Perceptual and neural correlates of tactile processing and relationship to sub-clinical autism traits
Bryant, Lauren Kay
One fundamental objective of neuroscience research is to determine how aspects of a sensory stimulus are encoded and processed—from periphery to cortex. The answer to this question not only provides foundational knowledge of typical sensory processing, it is also crucial for our understanding of the behavioral manifestations of sensory dysfunction frequently noted in autism spectrum disorders (ASD). The two original studies detailed in this dissertation use complementary self-report, observational, psychophysical and neuroimaging methods to address the perceptual and neural correlates of vibrotactile intensity processing and their relation to autism traits in the neurotypical population. A narrow psychophysical tactile dynamic range was associated with increased autism-related traits in individuals who reported greater sensory hypersensitivity. In contrast, in individuals less prone to sensory hypersensitivity, a narrow dynamic range was associated with reduced autism-related traits. Functional Magnetic Resonance Imaging (fMRI) data provide preliminary evidence that disproportionate neural responses to suprathreshold vibrotactile stimuli of increasing intensity predict tactile psychophysical performance and autism-related traits in neurotypical adults. Collectively, study findings represent a significant step towards understanding the mechanisms involved in normative sensory differences and how they relate to the autism phenotype. The significance of our results encourages the growing perspective that neural mechanisms might be better clarified by splitting groups not by a clinical label, such as ASD, but by a narrower autism-related construct of interest, such as tactile sensitive versus sensory typical. Findings also highlight the importance of considering dynamic behavioral and neural metrics capable of illustrating how an individual’s response changes as a result of discrete changes in a feature of a sensory stimulus.