The specificity of the effects of stimulant medication on classroom learning-related measures of cognitive processing for Attention Deficit Disorder children

There appear to be beneficial effects of stimulant medication on daily classroom measures of cognitive functioning for Attention Deficit Disorder (ADD) children, but the specificity and origin of such effects is unclear. Consistent with previous results, 0.3 mg/kg methylphenidate improved ADD children's performance on a classroom reading comprehension measure. Using the Posner letting-matching task and four additional measures of phonological processing, we attempted to isolate the effects of methylphenidate to parameter estimates of (a) selective attention, (b) the basic cognitive process of retrieving name codes from permanent memory, and (c) a constant term that represented nonspecific aspects of information processing. Responses to the letter-matching stimuli were faster and more accurate with medication compared to placebo. The improvement in performance was isolated to the parameter estimate that reflected nonspecific aspects of information processing. A lack of medication effect on the other measures of phonological processing supported the Posner task findings in indicating that methylphenidate appears to exert beneficial effects on academic processing through general rather than specific aspects of information processing.     

Methylphenidate and cognitive therapy with add children: A methodological reconsideration

The present doubleblind study examined the effects of methylphenidate, cognitive therapy, and their combination in attention deficitdisordered (ADD) children. Four treatment groups were compared on measures of attentional deployment and cognitive style, tests of academic achievement, and behavioral rating scales. In contrast to a previous study conducted in this laboratory, children in this study were not receiving medication during posttesting. Results were interpreted to suggest that measurable effects of stimulant medication dissipate rapidly upon discontinuation of pharmacotherapy. The combination of methylphenidate and cognitive therapy was not found to be any more efficacious than either of the treatments studied alone. Discussion suggests that medication status at follow-up is an essential feature of research design.This research was supported in full by U.S. Public Health Service Grant No. MH 37-628 from the National Institute of Mental Health, Psychopharmacology Branch, and by Biomedical Research Award No. RR 0715807 from the National Institutes of Health, each awarded to R. T. Brown. Placebo and methylphenidate were supplied by CIBA-GEIGY, Summit, New Jersey. The authors are grateful to Dr. Rute Medenis and the entire staff at the University of Illinois Pediatrics Clinic for their valuable assistance and kind support throughout the project. The authors would also like to thank Avery L. Spunt, R.Ph., College of Pharmacy, University of Illinois, for his assistance in packaging the medication and monitoring compliance; Arthur I. Neyhus, Ph.D., Coordinator of Child Study Facility, University of Illinois at Chicago, for his assistance in evaluation; and J. Scott Allen, Jimmy Bruce, Robert Miller, Michael Mazius, and Steven Orenczuk, for their assistance in training of the children.The contributions of these authors are equal.     

The effects of background illumination and stimulant medication on smooth pursuit eye movements of hyperactive children

Problems with visual information processing have been reported in children with the diagnosis of attention deficit disorder with hyperactivity (ADD H), and deficits in oculomotor control have been posited as an important factor in this phenomenon. To assess aspects of oculomotor performance, smooth pursuit eye movements (PEMs) were recorded electrooculographically in 20 ADD H and 20 age-matched control children and computer-analyzed for discrete (velocity arrests) and global (root mean square error) disruptions. The effects of stimulant medication (methylphenidate), together with manipulations designed to influence behavioral (attention) and physiological (cerebellar) processes involved in PEM performance, were examined. The tracking patterns of nonmedicated ADD H children contained significantly more discrete aberrations on baseline conditions. Although no single experimental manipulation significantly improved tracking performance in ADD H children, combining all experimental conditions did normalize PEMs in these subjects. Slight improvements in PEM performance in association with medication correlated positively with does of madication of with medication-related improvments of behavior. In light of these data, arguments are presented in supported of (a) hyporousal as a contributing factor underlying oculomotor difficulties in ADD H children and (b) subcortical involbment in PEM dysfunction.This research was funded in part by grants from The Hospital for Sick Children Foundation and the Ontario Mental Health Foundation (RTP). The authors thank Susan Anthony, Dr. Pamela M. Cooper, Stella Cowley, Dr. Kathy Margittai, and Ralph Nevins for technical assistance, Martin Gillett for computer programming, Dr. Phil Firestone and the staff of the University of Ottawa Child Study Centre, and Dr. B. Lena of the Family and Child Unit, Ottawa General Hospital, for subject referral.     

