Effects of two doses of methylphenidate on cross-situational and borderline hyperactive children's evoked potentials

Sensory processing and P300 event-related potential correlates of stimulant response in children with attention-deficit/hyperactivity disorder: A critical review

Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder associated with considerable impairment in psychiatric and functional domains. Although stimulant medication can reduce core symptoms of inattention, hyperactivity, and impulsivity, a subgroup of patients does not respond to this intervention. A precision medicine approach has been proposed, whereby biomarkers are used to identify an effective treatment approach for a given individual. This review synthesizes the existing literature on event-related potential (ERP) correlates of stimulant response in children diagnosed with ADHD, with the goal of evaluating the potential for ERP to inform precision medicine care in this population. Forty-three articles were examined and results tentatively suggest that stimulant medications normalize the amplitude of the P300 component, and this is also associated with behavioral improvement. In contrast, results generally indicate that stimulants do not significantly alter early processing components, although there are some exceptions to this finding. Implications for research, theory, and clinical work are considered and concrete recommendations for future directions are provided. While recognizing limitations of existing literature (e.g., homogenous samples, variable methodologies), we conclude that ERP methods represent a promising approach for precision medicine care of patients with ADHD.

Neuronal Correlates of Cognitive Control Are Altered in Women With Endometriosis and Chronic Pelvic Pain

Endometriosis is a debilitating women's health condition and is the most common cause of chronic pelvic pain. Impaired cognitive control is common in chronic pain conditions, however, it has not yet been investigated in endometriosis. The aim of this study was to explore the neuronal correlates of cognitive control in women with endometriosis. Using a cross-sectional study design with data collected at a single time-point, event-related potentials were elicited during a cued continuous performance test from 20 women with endometriosis (mean age = 28.5 ± 5.2 years) and 20 age- and gender-matched controls (mean age = 28.5 ± 5.2 years). Event-related potential components were extracted and P3 component amplitudes were derived with temporal principal components analysis. Behavioral and ERP outcomes were compared between groups and subjective pain severity was correlated with ERP component amplitudes. No significant behavioral differences were seen in task performance between the groups (all p > 0.094). Target P3b (all p < 0.034) and SW (all p < 0.040), and non-target early P3a (eP3a; all p < 0.023) and late P3a (lP3a; all p < 0.035) amplitudes were smaller for the endometriosis compared to the healthy control group. Lower non-target eP3a (p < 0.001), lP3a (p = 0.013), and SW (p = 0.019) amplitudes were correlated with higher pain severity scores. Findings suggest that endometriosis-associated chronic pelvic pain is linked to alterations in stimulus-response processing and inhibitory control networks, but not impaired behavioral performance, due to compensatory neuroplastic changes in overlapping cognitive control and pain networks.

Dopaminergic modulation of default mode network brain functional connectivity in attention deficit hyperactivity disorder

INTRODUCTION

Recent evidence suggests that attention deficit hyperactivity disorder (ADHD) is associated with a range of brain functional connectivity abnormalities, with one of the most prominent being reduced inhibition of the default mode network (DMN) while performing a cognitive task. In this study, we examine the effects of a methylphenidate dose on brain functional connectivity in boys diagnosed with ADHD while they performed a cognitive task.

METHOD

Brain functional connectivity was estimated using steady-state visual evoked potential partial coherence before and 90 min after the administration of a methylphenidate dose to 42 stimulant drug-naïve boys newly diagnosed with ADHD while they performed the A-X version of the continuous performance task (CPT A-X).

RESULTS

Methylphenidate robustly reversed the transient functional connectivity increase in the A-X interval seen premedication to a postmedication decrease during this interval. In addition, methylphenidate-induced reductions in individual reaction time were correlated with corresponding reductions in functional connectivity.

CONCLUSION

These findings suggest that methylphenidate suppresses the increased functional connectivity observed in ADHD and that such suppression is associated with improved performance. Our findings support the suggestion that the increased functional connectivity we have observed in ADHD is associated with abnormal DMN activity. In addition, we comment on the significance of specific frequency channels mediating top-down communication within the cortex and the extent to which our findings are selectively sensitive to top-down intracortical communication.

