Visual cortical architecture in high-functioning autism spectrum disorders

Abstract

 

Previous research suggests enhanced local visual processing in individuals with autism spectrum disorders (ASD). Here we used population receptive field (pRF) analysis to test whether the fine-grained retinotopic architecture is atypical in individuals with high-functioning ASD (n=14) compared to neurotypical, demographically matched controls (n=12). We measured Blood Oxygenation Level Dependent (BOLD) responses using functional MRI while participants viewed traversing bar stimuli for retinotopic mapping. For each point in visual cortex we fitted a two-dimensional pRF model to the observed data that accounted both for excitatory and inhibitory effects on the BOLD response (Zuiderbaan et al., 2012, J.Vis. 12(3):10). Compared to controls, in the ASD group pRFs were larger in portions of extrastriate cortex representing the peri-foveal visual field. Further analyses showed that this was not due to differences in the shape of the hemodynamic response function or increased measurement noise. Interestingly, pRF sizes in ASD individuals also correlated with their autism quotient (AQ). In further experiments, outside the scanner, we tested the strength of the Ebbinghaus size illusion and the ability to discriminate orientation and global motion direction. ASD individuals were less able to tolerate directional uncertainty in global motion than controls but none of the behavioural measures were significantly related to the observed functional architecture of visual cortex. We propose that differences in pRF parameters may result from differential attentional deployment in ASD and this effect may be linked to the severity of behavioural symptoms in autism.

 

Meeting abstract presented at VSS 2013