Visual Responsivity in Autism: Measuring Visual Responses in Autistic and Non-Autistic Adults Using Psychophysics, fMRI, and EEG.

Autistic individuals frequently report heightened sensitivity to visual stimuli, often described as discomfort in environments with bright or flickering lights. These experiences are hypothesized to reflect underlying differences in sensory gain or neural hyperexcitability; however, findings across studies have yielded mixed results, likely due to methodological variability. This study aimed to evaluate whether group differences in contrast-dependent neural and behavioral responses to a visual stimulus would be observed across complementary methods: psychophysics, fMRI, and EEG. Thirty-one autistic and twenty-seven non-autistic adults completed experimental sessions in which they passively viewed bilaterally presented 6 Hz counterphase flickering checkerboards at high (100%) and low (2%) contrast. Neural responses were measured using the blood oxygenation level-dependent (BOLD) signal from fMRI and steady-state visual evoked potential (SSVEP) from EEG. Contrast robustly modulated responses across experiments, eliciting higher neural responses; however, no group differences emerged in BOLD or behavioral thresholds. The only significant group difference was observed in SSVEP amplitudes, with autistic individuals showing significantly higher neural entrainment to the flickering stimulus than their non-autistic counterparts. Moreover, SSVEP amplitudes were associated with BOLD responses to the same low contrast visual stimulus, suggesting convergence between frequency-locked EEG responses and hemodynamic activity. SSVEP amplitudes were additionally associated with self-reported measures of hypersensitivity, linking heightened neural entrainment to individual differences in sensory experiences. They also showed a differential relationship with perceptual thresholds across groups. These findings show that differences between autistic and non-autistic participants were more evident in frequency-locked neural responses to periodic visual input, as measured by SSVEPs, and that these responses were meaningfully related to visual cortical BOLD activity and sensory hypersensitivity.