Abstract
The signs of autism spectrum disorders (ASD)—lack of social communication, fixation, and repetitive action have to include visual perceptual abnormalities. Two theories currently attempt to explain the perceptual anomalies: the Weak Central Coherence (WCC) hypothesis and the Enhanced Perceptual Function (EPF) hypothesis. WCC developed from the observation of lack of Gestalt vision–with domination by local rather than global attentional processes. The EPF hypothesis proposed that individuals with ASD retain access to some local attentional processes that are supplanted by global processing in normals. The situation is complicated by dichotomies: magno/parvocellular pathways afferent to visual cortex, dorsal/ventral cortical streams, and global/local perception. Our study recruited 29 young adults displaying low, middle, or high autistic traits as measured by Baron-Cohen's Autism spectrum Quotient (AQ) and utilized motion coherence thresholds and nonlinear visual evoked potentials over a range of temporal luminance contrast levels from 10% to 95% to profile early cortical visual pathway function. Contrast response functions extracted from saturating second order kernel visual evoked potentials associated with magnocellular processing (first slice N60-P90) indicated higher magnocellular non-linear amplitudes for the high quotient group (compared with middle and low groups) indicating poor neural recovery to rapid stimulation. The non saturating second slice associated with Parvocellular processing (N95-P130) showed no difference between groups. The significantly higher contrast response function for the magno generated nonlinearities indicates that when driven hard, the magno system cannot recover as fast as in those medium or low in AQ. Together with observation of a higher amplitude non saturating first order N125-P160 amplitude for high AQ, we find physiological hints of both WCC and EPF. We are left with a conundrum: given the significant differences between those high and low in autistic tendency, what is “normal” when presenting data on the vision of neurotypical populations?