Acute Stimulant Treatment and Reinforcement Increase the Speed of Information Accumulation in Children with ADHD

The current studies utilized drift diffusion modeling (DDM) to examine how reinforcement and stimulant medication affect cognitive task performance in children with ADHD. In Study 1, children with (n = 25; 88 % male) and without ADHD (n = 33; 82 % male) completed a 2-choice discrimination task at baseline (100 trials) and again a week later under alternating reinforcement and no-reinforcement contingencies (400 trials total). In Study 2, participants with ADHD (n = 29; 72 % male) completed a double-blind, placebo-controlled trial of 0.3 and 0.6 mg/kg methylphenidate and completed the same task utilized in Study 1 at baseline (100 trials). Children with ADHD accumulated information at a much slower rate than controls, as evidenced by a lower drift rate. Groups were similar in nondecision time and boundary separation. Both reinforcement and stimulant medication markedly improved drift rate in children with ADHD (ds = 0.70 and 0.95 for reinforcement and methylphenidate, respectively); both treatments also reduced boundary separation (ds = 0.70 and 0.39). Reinforcement, which emphasized speeded accuracy, reduced nondecision time (d = 0.37), whereas stimulant medication increased nondecision time (d = 0.38). These studies provide initial evidence that frontline treatments for ADHD primarily impact cognitive performance in youth with ADHD by improving the speed/efficiency of information accumulation. Treatment effects on other DDM parameters may vary between treatments or interact with task parameters (number of trials, task difficulty). DDM, in conjunction with other approaches, may be helpful in clarifying the specific cognitive processes that are disrupted in ADHD, as well as the basic mechanisms that underlie the efficacy of ADHD treatments.     

未意识到错误影响错误后调整的电生理证据

现有研究一致认为意识到错误可引起错误后调整, 但是未意识到错误能否促使个体进行错误后调整尚存争议。本实验采用基于go/no-go范式的错误意识任务考察上述问题, 并根据被试对自己按键反应正误主观报告将no-go错误反应分为意识到错误和未意识到错误。行为结果发现, 意识到错误和未意识到错误后正确率均显著高于正确击中试次(正确go试次)后正确率; 但是, 意识到错误后试次反应时显著快于正确击中后反应时, 未意识到错误后反应时显著慢于正确击中后反应时。该结果表明两类错误均优化了错误后行为表现, 但是意识到错误后被试调整速度加快, 未意识到错误后被试调整速度减慢。进而, 时频分析发现意识到错误相较于未意识到错误诱发显著更强的alpha波能量。并且, 前者在错误意识主观报告前已诱发alpha波, 后者在错误意识主观报告反应后诱发alpha波。该结果表明意识到错误一直处于持续的注意监控中, 而未意识到错误是任务引起的暂时注意控制。因此, 本实验说明错误意识影响错误后调整, 意识到错误可能采用类似主动性控制的策略调节错误后行为, 而未意识到错误可能采用类似反应性控制的策略调节错误后行为。     

Effects of methylphenidate on kinematic aspects of handwriting in hyperactive boys

Poor handwriting in hyperactive children often contributes to academic failure. Beneficial effects of methylphenidate on the quality of handwriting have been shown. Using a digitizing tablet, the handwriting of 21 hyperactive boys was examined both during methylphenidate treatment and following withdrawal of the drug. Half of the hyperactive boys were tested first on methylphenidate and then following withdrawal of the drug and the remaining hyperactive boys were examined in the reverse order. Twenty-one control boys underwent the same examination. Velocity and acceleration of handwriting movements were measured. Furthermore, every writing specimen was independently rated by four examiners regarding the quality of handwriting. Following withdrawal of the drug, the quality of handwriting specimens of hyperactive boys was poorer than during treatment with methylphenidate. Statistical comparison of writing movements of hyperactive boys on and off methylphenidate revealed that the medication resulted in a deterioration in handwriting fluency. The results showed that following withdrawal of medication, hyperactive children did not differ from control boys in handwriting movements. The improvement in hyperactive behavior through methylphenidate was associated with increased legibility and greater accuracy of handwriting. The intention to write neatly may interfere with the fluent writing process.     

