Unreliable Evoked Responses in Autism

Autism has been described as a disorder of general neural processing, but the particular processing characteristics that might be abnormal in autism have mostly remained obscure. Here, we present evidence of one such characteristic: poor evoked response reliability. We compared cortical response amplitude and reliability (consistency across trials) in visual, auditory, and somatosensory cortices of high-functioning individuals with autism and controls. Mean response amplitudes were statistically indistinguishable across groups, yet trial-by-trial response reliability was significantly weaker in autism, yielding smaller signal-to-noise ratios in all sensory systems. Response reliability differences were evident only in evoked cortical responses and not in ongoing resting-state activity. These findings reveal that abnormally unreliable cortical responses, even to elementary nonsocial sensory stimuli, may represent a fundamental physiological alteration of neural processing in autism. The results motivate a critical expansion of autism research to determine whether (and how) basic neural processing properties such as reliability, plasticity, and adaptation/habituation are altered in autism. ► Poor response reliability was evident across multiple sensory systems in autism ► Larger variability was unique to evoked responses, not evident in ongoing activity ► Larger variability was specific to sensory areas and not shared across entire cortex ► Unreliable responses to basic stimuli that have little apparent social value Dinstein et al. present evidence that in autistic individuals brain responses to nonsocial stimuli are less reliable (noisier) across multiple sensory systems, suggesting that autism may be disorder characterized by widespread neural abnormalities, limited to social and cognitive areas.