Attention-Deficit Hyperactivity Disorder

Attention-deficit hyperactivity disorder (ADHD) is the most common of the childhood psychiatric disorders, with a prevalence rate of up to 20%, and is probably genetically transmitted. ADHD is characterized by impulsive behavior, hyperactivity, and decreased attention span. It is often extremely disruptive to the afflicted individuals social interactions and school performance. Therapeutic approaches to ADHD should be multimodal, including medications, family, and educational therapies. The pathophysiology of ADHD is not yet fully understood. Catecholoamines are believed to play a significant role with serotonin in an adjunctive role. Pathophysiological theories are supported by useful drug therapies that are known to affect dopamine and norepinephrine metabolism. Stimulants remain the drugs of choice, with methylphenidate most commonly used. Dextroamphetamine and pemoline are also effective. The rational use of these drugs is discussed. Antidepressants are second-line drug therapies; their usefulness is most apparent in patients who have high levels of anxiety and/or depression. Other potentially useful medications, including clonidine and the antipsychotics, are discussed. Adult populations can also express ADHD; treatment is similar to that used in children. Overall, ADHD is an important illness with significant morbidity. Pharmacotherapy is highly effective for its treatment and forms the cornerstone of therapy. This review of ADHD seeks to promote a greater understanding of this disorder and its appropriate drug therapy.

The utility of rat models of impulsivity in developing pharmacotherapies for impulse control disorders

High levels of impulsive behaviours are a clinically significant symptom in a range of psychiatric disorders, such as attention deficit hyperactivity disorder, bipolar disorder, personality disorders, pathological gambling and substance abuse. Although often measured using questionnaire assessments, levels of different types of impulsivity can also be determined using behavioural tests. Rodent analogues of these paradigms have been developed, and similar neural circuitry has been implicated in their performance in both humans and rats. In the current review, the methodology underlying the measurement of different aspects of impulsive action and choice are considered from the viewpoint of drug development, with a focus on the continuous performance task (CPT), stop-signal task (SST), go/no-go and delay-discounting paradigms. Current issues impeding translation between animal and human studies are identified, and comparisons drawn between the acute effects of dopaminergic, noradrenergic and serotonergic compounds across species. Although the field could benefit from a more systematic determination of different pharmacological agents across paradigms, there are signs of strong concordance between the animal and human data. However, the type of impulsivity measured appears to play a significant role, with the SST and delay discounting providing more consistent effects for dopaminergic drugs, while the CPT and SST show better predictive validity so far for serotonergic and noradrenergic compounds. Based on the available data, it would appear that these impulsivity models could be used more widely to identify potential pharmacotherapies for impulse control disorders. Novel targets within the glutamatergic and serotonergic system are also suggested.

EVENT-RELATED POTENTIAL STUDY OF ATTENTION REGULATION DURING ILLUSORY FIGURE CATEGORIZATION TASK IN ADHD, AUTISM SPECTRUM DISORDER, AND TYPICAL CHILDREN

Autism spectrum disorders (ASD) and attention deficit/hyperactivity disorder (ADHD) are very common developmental disorders which share some similar symptoms of social, emotional, and attentional deficits. This study is aimed to help understand the differences and similarities of these deficits using analysis of dense-array event-related potentials (ERP) during an illusory figure recognition task. Although ADHD and ASD seem very distinct, they have been shown to share some similarities in their symptoms. Our hypothesis was that children with ASD will show less pronounced differences in ERP responses to target and non-target stimuli as compared to typical children, and to a lesser extent, ADHD. Participants were children with ASD (N=16), ADHD (N=16), and controls (N=16). EEG was collected using a 128 channel EEG system. The task involved the recognition of a specific illusory shape, in this case a square or triangle, created by three or four inducer disks. There were no between group differences in reaction time (RT) to target stimuli, but both ASD and ADHD committed more errors, specifically the ASD group had statistically higher commission error rate than controls. Post-error RT in ASD group was exhibited in a post-error speeding rather than corrective RT slowing typical for the controls. The ASD group also demonstrated an attenuated error-related negativity (ERN) as compared to ADHD and controls. The fronto-central P200, N200, and P300 were enhanced and less differentiated in response to target and non-target figures in the ASD group. The same ERP components were marked by more prolonged latencies in the ADHD group as compared to both ASD and typical controls. The findings are interpreted according to the "minicolumnar" hypothesis proposing existence of neuropathological differences in ASD and ADHD, specifically minicolumnar number/width morphometry spectrum differences. In autism, a model of local hyperconnectivity and long-range hypoconnectivity explains many of the behavioral and cognitive deficits present in the condition, while the inverse arrangement of local hypoconnectivity and long-range hyperconnectivity in ADHD explains some deficits typical for this disorder. The current ERP study supports the proposed suggestion that some between group differences could be manifested in the frontal ERP indices of executive functions during performance on an illusory figure categorization task.

