents. More clinically significant sensory symptoms were associated with longer binding windows.
Feldman says we still do not know whether children with ASD show the clinical characteristics first that then cause them to have significant audiovisual integration challenges, or whether perceptual difference occurs first, which then causes the clinical symptoms to occur.
“We want to look at these responses over time and see what changes,” said Feldman. “What occurs first? And then, more importantly, we want to identify whether these differences are foundational to the sensory challenges we see in ASD.
“The good news from this study is that the findings from the clinical measures did align with the experimental task, opening up new directions from which to address these issues. A lot of people are excited because we are bridging these two areas together. These findings could be very promising for developing new interventions to train children on audiovisual integration, which might help ease their sensory issues.”
Courtney Taylor is VKC associate director of Communications and Dissemination.
*Feldman, J. I., Kuang, W., Conrad, J. G., Tu, A., Santapuram, P., Simon, D. M., Foss-Feig, J. H., Kwakye, L. D., Stevenson, R. A., Wallace, M. T., &Woynaroski, T. G. (2018). Brief report: Differences in multisensory integration covary with sensory responsiveness in children with and without autism spectrum disorder, Journal of Autism and Developmental Disorders. (Jul 24), pp 1–7.
**Woynaroski, T. G., Kwakye, L. D., Foss-Feig, J. H., Stevenson, R. A., Stone, W. L., & Wallace, M. T. (2013). Multisensory speech perception in children with autism spectrum disorders. Journal of Autism and Developmental Disorders, 43, 2891-2902. doi:10.1007/s10803-013-1836-5