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Lilach Shalev, Yarden Dody, Carmel Mevorach; Impaired selection- and response-related mechanisms in adult-ADHD. Journal of Vision 2010;10(7):284. doi: 10.1167/10.7.284.
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A substantial amount of research has been directed at identifying the neurocognitive processes responsible for the inattentive, hyperactive, and impulsive behaviors observed in children and adults with attention deficit/hyperactivity disorder (ADHD). Of the many potential cognitive processes that have been suggested, a large body of evidence points to impairments in executive functions. The present study focuses on response suppression and on executive control in adults with and without ADHD using a global-local task with a manipulation of saliency (Mevorach, Humphreys & Shalev, 2006b). This task enables us to separate out three types of effects: effects reflecting the selection of local and global elements in displays, effects reflecting the ability to attend to the more or less salient aspects of a display and effects reflecting the ability to filter out irrelevant incongruent information. Participants with ADHD demonstrated an exaggerated effect of relative saliency. Typically, interference from the distractor is greater when the target is low in saliency and the distractor high in saliency, compared with when the target has high saliency and the distractor low. In individuals with ADHD this bias towards high saliency stimuli, and the difficulty in attending to low saliency stimuli, was greater than in the control participants. In addition, the ADHD group yielded an increased congruity effect compared to the control group. That is, participants with ADHD showed more difficulties in filtering out irrelevant incongruent information. The former effect represents a difficulty in selection mechanisms whereas the latter effect represents a difficulty in response related mechanisms in adult-ADHD.
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