Methylphenidate effect in children with ADHD can be measured by an ecologically valid continuous performance test embedded in virtual reality

BACKGROUND

Continuous performance tasks (CPTs) embedded in a virtual reality (VR) classroom environment have been shown to be a sensitive and user-friendly assessment tool to detect cognitive deficits related to attention-deficit/hyperactivity disorder (ADHD). The aim of the current study was to compare the performance of children with ADHD on a VR-CPT while on and off treatment with methylphenidate (MPH) and to compare the VR-CPT to a currently used CPT, Test of Variables of Attention (TOVA).

METHODS

Twenty-seven children with ADHD underwent the VR-CPT, the same CPT without VR (no VR-CPT), and the TOVA, 1 hour after the ingestion of either placebo or 0.3 mg/kg MPH, in a double-blind, placebo-controlled, crossover design. Immediately following CPT, subjects described their subjective experiences on the Short Feedback Questionnaire.

RESULTS

MPH reduced omission errors to a greater extent on the VR-CPT compared to the no VR-CPT and the TOVA, and decreased other CPT measures on all types of CPT to a similar degree. Children rated the VR-CPT as more enjoyable compared to the other types of CPT.

CONCLUSIONS

It is concluded that the VR-CPT is a sensitive and user-friendly assessment tool in measuring the response to MPH in children with ADHD.

Event-related potentials in clinical research: guidelines for eliciting, recording, and quantifying mismatch negativity, P300, and N400

This paper describes recommended methods for the use of event-related brain potentials (ERPs) in clinical research and reviews applications to a variety of psychiatric and neurological disorders. Techniques are presented for eliciting, recording, and quantifying three major cognitive components with confirmed clinical utility: mismatch negativity (MMN), P300, and N400. Also highlighted are applications of each of the components as methods of investigating central nervous system pathology. The guidelines are intended to assist investigators who use ERPs in clinical research, in an effort to provide clear and concise recommendations and thereby to standardize methodology and facilitate comparability of data across laboratories.

Methylphenidate effects in attention deficit/hyperactivity disorder: electrodermal and ERP measures during a continuous performance task

RATIONALE

Previous research investigating the effects of stimulants, such as methylphenidate (MPH), on children with attention deficit/hyperactivity disorder (AD/HD) has rarely included autonomic measures of arousal.

OBJECTIVE

Our aim was to clarify the effects of MPH on central and autonomic measures in AD/HD children during a continuous performance task (CPT) using a naturalistic open-label study.

METHOD

Thirty-six boys (18 AD/HD and 18 control) participated in a CPT over two trial periods, allowing a more valid estimate of the effects of medication, rather than assuming that retesting per se has no substantial impact. MPH was administered to the AD/HD group 1 h prior to the second trial. Errors and reaction time (RT) were recorded as measures of performance, electrodermal activity as an autonomic nervous system measure and event-related potentials (ERPs) as an index of central nervous system activity.

RESULTS

AD/HD children made more errors than controls in the first session, but no group differences were found after medication. No significant differences were observed for RT. Skin conductance level was found to be lower in AD/HD children than controls, but this difference was also ameliorated after medication. Conversely, mean skin conductance response to target stimuli was found not to differ between groups during the initial test phase but became significantly different in phase 2. ERP data showed topographic differences between groups in N1, P2, N2 and P3 at the initial test phase, which were reduced at the second test.

CONCLUSION

Stimulant medication ameliorated some of the dysfunctions in AD/HD children, which are reflected in behavioural and ERP measures. These results, in combination with general differences in electrodermal activity, support a hypo-arousal model of AD/HD, which can explain the action of MPH in these children.

Continuous performance test performance in a normative epidemiological sample

A 14-min continuous performance test (CPT) requiring a high rate of responding was administered to a probability-weighted random sample of 816 9-17-year-old children drawn from a population of 17,117 children in an ongoing epidemiological and longitudinal study in Western North Carolina. Systematic main effects of improved performance with older age were found in this age range for all variables, including reaction time (RT), RT standard error, errors of omission, errors of commission, and signal detection parameters (d' and beta). Significant gender main effects included more impulsive errors, less variability, and faster RT by males, with no interactions between age and gender. There were no main effects of ethnicity or interactions of ethnicity with age and/or gender. Large main effects of interstimulus interval (ISI; 1, 2, or 4-s intervals) and time block were present for most CPT performance measures. The normative data from the CPT should provide a useful framework for interpreting similar data in future studies of child and adolescent psychopathology.

