One characteristic of autism spectrum disorder (ASD) is sensory processing and abnormal brain function. Due to the differences in brain structures, behavioral and emotional problems arise. To register sensory information, the interpretation and encoding of immediate environmental information rely on multisensory integration (MSI) (Stickel et al. 2019). In ASD, the sensory processing is disturbed, leading to hyper or hyposensitivity to sensory input. This sensory dysfunction, resulting from the brain’s inability to interpret the sensory inputs, leads children to be highly sensitive to changes in daily routines (Kern et al. 2007). More easily put, the brain’s top-down processing, the prediction, combined with bottom-up sensory signals resolve the discrepancy between the prediction and the actual sensory information to minimize the future prediction errors (Coll et al. 2020). In individuals with ASD, the precision of top-down and bottom-up processing is altered, causing perceptual abnormalities, which in turn, shows the typical ASD characteristics such as sensitivity to sensory illusion or decreased sensory adaptation. Due to this susceptibility on sensory input, individuals with ASD insist on sameness and show repetitive movements (Coll et al. 2020). Even little changes become amplified and perceived as a tremendous change which often leads to discomfort. The alteration in sensory integration can be due to the abnormalities in white matter often found in individuals with ASD.
As a neurodevelopmental disorder, numerous ASD studies found that white matter in the brain is linked to social cognition. In order for humans to have such sophisticated social connections, larger brains, and more neurons, are required. To connect large areas of the brain, axons containing white matter becomes significantly important for neural communication. Although brain regions that are responsible for each sensory input and interpretation are crucial for recognition of each signal, white matter, responsible for trans-brain communication, might be more critical to social cognitive functions. Due to its widespread connection, small alteration or injuries to white matter can lead to social deficits. (Wang & Olson 2018). Studies have shown that abnormalities in white matter structure occur in individuals with ASD. Some earlier white matter studies, however, argue about the validity of the findings since individuals with ASD tend to move more in MRIs thus making the margin of error larger. Because of its role as a communication device for neurons, it affects sensory processing, anxiety, emotional distress, and potentially most of the brain function. As adaptive social behaviors and communications require rapid usage of multiple social skills, there is a huge pressure on the brain to quickly and efficiently process environmental information and react appropriately (Wang & Olson 2018). Due to the widespread abnormality of white matter structure, social cognition deficit can be easily predicted in individuals with ASD.
Coll, M.-P., Whelan, E., Catmur, C., & Bird, G. (2020). Autistic traits are associated with atypical precision-weighted integration of top-down and bottom-up neural signals. Cognition, 199, 104236. https://doi.org/10.1016/j.cognition.2020.104236
Kern, J. K., Trivedi, M. H., Grannemann, B. D., Garver, C. R., Johnson, D. G., Andrews, A. A., Savla, J. S., Mehta, J. A., & Schroeder, J. L. (2007). Sensory correlations in autism. Autism, 11(2), 123–134. https://doi.org/10.1177/1362361307075702
Stickel S, Weismann P, Kellermann T, et al. Audio-visual and olfactory-visual integration in healthy participants and subjects with autism spectrum disorder. Hum Brain Mapp. 2019;40(15):4470-4486. doi:10.1002/hbm.24715
Wang, Y., & Olson, I. R. (2018). The Original Social Network: White Matter and Social Cognition. Trends in Cognitive Sciences, 22(6), 504–516. https://doi.org/10.1016/j.tics.2018.03.005