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Objective: To compare the effects of methylphenidate on attention-deficit/hyperactivity disorder (ADHD) subtypes., Method: Nineteen ADHD/inattentive (ADHD/I) and 22 ADHD/combined (ADHD/C) 6- to 12-year-old children entered a 6-week, double-blind trial of placebo and methylphenidate in divided doses (0.94 +/- 0.02 mg/kg/day = 33.06 +/- 1.40 mg/day). ADHD children received a restricted arithmetic task without medication before the trial and after their noon dose on the last day of each phase. Thirty-four unmedicated controls were tested at comparable time points. Parents and teachers rated ADHD children before and after each phase of the trial; parents rated controls before the study., Results: Controls had marginally better arithmetic performance than children with ADHD/C who outperformed ADHD/I children. Unmedicated children with ADHD exceeded controls in task-incompatible behaviors during restricted arithmetic. Under methylphenidate, both ADHD subtypes reached control levels of arithmetic performance and task-incompatible behavior. Before the trial, parents rated children with both ADHD subtypes higher than controls on inattention, hyperactivity, and oppositionality/aggression and parents and teachers rated ADHD/C children higher than ADHD/I children on hyperactivity and oppositionality/aggression but not inattention. Methylphenidate lowered parent and teacher ratings of inattention and hyperactivity for those with both ADHD subtypes, but ratings of children with ADHD/C decreased more in hyperactivity and aggression., Conclusions: Methylphenidate ameliorated task-incompatible behavior, arithmetic performance, and inattention comparably in both ADHD subtypes, whereas medication reduced hyperactivity and aggression largely in children with ADHD/C.

Objective: The undertreatment of ethnic minority children with ADHD prompted a study on the effects of methylphenidate (MPH) on the executive functions of African American children with ADHD., Method: Nineteen African American children with ADHD are tested on the Tower of Hanoi (TOH) and the Paired Associates Learning Task (PAL) in a double-blind crossover acute challenge of MPH and placebo., Results: Under MPH, TOH rule breaks decrease, especially in the second testing session, and TOH planning time increases, particularly for incorrect solutions; PAL recall in the final learning trial improves with MPH., Conclusion: Similar to previous findings with predominantly majority samples of patients with ADHD, MPH enhances planning, precision, and persistence in African American children with ADHD.

We administered the Tower of Hanoi to demographically comparable samples of control participants (n = 34) and children with the Combined (n = 22) and Inattentive subtypes (n = 19) of Attention-Deficit/Hyperactivity Disorder (ADHD). Controls excelled over children with the Inattentive subtype, who outperformed patients with the Combined subtype. These results replicated findings of greater executive deficits in the Combined than in the Inattentive type of ADHD. Double-blind administration of methylphenidate improved task performance only for patients with the Inattentive subtype. In a drug-free Baseline session, children with both subtypes of ADHD made more private verbalizations than controls, particularly when failing puzzles. In later sessions, regardless of drug condition, the inattentive sample exhibited a smaller increase in self-regulatory utterances under failure. In contrast, the combined sample decreased self-regulatory verbalizations under failure only under methylphenidate. The results support some differences between the two subtypes of ADHD in executive functioning and in their response to stimulant therapy.

Twenty-six children with attention deficit/hyperactivity disorder (ADHD) participated in a double-blind trial consisting of 2 consecutive weeks each of placebo and methylphenidate (M = 26.92 mg/day = 0.78 mg/kg/day). As expected, stimulant therapy resulted in moderate weight loss, increased somatic complaints, and teacher and parent reports of reduced inattentiveness, aggression, and oppositionality. In both phases of the trial, patients were tested in a choice reaction time task assessing two aspects of the task that presumably affect response selection: response frequency (ratio of targets/nontargets = 25/75 vs. 50/50) and stimulus sequence (alternations vs. repetitions). Both manipulations yielded expected results on performance and event-related potentials (ERPs). Stimulant treatment increased accuracy and speed among younger children and curtailed variability of reaction time for the sample as a whole. However, methylphenidate did not affect ERPs. In combination, the results imply that the enhancement of performance by methylphenidate does not involve the demands of response selection examined in this study. [ABSTRACT FROM AUTHOR]