CNS recovery from cocaine, cocaine and alcohol, or opioid dependence: a P300 study

OBJECTIVES

The goal of the present study was to evaluate the relative effects of cocaine, cocaine and alcohol, or opioid dependence on P300 event-related potentials (ERPs). In addition, the effects of selected premorbid and comorbid factors were examined.

METHODS

P300 ERPs were recorded from 72 residential treatment program patients, characterized by a history of either cocaine (n=25), or cocaine and alcohol (n=18), or opioid (n=29) dependence, and 14 non-drug-dependent community volunteers. The 86 subjects completed a visual continuous performance test formed by a series of 150 presentations of individual consonant letters. They were asked to press a key whenever a letter was presented twice in succession.

RESULTS

Analyses of P300 ERPs obtained on target trials revealed a similar amplitude decrement in all the patient groups. Further analyses of P300 activity in the 3 drug-dependent patient groups revealed a negative correlation between P300 amplitude and the number of DSM-IIIR childhood conduct disorder criterion behaviors as well as a positive correlation between P300 amplitude and the duration of drug abstinence.

CONCLUSIONS

P300 amplitude in drug-dependent patients is influenced by a complex interaction between CNS pathology that predates, and probably promotes, the onset of drug dependence and CNS pathology that resolves during the process of recovery from drug dependence.

[The p300 cognitive event-related potential. I. Theoretical and psychobiologic perspectives]

The P300 is a positive wave which arises when an attended stimulus is detected. Its parameters depend on a number of variables, in particular the subject's mental state, the task that has to be accomplished, the significance of the stimulus, and the degree of attention. It can be recorded with accuracy, and the different stages of information processing can therefore be analyzed. The P300 wave shows the modifications in neuronal activity which take place during the cognitive process: P300 latency provides an indirect indication of the duration of the processes involved in stimulus discrimination while its amplitude, which is influenced by a number of variables, provides an index of the intensity of the energetic activation or arousal involved. The P300 wave consists of several components which reflect distinct information-processing events (P3a, P3b, P3e, P-SR, P-CR). According to the theoretical models, it is hypothesized that P300 could either represent the adaptation of the working memory to further environmental input ('context updating'), or indicate a closing process ('context closure') in information processing. As regards the physiological aspect of P300 and its association with cortical networks, various studies have suggested that several cortical generators of P300 may co-exist: the medial temporal lobe, the temporo-parietal junction, and the medial and lateral frontal lobe. Psychopharmacological studies have shown that different neurotransmitter systems are involved in the generation and modulation of P300, namely the cholinergic, noradrenergic, dopaminergic, serotoninergic and gabaergic systems. It appears that the noradrenergic agonists increase the amplitude of P300, dopaminergic agonists may have a biphasic effect (increase/reduction), while cholinergic antagonists and gabaergic agonists reduce P300 amplitude and prolong its latency.

Single trial variability within the P300 (250-500 ms) processing window in adolescents with attention deficit hyperactivity disorder

The traditional averaging process used to derive event related potential components (ERPs) is a soundly based method of determining the underlying ERP. Averaging, however, ignores the variability due to the single-trial ERPs that constitute the traditional average ERP. This variability may reflect complementary functional information to the average measure. Our group applied a simple procedure, the response variance curve (RVC), which measures single-trial ERP variability relative to their average. In this study, the average ERP and RVC measures (generated from the same single-trial task-relevant target ERPs) were assessed in an auditory oddball paradigm, in 17 unmedicated male adolescents with attention deficit hyperactivity disorder (ADHD) and in 17 age- and sex-matched normal controls. P300 amplitude, latency and point of maximum variability of the RVC were measured within the P300 processing window (250-500 ms post-stimulus). There were no significant differences in P300 amplitude or latency between the groups. Unmedicated ADHD patients, however, showed significantly increased single-trial variability within the P300 window compared with controls. This variability was significantly reduced with stimulant medication.

