Subjects were 12 boys (12–14 yrs old) who had previously been diagnosed for hyperactivity (clinical group) and 15 age‐matched normal controls. For the selective attention (SA) task vertex ERPs were recorded to dichotically presented tone pips, with differing frequencies to each ear. Each series contained randomly interspersed signals and subjects were instructed to count the signals to one ear (targets). Behavioral tasks consisted of responses to SA targets, a 10‐min vigilance series, and dichotic listening. No significant group differences were found to non‐attended channels for N and P amplitudes and latencies. N amplitude enhancements to the attended channels were significant for the controls (44%), but not for the clinical boys (14%). Also, P latencies and amplitudes to the target pips were significantly greater for the control than the clinical group. Behavioral responses showed significant deficits by the clinical boys for SA and vigilance, but not for dichotic listening. Correct behavioral SA responses correlated significantly with P target amplitudes, but not with N amplitude enhancements. These findings indicate severe dysfunctions by the clinical boys for selective attention, involving both stimulus and response sets.

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Four monkeys were trained on an 8-sec. delayed-response (DR) task. Stimulating electrodes were implanted in frontal cortex and head of caudate, contralateral to the responding hand, and ipsilateral prefrontal cortex was ablated. Stimulation at constant-current settings, of 4-sec. or 2-sec. duration, was applied during discrete portions of the DR trial. For stimulation across the principal sulcus DR performance remained at 90% criterion level for application during intertrial and early cue-presentation period; it dropped to 70-80% correct when applied during the final second of cue presentation, or last 4 sec. of delay, but dropped to chance level only when applied during the first few seconds of the delay. Differing results were obtained for stimulation of other prefrontal or caudate structures. Stimulation did not affect acquisition or retention of visual discriminations.