Topographic study of auditory event-related potentials in normal boys and boys with attention deficit disorder with hyperactivity

Inter-subject gamma oscillation synchronization as a biomarker of abnormal processing of social interaction in ADHD

Children with attention-deficit hyperactivity disorder (ADHD) have difficulties in social interactions. Studying brain activity during social interactions is difficult with conventional artificial stimuli. This pioneering study examined the neural correlates of social perception in children with ADHD and matched controls using naturalistic stimuli. We presented 20 children with ADHD and 20 age-and-sex-matched controls with tailored movies featuring high- or low-level social interactions while recording electroencephalographic signals. Both groups exhibited synchronized gamma-band oscillations, but controls demonstrated greater inter-subject correlations. Additionally, the difference in inter-subject correlations between high- and low-interaction movies was significantly larger in controls compared to ADHD patients. Between 55 and 75 Hz comparing viewing high interaction movies with low interaction moves, controls had a significantly larger weighting in the right parietal lobe, while ADHD patients had a significantly smaller weighting in the left occipital lobe. These findings reveal distinct spatiotemporal neural signatures in social interaction processing among children with ADHD and controls using naturalistic stimuli. These neural markers offer potential for group differentiation and assessing intervention efficacy, advancing our understanding ADHD-related social interaction mechanisms.

Seeing is believing: Larger Colavita effect in school-aged children with attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder that leads to visually relevant compensatory activities and cognitive strategies in children. Previous studies have identified difficulties with audiovisual integration in children with ADHD, but the characteristics of the visual dominance effect when processing multisensory stimuli are not clear in children with ADHD. The current study used the Colavita paradigm to explore the visual dominance effect in school-aged children with ADHD. The results found that, compared with typically developing children, children with ADHD had a higher proportion of "visual-auditory" trials and a lower proportion of "simultaneous" trials. The study also found that the proportion of visual-auditory trials in children with ADHD decreased as their Swanson, Nolan, and Pelham-IV rating scale (SNAP-IV) inattention scores increased. The results showed that school-aged children with ADHD had a larger Colavita effect, which decreased with the severity of inattentive symptoms. This may be due to an overreliance on visual information and an abnormal integration time window. The connection between multisensory cognitive processing performance and clinical symptoms found in the current study provides empirical and theoretical support for the knowledge base of multisensory and cognitive abilities in disorders.

Sound localization and auditory selective attention in school-aged children with ADHD

This study aimed to identify the neurophysiologic bases of auditory attention deficits in children with attention-deficit/hyperactivity disorder (ADHD), focusing on the electroencephalography component of auditory spatial selective attention [the N2 anterior contralateral component (N2ac)]. EEG data were collected from 7- to 11-year-old children with ADHD (n = 54) and age-, sex-, and IQ-matched typically developing (TD) children (n = 61), while they performed an auditory spatial selective task. For behavior, the children with ADHD showed a shorter reaction time (RT) but a higher RT coefficient of variability (RT_CV) than TD children. For ERPs, the TD group showed a significant "adult-like" N2ac component; however, the N2ac component was absent in children with ADHD. More importantly, the smaller N2ac component could predict longer RT in both groups, as well as higher severity of inattentive symptoms in children with ADHD. Our results indicated that 7- to 11-year-old TD children have developed an "adult-like" ability to balance auditory target selection and distractor suppression; the absence of N2ac in children with ADHD provided novel evidence supporting their dysfunctional auditory spatial selective attention.

Effects of Integrated Brain, Body, and Social (IBBS) intervention on ERP measures of attentional control in children with ADHD

A primary goal of this study was to examine the impact of an Integrated Brain, Body, and Social (IBBS) intervention (multi-faceted treatment consisting of computerized cognitive training, physical exercise, and behavior management) on ERPs of attentional control (P3 & N2) in children with ADHD. The secondary goal was to test the differences between children with and without ADHD on ERP and Go/No-Go behavioral measures. A total of twenty-nine participants (M age = 7.14 years; 52% male; 41.4% white) recruited from the IBBS efficacy study comparing IBBS to Treatment-As-Usual (TAU) completed a Go/No-Go task before and after treatment as brain activity was recorded using EEG. Thirty-four matched healthy controls (HC) completed the same EEG procedures at a single time point. Following treatment, the Go P3 latency was significantly earlier for the IBBS group relative to the TAU group. No treatment effects were found on any behavioral measures. Prior to treatment, there was a significant difference between the ADHD group and HC group for the N2 difference wave. Children with ADHD also showed slower reaction times on behavioral measures. Although this pilot study did not reveal robust treatment effects, it suggests that IBBS may prevent the worsening of attentional systems in the brain and larger studies are needed for replication purposes.