Electrophysiological indices of information processing in methylphenidate responders

Event-related potential (ERP) studies report that the positive deflection following stimulus evaluation at 300 msec (P3) in hyperactive children is augmented by methylphenidate (MP). This study investigates P3 and preceding ERP components using an auditory oddball task in attention-deficit hyperactivity disorder (ADHD). Mismatch negativity, negativity at 100 and 200 msec, and positivity at 200 msec and 300 msec (P3) were obtained from 14 control and hyperkinetic children. ADHD children who responded to MP were tested on two separate days while receiving either MP or placebo. Controls were tested once. No differences were found between groups for ERP components preceding P3. P3 amplitude was significantly larger under MP than under placebo, but did not differ from controls. Under MP, differences in P3 amplitude unexpectedly occurred when no response was required. A P3 amplitude increase under MP and the unexpected P3 suggest that MP affects attention regulation.

Effects of methylphenidate on event-related potentials and performance of attention-deficit hyperactivity disorder children in auditory and visual selective attention tasks

Attention-deficit hyperactivity disorder (ADHD) children participated in a double-blind placebo-controlled study in which the effects of a dosage of 15 mg methylphenidate (MPH) on auditory and visual selective attention tasks was determined by presenting frequent (90%) and infrequent (10%) stimuli in both relevant and irrelevant input channels. The subject's task was to respond to the infrequent tones in the relevant input channel. Processing activity (negativity and positivity) was assessed for both tasks. N1, P2, N2, and P3b peaks were scored in the auditory task and N1, P1, N2, P2, P3(1), and P3b peaks were scored in the visual task. Effects of MPH were more prevalent in the visual than in the auditory condition. In the visual condition MPH enhanced the percentage of hits, caused higher central, parietal, and occipital P3b amplitudes to attended stimuli (both standards and deviants), and also enhanced the frontal processing negativity (PN). In the auditory task MPH did not influence performance, but it enhanced the frontal PN as well as the parietal and occipital P3b amplitudes to all stimulus types. In ADHD children, MPH ameliorates some, but not all, deficits and also improves processing where no differences with normal children are present.

Methylphenidate slows reactions of children with attention deficit disorder during and after an error

A Sternberg memory search task was administered under placebo and methylphenidate to 42 children with cross-situational attention deficit disorder (ADD), 31 children with cross-situational ADD plus oppositional features, and 25 patients with marginal ADD. Overall, stimulant medication enhanced accuracy and speed. In addition, patients reacted faster on correct responses not preceded by an error than on errors (especially false alarms) or on correct responses following an error. The slowness during error reactions may reflect decreased confidence or confusion during stimulus classification. This uncertainty may also lead subjects to respond with greater caution, hence more slowly, on correct responses following errors. Notably, methylphenidate increased the slowing of reactions on error trials as well as on correct reactions following an error. Stimulant medication may augment subjects' persistence when they are uncertain or confused, thereby heightening caution and promoting accuracy on succeeding trials. Consistent with previous reports of the generality of enhancement of performance by stimulant medication, the impact of methylphenidate was comparable for the three subtypes of ADD studied.

Auditory event-related potentials (ERPs) and mismatch negativity (MMN) in healthy children and those with attention-deficit or tourette/tic symptoms

The study compares 5 auditory event-related potential (ERP) components (P1 to P3) after 3 tones differing in pitch and rarity, and contrasts the mismatch negativity (MMN) between them in 12 children with attention-deficit hyperactivity disorder (ADHD; mean 10.2 years of age), 12 healthy controls pairwise matched for age (controls), and 10 with Chronic Tic or Tourette Syndrome (TS). Topographic recordings were derived from 19 scalp electrodes. Four major effects are reported. (a) Shorter latencies in ADHD patients were evident as early as 100 ms. (b) Both ADHD and TS groups showed very large P2 components where the maxima were shifted anteriorly. The differences in the later potentials were of a topographical nature. (c) Frontal MMN was non-significantly larger in the ADHD group but normalized data showed a left rather than a right frontal bias as in control subjects. Maxima for TS were usually posterior. (d) ADHD patients did not show the usual right-biased P3 asymmetry nor the frontal versus parietal P3 latency difference. From these results it is suggested that ADHD patients process perceptual information faster from an early stage (N1). Further, along with the TS group, ADHD patients showed an unusually marked inhibitory phase in processing (P2), interpreted as a reduction of the normal controls on further processing. Later indices of stimulus processing (N2-P3) showed a frontal impairment in TS and a right hemisphere impairment in ADHD patients. These are interpreted in terms of the difficulties in sustaining attention experienced by both ADHD and TS patients.