Preliminary evidence for reduced posterror reaction time slowing in hyperactive/inattentive preschool children

Background: Attention deficit/hyperactivity disorder (ADHD) has been associated with deficits in self-regulatory cognitive processes, some of which are thought to lie at the heart of the disorder. Slowing of reaction times (RTs) for correct responses following errors made during decision tasks has been interpreted as an indication of intact self-regulatory functioning and has been shown to be attenuated in school-aged children with ADHD. This study attempted to examine whether ADHD symptoms are associated with an early-emerging deficit in posterror slowing. Method: A computerized two-choice RT task was administered to an ethnically diverse sample of preschool-aged children classified as either “control” (n = 120) or “hyperactive/inattentive” (HI; n = 148) using parent- and teacher-rated ADHD symptoms. Analyses were conducted to determine whether HI preschoolers exhibit a deficit in this self-regulatory ability. Results: HI children exhibited reduced posterror slowing relative to controls on the trials selected for analysis. Supplementary analyses indicated that this may have been due to a reduced proportion of trials following errors on which HI children slowed rather than due to a reduction in the absolute magnitude of slowing on all trials following errors. Conclusions: High levels of ADHD symptoms in preschoolers may be associated with a deficit in error processing as indicated by posterror slowing. The results of supplementary analyses suggest that this deficit is perhaps more a result of failures to perceive errors than of difficulties with executive control.     

Consciousness is slower than you think

In easy serial choice reaction time tasks (CRT tasks) young adults can very rapidly "correct" nearly all their errors by making the responses that they should have made (error-correcting responses). They are much less accurate at signalling their errors by making the same, deliberate, response to each (error-signalling responses), and they poorly remember errors that they have not signalled or corrected. When instructed to ignore errors they nevertheless involuntarily register them because the response immediately following them (responses following unacknowledged errors) are unusually slow, and they sometimes make involuntary error correction responses. Errors that are neither signalled nor remembered are registered at some level because responses following unacknowledged errors are slowed. Old age does not impair the accuracy of error correction or reduce the proportion of errors that are acknowledged because they are followed by unusually slow responses, but it does reduce the accuracy of error signalling and of recall of errors. Groups of 40 young adults (mean age 20.1 years, SD 1.1) and 40 older adults (mean 71.2 years, SD 5.1) signalled and recalled their errors increasingly accurately as intervals between each response and the next signal were increased from 150 ms to 1000 ms. Error signalling and recall improved as response-signal interval (RSI) durations increased, reaching asymptote at RSIs of 800 ms for the young and 1000 ms for the older adults. Thus processes necessary for conscious and deliberate choice or error-signalling responses and for subsequent recall of errors require more than 150 ms to complete, are slowed by old age, and may be interrupted by onset of new signals occurring earlier than 800 to 1000 ms after completion of an incorrect response.     

DIFFERENTIAL REINFORCEMENT OF CORRECT RESPONSES TO PROBES AND PROMPTS IN PICTURE-NAME TRAINING WITH SEVERELY RETARDED CHILDREN

A systematic sequence of prompt and probe trials was used to teach picture names to three severely retarded children. On prompt trials the experimenter presented a picture and said the picture name for the child to imitate; on probe trials the experimenter did not name the picture. A procedure whereby correct responses to prompts and probes were nondifferentially reinforced was compared with procedures whereby correct responses to prompts and probes were differentially reinforced according to separate and independent schedules of primary reinforcement. In Phase 1, correct responses to prompts and probes were reinforced nondifferentially on a fixed ratio (FR) 6 or 8 schedule; in Phase 2, correct responses to prompts were reinforced on the FR schedule and correct responses to probes were reinforced on an FR schedule of the same value; in Phase 3, correct responses to prompts were reinforced on the FR schedule and correct responses to probes were reinforced on a continuous reinforcement (CRF; every correct response reinforced) schedule; in Phase 4, correct responses to prompts were reinforced on a CRF schedule and correct responses to probes were reinforced on the FR schedule; in Phase 5, a reversal to the conditions of Phase 3 was conducted. For all three children, the FR schedule for correct responses to prompts combined with the CRF schedule for correct responses to probes (Phases 3 and 5) generated the highest number of correct responses to probes, the highest accuracy (correct responses relative to correct responses plus errors) on probe trials, and the highest rate of learning to name pictures.     

