Selective Attention in Hyperactive Children Responsive to Methylphenidate

Electrophysiological measures of cortical activity have indicated that hyperactive children who show a positive response to methylphenidate may have a deficit in inhibitory innervation. It has been suggested that this deficit may occur in the sensory and motor systems and result in two major symptoms of hyperactivity, poor attention and excessive motor activity. In this experiment sensory inhibition was evaluated for hyperactive and normal subjects using a shadowing task with various types of distractors. It was hypothesized that if attentional deficits of hyperactive subjects were due to their inability to inhibit irrelevant sensory input, then shadowing performance for the hyperactive group should be equivalent to the performance of controls when no distractor was present, but inferior when speech was the distractor. In addition, it was hypothesized that methylphenidate should increase accuracy of shadowing performance for hyperactive subjects. Errors of omission were used as the dependent measure. It was found that overall hyperactive subjects did more poorly than controls on shadowing letters under all three distractor conditions tests: no distractor, white noise, and speech. In addition, the interference during the three conditions was found to be different with speech being the most disruptive and white noise and no distractor being equivalent. Neither the hypothesis of increased interference for hyperactive subjects with increased sensory input nor the hypothesis of improved performance with medication for the hyperactive children was supported. The lack of significance of these two tests must be qualified by the fact that a ceiling effect was found in the data. It was concluded that in this experiment hyperactive subjects demonstrated an attentional deficit when compared to normal subjects and that this deficit was not related to sensory input. However, conclusions cannot be made concerning the effect of medication or sensory input on hyperactive children\u27s attention because of the ceiling effects in the data