[Differential effects of attention deficit/hyperactivity disorder subtypes in event-related potentials]

BACKGROUND

To better understand the neurophysiological substrates in attention deficit/hyperactivity disorder (ADHD), a study was performed on of event-related potentials (ERPs) in Colombian patients with inattentive and combined ADHD.

METHODS

A case-control, cross-sectional study was designed. The sample was composed of 180 subjects between 5 and 15 years of age (mean, 9.25±2.6), from local schools in Manizales. The sample was divided equally in ADHD or control groups and the subjects were paired by age and gender. The diagnosis was made using the DSM-IV-TR criteria, the Conners and WISC-III test, a psychiatric interview (MINIKID), and a medical evaluation. ERPs were recorded in a visual and auditory passive oddball paradigm. Latency and amplitude of N100, N200 and P300 components for common and rare stimuli were used for statistical comparisons.

RESULTS

ADHD subjects show differences in the N200 amplitude and P300 latency in the auditory task. The N200 amplitude was reduced in response to visual stimuli. ADHD subjects with combined symptoms show a delayed P300 in response to auditory stimuli, whereas inattentive subjects exhibited differences in the amplitude of N100 and N200. Combined ADHD patients showed longer N100 latency and smaller N200-P300 amplitude compared to inattentive ADHD subjects.

CONCLUSIONS

The results show differences in the event-related potentials between combined and inattentive ADHD subjects.

Behavioral and neurophysiological study of attentional and inhibitory processes in ADHD-combined and control children

This study compares behavioral and electrophysiological (P300) responses recorded in a cued continuous performance task (CPT-AX) performed by children with attention deficit hyperactivity disorder-combined subtype (ADHD-com) and age-matched healthy controls. P300 cognitive-evoked potentials and behavioral data were recorded in eight children with ADHD (without comorbidity) and nine control children aged 8-12 years while performing a CPT-AX task. Such task enables to examine several kinds of false alarms and three different kinds of P300 responses: the "Cue P300", the "Go P300" and the "NoGo P300", respectively, associated with preparatory processing/attentional orienting, motor/response execution and motor/response inhibition. Whereas hit rates were about 95% in each group, ADHD children made significantly more false alarm responses (inattention- and inhibition-related) than control children. ADHD children had a marginally smaller Cue P300 than the control children. Behavioral and electrophysiological findings both highlighted inhibition and attention deficits in ADHD-com children in the CPT-AX task. A rarely studied kind of false alarm, the "Other" FA, seems to be a sensitive FA to take into account, even if its interpretation remains unclear.

Maturation of auditory event-related potentials across adolescence

Adolescence is a time of great change in the brain in terms of structure and function. It is possible to track the development of neural function across adolescence using auditory event-related potentials (ERPs). We measured passive auditory ERPs to pure tones and consonant-vowel (CV) syllables in 90 children and adolescents aged 10-18 years, as well as 10 adults. With one exception, the pattern of results were the same for tones and speech: Across adolescence, the P1 ERP peak decreased in size and latency, the N1 increased in size and decreased in latency, the P2 remained constant in size, and the N2 decreased in size but remained stable across adolescence. The exception was P2 latency, which increased for speech but remained stable for tones. Interesting step-like changes were observed for N1 latency for both tones and speech stimuli in 15- to 16-year-olds. These may stem from rapid hormonal changes that affect neurotransmitter activity of the ERP-generating neurons.

The mismatch negativity (MMN)--a unique window to disturbed central auditory processing in ageing and different clinical conditions

In this article, we review clinical research using the mismatch negativity (MMN), a change-detection response of the brain elicited even in the absence of attention or behavioural task. In these studies, the MMN was usually elicited by employing occasional frequency, duration or speech-sound changes in repetitive background stimulation while the patient was reading or watching videos. It was found that in a large number of different neuropsychiatric, neurological and neurodevelopmental disorders, as well as in normal ageing, the MMN amplitude was attenuated and peak latency prolonged. Besides indexing decreased discrimination accuracy, these effects may also reflect, depending on the specific stimulus paradigm used, decreased sensory-memory duration, abnormal perception or attention control or, most importantly, cognitive decline. In fact, MMN deficiency appears to index cognitive decline irrespective of the specific symptomatologies and aetiologies of the different disorders involved.

