Abstract
Purpose :
People with Autism Spectrum Disorder (ASD) often have abnormalities in adaptation, which is the ongoing recalibration of perceptual systems brought on by recent sensory encounters and that can be studied using a phenomenon known as perceptual hysteresis. Here we compared competition between perceptual adaptation and visual persistence processes at hierarchical levels of color perception and decision. Using psychophysical approaches we tested whether hysteresis occurs in color perception, and if so, what mechanism (adaptation or persistence) dominates; if it is affected by high level mechanisms (memory or binding) and lastly if there is an impaired balance between adaptation and visual persistence in ASD.
Methods :
We designed a color-matching paradigm using color changing stimuli in Blue-Green and Green-Red color axes, manipulated in cone space. Twenty two neurotypicals (NT) with the mean age of 25.2±4.0 years old and eight autistic participants with the mean age of 31.4±6.4 years old were recruited. Participants gave prior informed written consent, in accordance with the declaration of Helsinki, as approved by the Ethics Committee of the U. of Coimbra. We used direct or memory guided matching conditions requiring or not visual binding (Simple vs Compound stimuli). The task required comparison of the changing color to a target color and to press a button when their appearance matched. The difference between the target and the real reference color was estimated as a metric of hysteresis. For within-group statistical analysis we used parametric paired t-tests (NT) and Binomial tests (ASD) and between groups we used Non Parametric MANOVA.
Results :
In the NT group, negative hysteresis was present for simple matching (including memory) conditions (p<.001), showing that adaptation dominates over persistence which did also occur in the ASD group (p<.005). This effect disappeared when the stimulus conditions required local-global visual binding. According to our findings on ASD, there are no differences in adaptation between groups (p>0.05).
Conclusions :
We conclude that color perceptual decision-making shows negative hysteresis, with dominance of adaptation vs persistence, which is abolished when perceptual binding is required. Also, we found evidence for preserved adaptation mechanisms in ASD, which challenges the altered adaptation theory.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.