What does distractibility in ADHD reveal about mechanismsfor top-down attentional control?

摘要

In this study, we attempted to clarify whether distractibility in ADHD might arise fromincreased sensory-driven interference or from inefficient top-down control. We employedan attentional filtering paradigm in which discrimination difficulty and distractor salience(amount of image "graying") were parametrically manipulated. Increased discriminationdifficulty should add to the load of top-down processes, whereas increased distractor sal-ience should produce stronger sensory interference. We found an unexpected interactionof discrimination difficulty and distractor salience. For difficult discriminations, ADHD chil-dren filtered distractors as efficiently as healthy children and adults; as expected, all threegroups were slower to respond with high vs. low salience distractors. In contrast, for easydiscriminations, robust between-group differences emerged: ADHD children were muchslower and made more errors than either healthy children or adults. For easy discrimina-tions, healthy children and adults filtered out high salience distractors as easily as low sal-ience distractors, but ADHD children were slower to respond on trials with low saliencedistractors than they did on trials with high salience distractors. These initial results froma small sample of ADHD children have implications for models of attentional control, andways in which it can malfunction. The fact that ADHD children exhibited efficient atten-tional filtering when task demands were high, but showed deficient and atypical distractorfiltering under low task demands suggests that attention deficits in ADHD may stem from afailure to efficiently engage top-down control rather than an inability to implement filter-ing in sensory processing regions.