Objectives: To investigate the neural correlates of potential coherent and biological motion processing deficits in adolescents with autism.
Methods: Coherent motion, biological motion and coherent form perception thresholds were measured psychophysically using the method of constant stimuli. Neural response to visual motion was measured during fMRI while participants viewed coherent and biological motion displays. Coherent motion perception was measured with random-dot displays where coherence was varied through a standard “random-walk” manipulation. Biological motion displays were point-light depictions of a person walking embedded in moving dot displays whose coherence was varied. Global form perception stimuli were static glass patterns whose coherence was varied based on the percentage of dots aligned along a global form.
Results: As a group, those with autism showed both higher coherent and biological motion thresholds while matching control group performance on the coherent form task. During fMRI scanning, the autism group showed reduced MT+, STS and parietal area activation while showing similar levels of activation in V1. Additionally, activation in MT+ and STS in control individuals steadily increased with increasing directional motion or biological motion coherence. No consistent relationship between psychophysical and neural responses was evident in data from individuals in the autism group.
Conclusions: These results provide evidence for a selective impairment in psychophysical and neural processing of visual motion in individuals with autism and highlight the possibility that deficits in visual processing may significantly contribute to the autism phenotype.