This study compared the impact of methylphenidate on patients with Attention-deficit Hyperactivity Disorder (ADHD) with and without aggressive/noncompliant features in an oddball test consisting of a randomly ordered series of loud (frequent) tones, soft (rare) tones, bright (frequent) lights, and dim (rare) lights. In alternate conditions, subjects were required to respond to either the rare tones or the rare lights. These tasks were administered in a drug-free baseline session and after a counterbalanced treatment of 14 days each of methylphenidate (0.3 mg/Kg b.i.d.) and placebo (lactose b.i.d.). In comparison with placebo, methylphenidate resulted in greater accuracy and speed of reactions to targets of both modalities. The amplitude of N1 to auditory nontargets was larger when the target was a rare tone as opposed to a rare light, and this attention-related effect was increased by methylphenidate. The same differential amplitude enhancement by stimulant treatment was found for an early area measure of difference ERPs. In contrast, for N1 to visual nontargets the effect of selective attention (larger amplitude when the target was a rare light vs. a rare tone) was not significant and was not affected by stimulant medication. All these findings were comparable for the three ADHD subgroups, a result attesting to the generality of stimulant effects on information processing. [ABSTRACT FROM AUTHOR]

This study investigated the effects of methylphenidate in a memory scanning task with two Levels of high cognitive load (memory set sizes 2 and 4 presented in displays of size 4) and two response requirements (simple mapping or rotation). Twenty young adults were tested under placebo and methylphenidate (0.3 mg/Kg) in a double-blind protocol. As expected, memory load increased misses, false alarms, confusions, and failures to respond by the deadline. In turn, the rotation requirement increased confusions and nonresponses. Reaction time (RT) was slowed by both factors. P3b latency also was increased by memory load and, to some extent, by the rotation requirement. These results are consistent with the proposition that P3b Latency reflects largely evaluation, rather than response processes. Misses and reaction time were decreased in response to targets presented in the center vs. the periphery of the display. Confusions, however, showed the opposite trend. The display position did not affect P3b latency. These results can be explained by assuming that the subject was focusing on the center of the display and that accuracy diminished when stimuli were presented toward the periphery of the display. The stimulant challenge speeded up reaction times overall and specifically reduced the slowing effect of rotation. However, P3b latency was not affected by methylphenidate, so that the speeding of reaction time by the stimulant can be attributed to post-evaluation processes. [ABSTRACT FROM AUTHOR]

Evoked potentials during the X and B-X versions of the Continuous Performance Test (CPT) were evaluated in 29 hyperactive children after ingestion of placebo or methylphenidate (0.3 mg/Kg). Twenty-one age matched normal children were also assessed twice but without any drugs. In both tests, placebo-treated hyperactives made more omission and commission errors and displayed smaller late positive components (LPC) of the evoked response to salient experimental cues. Methylphenidate ameliorated hyperactives' performance in both tasks and enlarged their LPCs in CPT-X. Several of these drug effects and diagnostic differences were absent for older hyperactive subjects, probably because some of the procedures were too easy for them. For younger patients the present tasks were sufficiently challenging, and the results reflect normalization of their deficits in sustained attention. [ABSTRACT FROM AUTHOR]

Eighteen hyperactive clinical responders to methylphenidate were taken off medication and tested in two sessions during which they received an acute dose of methylphenidate and placebo in counterbalanced order. Seventeen normal boys of comparable age were tested without drugs. For both samples, evoked potentials were recorded during a Continuous Performance Test. Normal children made fewer errors of commission and omission and displayed faster reaction times than hyperactives tested under placebo. In addition, under active attention, the late positive component (LPC) of placebo-treated hyperactive boys' evoked responses exhibited smaller amplitude than normal controls'. Methylphenidate increased the amplitude of hyperactive patients' LPC and generally ameliorated their performance, especially commission errors and reaction times. The results confirmed previous findings of attentional disturbance in hyperactivity and normalization by methylphenidate of these patients' performance and electrophysiological activity during sustained attention. [ABSTRACT FROM AUTHOR]

Twenty-two normal young men received a counterbalanced and double blind administration of 20 mg methylphenidate and placebo. Two tasks were administered in counterbalanced order: an uninterrupted 45-min vigilance test and a paired-associates learning test. As previously reported, under placebo, accuracy and speed decreased monotonically over the course of the vigil. This degradation of performance was significantly reduced by the stimulant drug. Event-related potentials (ERPs) were derived for correctly detected targets and nontargets. The most salient pharmacologic effects involved a late positive wave (P464) identified as P3b. Methylphenidate reversed or reduced the decrease in amplitude and increase in latency of P464 present over phases of the placebo session. The results suggest that the stimulant-induced improvement in performance may be mediated by enhancement of evaluation processes. In the paired-associates test there were no pharmacologic effects. Instead there was an unexpected, pronounced improvement in learning in the second session, irrespective of the substance administered. However, the ERP evoked by the "stimulus" cue of each pair was systematically related to the achievement of learning criteria. A late positive wave identified as P3b (P555) increased significantly in amplitude following the attainment of learning. There were no amplitude changes among ERPs evoked in the early post-criterion, late post-criterion, or overlearning "phases.'' Nor were there amplitude changes between early and late pre-criterion categories. Thus, ERP amplitude displayed a binary association with the achievement of learning. [ABSTRACT FROM AUTHOR]