| dc.description.abstract | Impairments in inhibitory control (IC), or the ability to suppress a dominant behavioral response, are common in individuals with autism spectrum disorder (ASD). Multiple psychological and neurophysiological processes contribute to successful IC, though the extent to which these distinct processes are affected in ASD is not known. We previously have documented that individuals with ASD show a reduced ability to proactively delay response onset during a manual stop-signal task which contributes to failures inhibiting contextually inappropriate responses. Relative to manual movements, eye movements are highly automated, more difficult to inhibit, and more closely linked to discrete neurophysiological processes. Characterizing IC of eye movements in ASD may provide key insights into spared and affected psychological and neurophysiological processes. Sixty individuals with ASD aged 5-29 years and 63 age- and gender-matched typically developing controls completed an oculomotor stop-signal task (i.e., countermanding). During this task, the majority of trials were GO trials, on which participants made rapid eye movements (i.e., saccades) toward peripheral targets (12 degrees to the left or right of center). The remaining trials were STOP trials, on which a stop signal appeared at variable intervals following the peripheral target (i.e., stop signal delays) to cue the participant to inhibit the saccade. Stopping accuracy (i.e., the percent of STOP trials successfully inhibited), estimated reaction time of the stopping process (SSRT), and reaction time slowing on GO trials (GO RT slowing) compared to a baseline reaction time task were examined. Individuals with ASD exhibited reduced stopping accuracy and GO RT slowing and faster SSRTs compared to controls. For both groups, stopping accuracy was positively related to GO RT slowing and not related to SSRT. Increased age was associated with higher stopping accuracy and GO RT slowing, and these relationships did not differ across groups. The results indicate that individuals with ASD show a reduced ability to inhibit and proactively delay prepotent eye movements, while reactive stopping abilities are unaffected. Impaired IC was strongly and selectively associated with deficits in their ability to strategically delay response onset rather than reactively inhibit responses. These findings implicate reduced top-down control via fronto-striatal inhibition of brainstem circuitry in ASD, provide new targets for addressing clinical issues of IC, and suggest that tests of proactive control of eye movements may be useful for testing treatment efficacy and clarifying neurophysiological mechanisms of key clinical outcomes in ASD. | |
