Evidence for increased parvocellular and decreased magnocellular temporal response efficiencies in young adult autistic individuals.

Visual processing associated with an abnormal bias towards parvocellular dominated local perception rather than magnocellular dominated global form and motion perception is commonly reported in Autism Spectrum Disorder. However, to date, there has been little investigation into the physiological contributions of magnocellular and parvocellular pathways to V1 and their cognitive processing in clinically defined adult autism compared with typically developed controls. To investigate this, visual evoked potentials to a binary m-sequence stimulus presented foveally, were cortically recorded with high and low temporal contrast stimuli. Data were collected from 9 clinically diagnosed autistic young adults (some with comorbid intellectual disability), 5 individuals with intellectual disability who did not have autism and 42 young adults, and subjected to Weiner kernel nonlinear analysis. At low temporal contrast (24%) stimulation, first order responses of the clinical autistic and intellectual disability groups compared with the TD group demonstrate typically developing significantly reduced amplitudes in early first-order kernel peaks, while the second-order responses had relatively longer peak latencies. Neural efficiencies (amplitude ratios of first to second order peaks) of the magnocellular and parvocellular driven components showed significantly less efficient magnocellular pathway and more efficient parvocellular -pathway for the autistic group compared to the typically developing group F(1,44)=14.48, p<0.001. Thus, we suggest that the frequently reported autism preference for local over global perception is associated with the change in this balance of magnocellular and parvocellular neural efficiencies.