Dissociating Visual Correlates of Context Modulation in ASD and Schizophrenia

Background: Theoretical and empirical accounts implicate altered contextual modulation as an underlying brain dysfunction in both ASD and schizophrenia spectrum disorders (SZS). Both disorders are also characterized by altered sensory processing, including differences in visual perception. In ASD, much attention has been paid to global-local interactions and perceptual biases, and in schizophrenia inability to filter information from the surround has been attributed to neural disinhibition associated with an excitatory/inhibitory imbalance. Contextual modulation reflects the way in which a visual feature is perceived dependent on the surrounding spatial context. There is some evidence that contextual modulation is impacted in both ASD and SZS; however, it has never been tested concurrently in both clinical populations.

Objectives: Examine behavioral correlates of visual context processing in young adults with ASD, in comparison to both adults with SZS and healthy controls.

Methods: Preliminary analyses included 9 adults with ASD, 9 with early-course SZS, and 14 controls, matched on relevant demographic variables. Recruitment is ongoing with an anticipated final sample size of 20 per group. Participants completed a visual contextual modulation battery (Fig.1). Following prior studies examining center-surround interactions (Yang et al., 2013), we used staircase procedures to measure psychophysical thresholds during forced choice comparisons of stimuli assessing surround modulations in: a) contrast, b) luminance, c) orientation, d) size. For each participant, the point of subjective equality (PSE) was computed for each task, quantifying the influence of the surrounding context. Group differences were assessed using one- and two-way ANOVAs.

Results: Across tasks, results revealed significant main effects of context (ps<0.001), indicating significant influence of the surrounding context (i.e., contextual modulation occurs) for all groups. In the orientation task, relative to controls, surround suppression was reduced in ASD but decreased in SZS (F=2.117, p=.13). In the Ebbinghaus (size) illusion, contextual effects on size perception were increased in ASD but decreased in SZS relative to controls (F=2.924, p=.07).  When comparing contrast, surround suppression was lower in both ASD and SZS relative to controls, though the interaction did not approach significance (F=1.254, p=.30). Finally, in the luminance task, neither individuals with ASD nor SZS showed differential surround suppression relative to controls (F=0.473, p=.63). Work is ongoing to relate patterns of context modulation to specific clinical features transdiagnostically.

Conclusions: Results revealed that patterns of contextual modulation differentiate ASD from SZS under specific conditions, whereas the two disorders are comparable in other contextual conditions. Specifics patterns of dissociation versus overlap may provide clues to underlying neural processes affected by context processing and neural excitation and inhibition within and across disorders. Future work directly measuring brain response during visual context processing will be crucial for teasing apart the extent to which this mechanisms characterizes ASD and related disorders where sensory, perceptual, and social deficits are key.