Daniela L Seczon¹, Hannah M Rea¹, Kristin M Woodard¹, Tamar Kolodny², Sara J Webb^1,3, Scott O Murray¹; ¹University of Washington, ²Ben-Gurion University of the Negev, ³Seattle Children's Research Institute

Visual sensory processing in autism is often characterized by heightened sensitivity, which may be a product of increased neural responses to visual stimuli. To investigate these behavioral and neural responses, we integrated three measurement techniques—fMRI, EEG, and psychophysics. Twenty-seven autistic and thirty-one non-autistic adults completed experiments that used a consistent visual stimulus across all methods; bilaterally presented circular counterphase 6Hz-flickering checkerboards, in high (100%) and low (2%) contrast conditions. For fMRI and EEG sessions, participants fixated on the center of the screen and the bilateral checkerboards were presented following a design that alternated 10 seconds of stimulus with 20 seconds of blank-fixation. For fMRI, responses were measured in retinotopically-defined regions of early visual cortex including V1, V2, and V3. For EEG, steady-state visual evoked potentials (SSVEPs) amplitudes were extracted and analyzed for peak amplitudes across a pre-selected set of electrodes. During the psychophysics experiment, participants underwent three versions of a detection task: no adapter, low contrast adapter, and high contrast adapter conditions. Adapter conditions presented the flickering checkerboards before a subsequent lateralized target checkerboard in one of the two (left or right) hemifields. The target’s contrast was adjusted following a staircase procedure, and behavioral data were extracted to estimate individual contrast detection thresholds. Stimulus contrast had a significant effect across experiments; the high contrast condition elicited greater fMRI and SSVEP responses, and the high contrast adapter led to higher contrast detection thresholds. Significant group differences emerged in SSVEP responses, with autistic individuals exhibiting higher amplitudes across both contrast conditions. Contrastingly, groups had comparable BOLD responses and contrast detection thresholds. This study provides some evidence that autistic individuals show heightened neural activity to visual input, as measured by SSVEPs, but these differences do not translate to differences in behavioral or hemodynamic responses.

Acknowledgements: NIH R01MH118847 and SFARI 647415 to SOM and SJW