The effects of childhood disruptive disorder comorbidity on P3 event-related brain potentials in preadolescents with ADHD

The present study examined the degree to which the P300 component of the visual brain event-related potential and associated task performance deficits often observed in children with attention-deficit hyperactivity disorder (ADHD) are attributable to comorbid childhood disruptive disorders using a community sample of 11-year olds from the Minnesota Twin Family Study. Subjects were divided into "ADHD-pure" (ADHD without oppositional defiant disorder, ODD, or conduct disorder, CD), "ADHD-comorbid" (ADHD with ODD or CD), and comparison (no childhood disruptive disorder) groups using DSM-III-R diagnoses. Results showed that ADHD-comorbid but not ADHD-pure subjects displayed significant P3 amplitude reduction and poorer task performance compared to controls. No group effects for P3 latency or reaction time were seen. Although ADHD-comorbid children had marginally more ADHD symptoms compared to ADHD-pure children, this did not account for their reduced P3, suggesting that the observed neurobehavioral deficits reflected the effects of co-occurring childhood disruptive disorders.

Enhanced gamma-band activity in ADHD patients lacks correlation with memory performance found in healthy children

Previous electrophysiological as well as imaging research has contributed to the understanding of impairments in attention, executive functions, and memory in patients with attention-deficit/hyperactivity disorder (ADHD). However, there is a lack of studies investigating ADHD related differences in the gamma range of human electroencephalogram (EEG), although gamma activity is strongly associated with cognitive processes impaired in ADHD patients and is also modulated by dopamine polymorphisms linked with ADHD. To close this gap, the present study compared gamma activity in ADHD children with that of healthy controls and correlated it with memory performance. EEG was recorded from 13 ADHD patients as well as 13 healthy control subjects during the encoding phase of a visual memory paradigm. In a subsequent recognition test, participants had to judge pictures as being old or new. Analysis of evoked gamma-band responses (GBRs) during stimulus encoding revealed a strong task-related enhancement for ADHD patients in parieto-occipital areas. Interestingly, this augmentation was not associated with recognition performance, whereas healthy subjects exhibited a strong positive correlation between evoked gamma activity during stimulus encoding and subsequent recognition performance. We interpret this finding as evidence of enhanced excitation levels and unspecific activation of processing resources in ADHD patients. Furthermore, enhanced GBRs in ADHD could also indicate a decrease of neuronal signal-to-noise ratio, partially caused by the genetic variations within the dopaminergic pathway of ADHD patients. The involved genetic polymorphisms have been shown to modulate evoked GBRs, which therefore could be a possible marker of impaired neurotransmission in ADHD.

Auditory Evoked Potentials in the Detection of Interaural Intensity Differences in Children and Adults

OBJECTIVE

The goal of the current study was to identify neurophysiological indices of binaural processing in children with no history of hearing loss or listening problems. The results will guide our efforts to diagnose children for whom impaired binaural processing may contribute to difficulty understanding speech in adverse listening environments. Our main aim was to document the cortical auditory evoked potentials (AEPs) in response to interaural intensity differences (IIDs) in children. It is well known, however, that the morphology of AEPs is substantially different in children and adults. Comparison of AEPs in response to IIDs between children and adults allowed us to evaluate age-related differences in the AEP waveform of binaural processing.

DESIGN

Nine children (ages 7 yr 0 mo to 9 yr 4 mo) and 11 adults (23 to 34 yr) with normal hearing and no known or suspected neurological or academic problems listened to click stimuli under earphones. Click trains consisted of broadband noise of 1-msec duration with a click rate of 100 Hz. In the experimental condition (IID-present) 50-msec intervals containing an interaural intensity difference of 20 dB were introduced periodically in the continuous stream of otherwise diotic click trains. The diotic trains alternated in intensity between 50 and 70 dB peSPL. In the baseline condition (IID-absent), the same continuous diotic click stream utilized in the IID-present condition was presented with no IID. Finally, for comparison with existing literature on AEPs in children and adults, we presented monaural click trains of 50-msec duration, like those used in the IID stimulus (but with no continuous stream) to the left ear at 70 dB peSPL, with an interstimulus interval of 750 msec. Stimuli were presented in separate blocks for each stimulus type and AEPs were recorded in a passive listening condition.

