Atypical visio-temporal processing in schizophrenia and autism spectrum disorders revealed by the continuous wagon wheel illusion

Mental disorders such as schizophrenia and autism spectrum disorders (ASD) are mainly characterized by psychosocial dysfunction, but atypical perception is one of their additional common features that can provide important insight into the underlying psychopathological mechanisms. The observed abnormality of temporal processing in these patient populations has been proposed to reflect altered patterns of neuronal oscillatory synchrony. Here, we use the continuous version of the Wagon Wheel Illusion (c-WWI, in which observers report illusory reversals of a continuous, periodically moving stimulus, possibly caused by an oscillatory motion sampling mechanism), as a non-invasive behavioral approach to explore psychopathological changes in perception-related oscillatory synchrony patterns. Thus far, we have collected data from 4 groups: schizophrenia (n = 11), schizophrenia controls (n = 11), ASDs (n = 6), and ASD-controls (n = 6). Each participant watched computer-generated wheels (12 cycles of a sinusoidally modulated luminance pattern, 100% contrast) continuously rotating clockwise (or counter-clockwise) for 60 sec at the center of a CRT monitor (144 Hz refresh rate to minimize temporal framing artifacts); they continuously reported the perceived rotation direction. The c-WWI magnitude was measured as the relative duration of illusory motion perception. Temporal rotation frequencies were pseudorandomly selected from 2, 7, 10, 13, 16, 19, 21 Hz (4 trials each), and the actual rotation direction was randomized across trials. A 2-way ANOVA with factors "frequencies" and "group" (patients vs. controls) revealed a marginal interaction effect for the schizophrenia group (F_7,140 = 1.82, p = .17; c-WWI peaked at higher temporal frequencies in patients) and a significant interaction effect for the autism group (F_7,70 = 3.7, p <.05; c-WWI peaked at lower temporal frequencies in patients). Our preliminary results suggest that the c-WWI could be a powerful tool to non-invasively probe the relationship between temporal processing and neuronal oscillations in mental disorders.