Modeling Response Times for Two-Choice Decisions

The diffusion model for two-choice real-time decisions is applied to four psychophysical tasks. The model reveals how stimulus information guides decisions and shows how the information is processed through time to yield sometimes correct and sometimes incorrect decisions. Rapid two-choice decisions yield multiple empirical measures: response times for correct and error responses, the probabilities of correct and error responses, and a variety of interactions between accuracy and response time that depend on instructions and task difficulty. The diffusion model can explain all these aspects of the data for the four experiments we present. The model correctly accounts for error response times, something previous models have failed to do. Variability within the decision process explains how errors are made, and variability across trials correctly predicts when errors are faster than correct responses and when they are slower.     

Treatment Sensitivity of a Brief Rating Scale for Attention-Deficit Hyperactivity Disorder (ADHD) Symptoms

This study examined the treatment sensitivity of the ADHD Questionnaire (ADHD-Q), which is a brief rating scale for measuring symptoms of inattention, hyperactivity, and impulsivity in children. Parent, teacher, and child self-report data of the ADHD-Q were obtained for 17 clinically referred children with ADHD on the three occasions: (1) during the regular intake assessment, (2) just before the start of the stimulant medication (i.e., methylphenidate) intervention, and (3) four weeks after the start of the medication intervention. Results showed that ADHD-Q scores remained fairly stable in the period prior to the intervention, but then showed a substantial decline after the stimulant medication had been administered. Clearly, this finding supports the treatment sensitivity of the ADHD-Q.     

Committing memory errors with high confidence: older adults do but children don't

We investigated lifespan differences of confidence calibration in episodic memory, particularly the susceptibility to high-confidence errors within samples of children, teenagers, younger adults, and older adults. Using an associative recognition memory paradigm, we drew a direct link between older adults' associative deficit and high-confidence errors. We predicted that only older adults would show high-confidence error even though their memory performance was at a similar level to that of children. Participants of all ages showed higher confidence following correct responses compared to incorrect responses, demonstrating the ability to calibrate subjective confidence in relation to memory accuracy. However, older adults were disproportionately more likely to indicate high confidence following erroneously remembered word pairs than participants of the other three age groups. Results are discussed in relation to the misrecollection account of high-confidence errors and ageing-related decline in hippocampus-dependent episodic memory functions.     

Stimulant Treatment Reduces Lapses in Attention among Children with ADHD: The Effects of Methylphenidate on Intra-Individual Response Time Distributions

Recent research has suggested that intra-individual variability in reaction time (RT) distributions of children with ADHD is characterized by a particularly large rightward skew that may reflect lapses in attention. The purpose of the study was to provide the first randomized, placebo-controlled test of the effects of the stimulant methylphenidate (MPH) on this tail and other RT distribution characteristics. Participants were 49 9- to 12-year-old children with ADHD. Children participated in a 3-day double-blind, placebo-controlled medication assessment during which they received long-acting MPH (Concerta®), with the nearest equivalents of 0.3 and 0.6 mg/kg t.i.d. immediate-release MPH. Children completed a simple two-choice speeded discrimination task on and off of medication. Mode RT and deviation from the mode were used to examine the peak and skew, respectively, of RT distributions. MPH significantly reduced the peak and skew of RT distributions. Importantly, the two medication effects were uncorrelated suggesting that MPH works to improve both the speed and variability in responding. The improvement in variability with stimulant treatment is interpreted as a reduction in lapses in attention. This, in turn, may reflect stimulant enhancement of self-regulatory processes theorized to be at the core of ADHD.     

Effects of methylphenidate (Ritalin) on selective attention in hyperactive children

This study investigated the effect of methylphenidate (Ritalin) on the selective attention of hyperactive children designated as favorable or adverse responders to stimulant medication. Using a type II incidental learning paradigm, it was found that children in the drug condition recalled more central and less incidental stimuli than those children in the placebo condition. While no differential effects on recall were found for responder type, methylphenidate did affect the spontaneous overt labeling of central stimuli by the favorable responder group. Results were interpreted in terms of the role of methylphenidate in narrowing the focus of attention. Implications for the classification of hyperactive children as favorable and adverse responders were also discussed.This paper is based on a master's thesis completed by the first author in the Department of Psychology, University of Guelph, under the supervision of the second author. The authors wish to thank J. Thomas Dalby for his assistance in the conducting of this experiment.     