Spatial orienting and focused attention in attention deficit hyperactivity disorder

Seventeen children with attention deficit disorder (ADHD) and 10 normal controls performed two tasks while event-related potentials were recorded. ADHD subjects took part in two more sessions under methylphenidate (MP) or placebo. In the spatial orienting task, invalidly cued targets elicited a longer reaction time (RT) and a P3 that was longer in latency and greater in amplitude than did validly cued targets. Performance was similar for both groups, but the early portion of P3 (300-400 ms) was lower in amplitude for invalidly cued targets in ADHD subjects. MP increased accuracy without affecting RT and shortened P3 peak latency and increased the amplitude of its early portion. In the focused attention task, accuracy was greater for controls and MP, but there were no RT differences. Attended stimuli elicited greater amplitude P1, N1, and P3 than did nonattended stimuli, but these measures were unaffected by diagnosis or medication.

Nimodipine improves information processing in substance abusers

We examined whether nimodipine can improve information processing in healthy drug abusers using cognitive event-related potential (ERP) methodology. Placebo and 30- and 60-mg doses of nimodipine were administered on separate days in a random double-blind design to twelve male subjects, who used cocaine and/or opiates as well as alcohol and marijuana. The subjects performed the auditory rare event monitoring (AREM) task and the paired letter version of the visual continuous performance task (CPT) before oral drug administration as well as one and two hours after drug ingestion. The EEG was recorded from 7 scalp locations. The P3 component of the ERPs to the target stimulus was reduced with repeated testing on the placebo day. The 30-mg dose of nimodipine blocked the decrease in P3, which reflects stimulus evaluation in both tasks. Chronic administration of nimodipine may alleviate the cognitive deficits observed in substance abusers during abstinence and prevent treatment relapse.

[Cognitive evoked potentials in children: normal and abnormal development]

The first part of this review on event-related potentials (ERPs) in children summarizes the role of ERPs in the study of normal cognitive development. The ERPs vary both as a function of the age of the child and also as a function of the cognitive processes that are required by the tasks. Topographical studies allow one to identify cortical regions involved in specific cognitive processes, and monitor their age-related changes. The second part of this paper reviews two examples of abnormal cognitive development (attention deficit hyperactivity disorder and childhood autism) where the ERPs allow a better understanding of the dysfunction underlying the observed cognitive disorders.

The use of methylphenidate for cognitive decline associated with HIV disease

OBJECTIVE

Complaints of cognitive changes are often expressed by patients at all stages of HIV infection. Such changes include decreased memory and attention span, diminished concentration, apathy, and "slowing." Methylphenidate (MPD) has been used in several clinical studies in men with late-stage HIV disease in an attempt to ameliorate these difficulties. The objectives of this review article are to review salient psychopharmacological characteristics of MPD and to describe the research and clinical literature supporting the use of MPD in patients at all stages of HIV infection.

METHODS

Seven studies, case reports, or abstracts from International Conferences on AIDS were available in the English literature through August, 1993, directly addressing the use of MPD in patients with HIV disease. Twenty-nine papers were reviewed for pharmacokinetic data, eighteen for safety and side effects issues, and seventeen for relevant contributions from the neuropsychological testing literature.

RESULTS

Studies in clinical settings have used doses ranges from 10-90 mg. per day in two or three divided doses with reportedly good results in improving both affective and cognitive symptoms associated with HIV disease. Side effects have been relatively mild and patient satisfaction with treatment has been high. However, no studies have been conducted in early stage HIV disease, where a significant minority of patients have similar complaints in the absence of clinically apparent immunosuppression. Likewise, placebo-controlled, dose-finding studies in AIDS patients are entirely lacking, and no studies in women with HIV disease and cognitive changes have been published.

CONCLUSIONS

In spite of these important research short-comings, clinical experience with MPD treatment of cognitive changes in men with HIV/AIDS is consistent with the notion that this medication holds significant promise to improve the quality of life for persons living with HIV/AIDS. Controlled studies to test this hypothesis are warranted.

