Our goal was to use a series of electrophysiological metrics to assess the integrity of both magno- and parvo-cellular pathways among children with an ASD at both central and peripheral locations in relation to a group of typically developing children (TD).
We used two techniques, a standard visual evoked potentials (VEP) which contain information from both magno- and parvo-cellular pathways and the novel event-related potentials technique known as the VESPA (Visual Evoked spread Spectral Analysis). The VESPA allows us to bias stimulation towards either magno- or parvo-cellular pathways via the use of low and high contrast flickering stimuli respectively. Participants were asked to detect an infrequent target presented in the center of the screen to ensure that they were fixating, while checkerboards flickered at the appropriate contrast (VEP, magno and parvo VESPA). Stimulation was presented in both central and peripheral locations (at 6.3° visual angle). We synchronously recorded eye movements using high speed video eye tracker.
Both groups showed comparable evoked responses for centrally presented stimuli. At peripheral locations, parvo- VESPA were similar between groups, but the magnitude of the VEPs and magno- VESPA were much larger in the children with ASD than in the group of TD children.
Visual responses of children with ASD appear to be typical when stimuli are presented centrally. However, in the visual periphery, children with ASD showed a relatively typical parvo- and an atypical magno-cellular system response.