The acquisition of behavioral chains

The present investigation was designed to study some conditions which facilitate the acquisition of behavioral chains by young children. Three experiments were performed. In Expt I subjects were required to respond overtly to the internal components of the chain. In Expt II an aversive contingency was imposed following errors. In Expt III instructions were added at the beginning of training. The results supported the following conclusions: (a) Requiring subjects to mark and name the correct stimuli on each trial increased the accuracy of performance; (b) introducing time-out contingent on incorrect responses depressed the error rate; and (c) adding instructions concerning a pending change in the experimental task resulted in a lower error rate following withdrawal of the instructional stimuli.     

Fundamental Movement Skills and Children with Attention-Deficit Hyperactivity Disorder: Peer Comparisons and Stimulant Effects

The purpose of this study was to compare the fundamental movement skills of 22 children with attention-deficit hyperactivity disorder (ADHD), from 6 to 12 years of age, to gender- and age-matched peers without ADHD and assess the effects of stimulant medication on the movement skill performance of the children with ADHD. Repeated measures analyses revealed significant skill differences between children with and without ADHD (p ≤ 0.001). Results from the stimulant medication trials indicated no significant effect of medication on the movement skill patterns of children with ADHD. It is concluded that children with ADHD may be at risk for developmental delays in movement skill performance. Potential factors underlying the movement skill difficulties are discussed, with suggestions for future research.     

Anxiety and expectancy violations: Neural response to false feedback is exaggerated in worriers

This study investigated how individual differences in anxiety modulate the neural response to errors and performance feedback. The design included false feedback on some trials in order to test the hypothesis that anxious people show stronger neural reactions to feedback that is worse than expected. Participants completed a trial-and-error learning task that required learning the correct key to press in response to face images. EEG was recorded during the task, and the response-locked error-related negativity (ERN) and feedback-locked ERN were computed to measure neural responses to error commission and feedback. As expected, errors produced a response-locked ERN and false feedback produced a feedback-locked ERN in the group as a whole. High levels of trait worry predicted a disproportionately larger ERN following false feedback, but did not predict the magnitude of the response-locked ERN following errors. These results imply that worry-prone people react more strongly to violations of expectations, rather than to errors themselves.     

Cognitive demands of error processing

This study used a dual-task methodology to assess attention demands associated with error processing during an anticipation-timing task. A difference was predicted in attention demands during feedback on trials with correct responses and errors. This was addressed by requiring participants to respond to a probe reaction-time stimulus after augmented feedback presentation. 16 participants (8 men, 8 women) completed two phases, the reaction time task only and the anticipation-timing task with the probe RT task. False feedback indicating error and a financial reward manipulation were used to increase relevance of errors. Data supported the hypothesis that error processing is associated with higher cognitive demands than processing feedback denoting a correct response. Individuals responded with quicker probe reaction times during presentation of feedback on correct trials than on error trials. These results are discussed with respect to the cognitive processes which might occur during error processing and their role in motor learning.     

Frontal lobe functions in attention deficit disorder with and without hyperactivity: A review and research report

We review 22 neuropsychological studies of frontal lobe functions in children with attention deficit disorder with and without hyperactivity (ADD/+H,ADD/-H). Some measures presumed to assess frontal lobe dysfunctions were not reliably sensitive to the deficits occurring in either form of ADD. Tests of response inhibition more reliably distinguished ADD/+H from normal children. Where impairments were found on other tests between ADD and normal subjects, they were highly inconsistent across studies and seemed strongly related to age of the subjects and possibly to the version of the test employed. Other methodological differences across studies further contributed to the discrepant reports. The co-morbidity of other disorders, such as learning disabilities (LD) and conduct problems, with ADD may be an additional confounding factor in some, though not all, of these studies. In a separate study, children with ADD/+H (n=12) were then compared on frontal lobe tests to three other groups: ADD/-H (n=12), LD but no ADD (n=11),and normal children (n=12) statistically covarying for differences in conduct problems across groups. Most measures did not distinguish among these groups. Both ADD groups made more omission errors on a Continuous Performance Test (CPT) than the normal group. All three clinical groups performed more poorly on the word and interference portions of the Stroop Test. Thus, while both types of ADD share some apparent similarities in deficits on a few frontal lobe tests in this study, the totality of existing findings suggests an additional problem with perceptual-motor speed and processing in the ADD/-H group.This research was supported by NIMH grant MH41464 and by funds from the Department of Psychiatry, University of Massachusetts Medical Center. The authors are grateful to Judy Tessier and Ellen Mintz-Lennick for their assistance with some of the data collection and scoring. The comments of Virginia Douglas on an earlier draft of this paper are greatly appreciated.