Event-related potentials to an "oddball" auditory paradigm in children with learning disabilities with or without attention deficit hyperactivity disorder

Event Related Potentials (ERP) were recorded during a two-tone discrimination task in 18 children with Learning Disabilities (LD) and 36 children with Learning Disabilities and Attention Deficit Hyperactivity Disorder (LD-ADHD). Twenty-seven normal children served as a control group. P3 wave amplitude was significantly smaller in the LD and LD-ADHD groups compared with normal children. There was no difference between the LD and LD-ADHD groups. It is suggested that the smaller P3 amplitude in children with LD-ADHD syndromes reflects cognitive and processing difficulties, which frequently coexist with ADHD in these children and is not specifically related to an attention deficit.

Methylphenidate influences on both early and late ERP waves of ADHD children in a continuous performance test

Although it has frequently been reported that hyperactive children have abnormally small P3 amplitudes of the event-related potential (ERP), which are normalized by the stimulant drug methylphenidate (MPH), the literature is inconsistent concerning earlier ERP waves. The aim of the present study was to investigate whether the normalizing effect of a 10-mg dose of MPH was also apparent on earlier waves, such as the N1, the P2, and the N2, besides the P3. Twelve attention deficit with hyperactivity disorder (ADHD) children performed a Continuous Performance Test involving a button-press response to the letter X (CPT-X) under the influence of MPH in a double-blind placebo controlled acute dosage design. ERPs were recorded at Oz, Pz, Cz, and Fz. The expected increase of the parietal P3, both to targets and nontargets, was apparent, as well as a significant increase in percentage of hits. There also was a significant increase of an earlier, negative going, wave, the N2, with a frontal maximum, under the influence of MPH. This wave was probably a manifestation of an increase in processing negativity for target stimuli only, after the intake of the stimulant drug. No effect of MPH was found on the N1 or the P2.

Changes in event-related potentials with stimulant medication in children with attention deficit hyperactivity disorder

Thirty-two children with attention deficit hyperactivity disorder (ADHD) undergoing a 4 week double-blind medication assessment (methylphenidate) and 32 normal controls were studied using event-related potentials (ERPs). The ERPs were recorded from 13 active electrodes during a visual feature detection task. Significant age effects were found in N2, P3a and P3b latencies, that did not interact with group. The P3a and P3b latencies were significantly longer in the ADHD children on baseline testing; there were no latency differences between the groups of children when the normal controls were compared with the ADHD children on their optimal drug dosage (as determined by extensive behavioural and cognitive assessments). There were no significant distributional effects either between groups, or with the ADHD children as a function of medication; there were also no significant differences in reaction time measures. Thus, only the ERPs reflected slowed processing in the ADHD children that normalized on appropriate medication.

Effects of sustained-release and standard preparations of methylphenidate on attention deficit disorder

Nineteen children with attention deficit disorder (ADD) participated in a double-blind trial consisting of four 2-week phases: sustained-release methylphenidate (MPH); standard MPH; a combination of standard and sustained-release MPH; and placebo. Pharmacological treatments were evaluated by means of parent and teacher ratings and open-ended comments, examiner ratings, and patients' performance and event-related potentials during Continuous Performance and Paired-Associate Learning Tests. Results revealed that the MPH conditions were superior to placebo and comparable to one another. Within the limited time frame of the research, the findings suggest comparable effectiveness for sustained-release and standard preparations of MPH.

Normal variation of P300 in children: age, memory span, and head size

The P300 (P3) event-related brain potential was elicited in a group of 50 children and young adults (4-20 years). A simple auditory task was employed in which subjects indicated with a finger movement when a randomly occurring target tone (high pitch) was presented in a series of standard (low pitch) tones. The probability of the target tone was varied across conditions at 10%, 30%, or 50% to assess possible developmental changes in P300 amplitude. Memory capacity was assessed with forward and reverse digit spans. Circumference of the head also was measured. P300 latency decreased with age, and P300 amplitude tended to become larger with age. Polynomial regression analyses revealed significant quadratic trends in these relationships, with changes leveling off for older subjects. Digit span and head circumference also were related curvilinearly to P300 values. Multiple regression analysis indicated that changes in age and memory span both predicted significant changes in P300 latency and amplitude. Target stimulus probability generally affected all subjects in a similar fashion, although the strength of the correlational relationships tended to decline with increases in probability. Developmental changes for the N1, P2, and N2 components from the standard stimuli also were obtained. The results are discussed in terms of previous P3 findings for children and their implications for future studies.

Effects of methylphenidate on processing negativities in patients with attention-deficit hyperactivity disorder

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.