RESULTS

A prominent AEP activation was present in both age groups for the IID-present condition; the IID-absent condition did not evoke substantial AEPs. Adult waveform characteristics of the AEPs to monaural clicks and IID-present around 100 and 200 msec were comparable to previous reports. The children demonstrated the expected AEP activation patterns in response to monaural clicks (i.e., positivity around 100 msec, followed by prominent negativity around 250 msec); however their AEP waveforms to IIDs were mainly comprised of a prolonged positivity around 200 to 250 msec after stimulus onset. A two-step temporal-spatial Principal Component Analysis (PCA) was used to evaluate the temporal (time) and spatial (electrode location) composition of the AEP waveforms in children and adults in response to IID-present and IID-absent conditions. Separate repeated-measures ANOVAs with factor scores as the dependent variable were conducted for each temporal factor (TF) representing the waveform deflections around 100, 200 and 250 msec (i.e., TF110, TF200, and TF255) at the frontocentral spatial factor (SF1). Significantly greater negative activation was observed in adults than in children in response to IID-present for TF110. The IID-present condition evoked a significantly greater waveform inflection for TF200 in both age groups than IID-absent. A positive going activation for TF255 was observed in the IID-present condition in children but not in adults.

CONCLUSIONS

This study compared obligatory AEPs in response to binaural processing of IIDs in children and adults with normal hearing. The morphology of the AEP waveform in children was different for monaural clicks and IID-present stimuli. The difference between AEPs for monaural clicks and IID-present did not occur in adults. It is likely that polarity reversal of the AEPs in response to the IID accounts for the observed AEP morphology in children.

Maturation of the cortical auditory evoked potential in infants and young children

The aim of this study was to evaluate the maturation of the cortical auditory evoked potential (CAEP) in humans. The participants in this experiment were 10 newborns (<7 days), 19 toddlers (13-41 months), 20 children (4-6 years) and 9 adults (18-45 years). CAEPs were obtained in response to low (400 Hz) and high (3000 Hz) tones and to the word token /baed/, all presented at 60 dB HL, at a rate of 0.22 Hz. Latency and amplitude measures were made for CAEP components P1, N1, P2 and N2 as a function of participant age, stimulus type and electrode montage. CAEP component latencies were relatively stable from birth to 6 years, but adults demonstrated significantly shorter latencies compared to infants and children. Components P1 and N2 decreased in amplitude, while components N1 and P2 increased in amplitude from birth to adulthood. Words evoked significantly larger CAEPs in newborns compared to responses evoked by tones, but in other age groups the effects of stimulus type on component amplitudes and latencies were less consistent. There was evidence of immature tonotopic organisation of the generators of N1 when responses from infants and young children were compared to those of adults. The scalp distribution of components N1 and P2 was clearly different in newborns and toddlers compared to children and adults. In the younger groups, both N1 and P2 were uniformly distributed across the scalp but in children and adults these components showed more focal distributions, with evidence of response laterality increasing with maturity. The results of the present study describe, for the first time, CAEPs recorded from multiple scalp electrodes, for tones and speech stimuli, in infants and children from birth to 6 years of age. Frequency-related differences in component amplitude were apparent at all ages reflecting development of tonotopic organisation of the CAEP neural generators.

Maturation of CAEP in infants and children: A review

This paper reviews our current understanding of the development of the obligatory cortical auditory evoked potential (CAEP) components P1, N1, P2, and N2. Firstly, the adult CAEP is briefly reviewed with respect to its morphology, neural generators and stimulus-dependence. Secondly, age-related changes occurring from the newborn period through childhood and adolescence are reviewed. The focus is on the maturation of CAEP morphology, changes in the scalp topography of the various components, changes in their amplitude and latency and in their stimulus-dependence. This review identifies periods of development in which we have only limited understanding of cortical auditory processing, as revealed by evoked potentials.

Impulsivity affects mismatch negativity (MMN) measures of preattentive auditory processing

The current study addresses the relation between impulsive personality and mismatch negativity (MMN) as measure of auditory processing. In a sample of 33 normals, MMN was measured and related to self-reported measures of impulsive behavior. Participants were tested using a passive auditory oddball paradigm while EEG recordings were obtained. It was found that the negative MMN amplitude at the left lateral cluster was negatively correlated with self-reported impulsivity, with high impulsive individuals showing larger MMN amplitudes than low impulsive individuals. This indicates that impulsivity is related to preattentive auditory processing, a process that is not dependent on response execution. In addition to the well-known involvement of top-down control in impulsivity, these findings implicate that the cognitive bottom-up processing of incoming stimuli is associated with individual differences in impulsivity. Since the source of the MMN is thought to be located in the auditory cortex, this suggests involvement of "lower order" temporal lobe processes in impulsive behaviors.

