Visual orientation processing in autism spectrum disorder: No sign of enhanced early cortical function.

It has been suggested that enhanced perceptual processing underlies some of the social difficulties associated with autism spectrum disorder (ASD). While a variety of visual tasks have been reported in which individuals with ASD outperform neurotypical individuals in control groups, the precise origin of such effects within the visual pathway remains unclear. It has recently been established that visual acuity is intact yet unremarkable in ASD. This suggests that the earliest levels of retinal processing are an unlikely candidate as the source of differences. The next potential levels for divergent visual processing are those involved in processing simple aspects of visual stimuli, such as orientation and spatial frequency, considered to be functions of early visual cortex. Here we focused on the basic processing of orientation. In three experiments, we assessed three basic aspects of orientation processing-discrimination, veridical perception, and detection-in participants with ASD in comparison to age-, gender-, and IQ-matched adults without ASD. Each experiment allowed for both qualitative and quantitative comparisons between the two groups. These provided a dense array of data indicating that participants with ASD perceive orientation of low-level stimuli in a qualitatively (as well as quantitatively) similar manner to participants without ASD in control groups, with no evidence of superior processing in detection, precision, or accuracy aspects of orientation perception. These results suggest that the source for altered perceptual abilities should be sought elsewhere, possibly in specific subgroups of people with ASD, other aspects of low-level vision such as spatial frequency, or subsequent levels of visual processing.