The impact of reward, punishment, and frustration on attention in pediatric bipolar disorder

BACKGROUND

Theories in affective neuroscience suggest that mood disorders involve perturbations in attention-emotion interactions. We tested the hypothesis that frustration adversely impacts attention and behavior in children with bipolar disorder (BPD).

METHODS

Thirty-five children with BPD and 26 normal control subjects completed: 1) a Posner attention task with feedback but no contingencies; 2) an affective Posner with contingencies; and 3) an affective Posner that used rigged feedback to induce frustration. Reaction time (RT) and event-related potential (ERP) data were collected.

RESULTS

At baseline (task 1), there were no between-group differences in behavior or ERPs. Children with BPD exhibited reduced parietal P3 amplitude on task 3 only. On trials occurring after negative feedback, control subjects showed decreased RT when contingencies were introduced (task 2), whereas BPD subjects did not.

CONCLUSIONS

The introduction of contingencies was associated with impaired performance of children with BPD, suggesting deficits in their ability to adapt to changing contingencies. In addition, frustration was associated with disrupted attention allocation in children with BPD. We hypothesize that children with BPD inappropriately deployed attention to their internal frustration rather than to the task, causing impaired performance.

Attention deficit and impulsivity: Selecting, shifting, and stopping

The present selective review addresses attention, inhibition, and their underlying brain mechanisms, especially in relation to attention deficit/hyperactivity disorders (AD/HD), and the effects of methylphenidate. In particular, event-related potential (ERP) studies suggest a deficit in the early-filtering aspect of selective attention in children with AD/HD. Results from stop tasks are consistent with impairments in stopping performance in AD/HD, but in children (as opposed to adults) these effects cannot be easily dissociated from more general impairments in attention to the task, and therefore an interpretation in terms of inhibitory control is not straightforward. On the other hand, the beneficial effects of methylphenidate are more specific to stopping, and there are no clearcut effects of methylphenidate on measures of selective attention. Even when group differences pertain specifically to stopping performance (as with adults with AD/HD), ERP evidence suggests at least a partial contribution of differences in switching attention to the stop signal, as revealed in measures of sensory cortex activation. ERP evidence from cued go/nogo tasks underlines the importance of taking into account the contribution of higher order control processes involved in anticipation of and preparation for task stimuli. It suggests that in certain conditions, expectancy, rather than response bias, contributes to increased behavioral response tendencies, and that a presumed index of response inhibition, the nogo N2, may rather reflect conflict monitoring. In sum, direct reflections of brain activity suggest that mechanisms of expectation and attention, rather than of response bias or inhibitory control, govern behavioral manifestations of impulsivity.

An event-related potential study of selective auditory attention in children and adults

In a dichotic listening paradigm, event-related potentials (ERPs) were recorded to linguistic and nonlinguistic probe stimuli embedded in 2 different narrative contexts as they were either attended or unattended. In adults, the typical N1 attention effect was observed for both types of probes: Probes superimposed on the attended narrative elicited an enhanced negativity compared to the same probes when unattended. Overall, this sustained attention effect was greater over medial and left lateral sites, but was more posteriorly distributed and of longer duration for linguistic as compared to nonlinguistic probes. In contrast, in 6- to 8-year-old children the ERPs were morphologically dissimilar to those elicited in adults and children displayed a greater positivity to both types of probe stimuli when embedded in the attended as compared to the unattended narrative. Although both adults and children showed attention effects beginning at about 100 msec, only adults displayed left-lateralized attention effects and a distinct, posterior distribution for linguistic probes. These results suggest that the attentional networks indexed by this task continue to develop beyond the age of 8 years.

Effects of methylphenidate on quantitative EEG of boys with attention-deficit hyperactivity disorder in continuous performance test

The purpose of this study was to investigate the effects of methylphenidate, a psychostimulant, on quantitative electroencephalography (QEEG) during the continuous performance test (CPT) in boys with attention-deficit hyperactivity disorder (ADHD). The QEEG was obtained from 20 boys with ADHD. The amplitudes of 4 bands (alpha, beta, delta, and theta) in the QEEG, as well as the theta /beta ratio, before and after the administration of methylphenidate were compared during both the resting and CPT states. Methylphenidate induced a significant increase of alpha activities in both the right and left frontal and occipital areas, an increase of beta activities in almost all areas except for the temporal region, a decrease of theta activities in both the occipital and right temporo-parietal areas, a mild decrease of delta activities in the occipito-parietal areas, and an increase of the theta/beta ratio in the right frontal and parieto-occipital, and left temporal areas during the CPT state. No significant QEEG changes were induced by the administration of methylphenidate in the resting state. These data suggest that methylphenidate has greater electrophysiological influences on the cerebral topographical activities during the performance of attentional tasks, as compared to the resting state, in boys with ADHD.

Dipole source localization of event-related brain activity indicative of an early visual selective attention deficit in ADHD children

OBJECTIVE

This study was aimed at investigating whether attention-deficit hyperactivity disorder (ADHD) children suffer from specific early selective attention deficits in the visual modality with the aid of event-related brain potentials (ERPs). Furthermore, brain source localization was applied to identify brain areas underlying possible deficits in selective visual processing in ADHD children.

METHODS

A two-channel visual color selection task was administered to 18 ADHD and 18 control subjects in the age range of 7-13 years and ERP activity was derived from 30 electrodes.

RESULTS

ADHD children exhibited lower perceptual sensitivity scores resulting in poorer target selection. The ERP data suggested an early selective-attention deficit as manifested in smaller frontal positive activity (frontal selection positivity; FSP) in ADHD children around 200 ms whereas later occipital and fronto-central negative activity (OSN and N2b; 200-400 ms latency) appeared to be unaffected. Source localization explained the FSP by posterior-medial equivalent dipoles in control subjects, which may reflect the contribution of numerous surrounding areas.

CONCLUSIONS

ADHD children have problems with selective visual processing that might be caused by a specific early filtering deficit (absent FSP) occurring around 200 ms. The neural sources underlying these problems have to be further identified. Source localization also suggested abnormalities in the 200-400 ms time range, pertaining to the distribution of attention-modulated activity in lateral frontal areas.

Inhibitory processing during the Go/NoGo task: an ERP analysis of children with attention-deficit/hyperactivity disorder

OBJECTIVE

Previous event-related potential (ERP) research on inhibitory functioning in attention-deficit/hyperactivity disorder (AD/HD) has often failed to use tasks which optimally assess inhibition. We report on an improved measure of inhibitory function, involving inhibition of a prepotent response, in children with AD/HD.

METHODS

Twelve males with AD/HD and 12 control males, aged 7-12 years, completed a cued Go/NoGo task where Go stimuli were presented on 70% of trials. ERP and behavioural measures were collected, together with reading, spelling and full-scale IQ scores.

RESULTS

The behavioural performance of children with AD/HD was not significantly different from normal controls, although children with AD/HD made faster responses and more errors. Group differences were apparent in the early processing components (P1, N1, P2) of responses to Warning, Go and NoGo stimuli. For the frontally maximal N2, a NoGo>Go effect was found, consistent with previous work linking this component with inhibitory processing. In control children this effect was particularly strong in the right frontal region, while children with AD/HD showed a much larger NoGo>Go effect, and an earlier N2 peak, than controls, with a focal shift to the left frontal region.

CONCLUSIONS

Compared with normal controls, children with AD/HD demonstrate early stimulus processing atypicalities, suggesting problems with sensory registration and identification of stimuli. Further, N2 results suggest that children with AD/HD must trigger the inhibition process earlier and more strongly than controls to perform at a comparable behavioural level.

SIGNIFICANCE

The results support the theory that behavioural inhibition is deficient in AD/HD, as children with AD/HD show abnormalities in inhibitory ERP components relating to the effort involved in inhibiting a prepotent response.

Aiding diagnosis of attention-deficit/hyperactivity disorder and its subtypes: discriminant function analysis of event-related potential data

BACKGROUND

Robust evidence exists that the brain functioning of children and adolescents with attention-deficit/hyperactivity disorder (AD/HD) differs from that of normal controls. The purpose of this study was to further investigate whether event-related potential (ERP) measures of brain function could be used to reliably classify normal controls versus children and adolescents with two subtypes of AD/HD.

METHODS

Behavioural and topographic ERP data from children aged 8-12 years (n = 75) and adolescents aged 13-18 years (n = 75) were entered into stepwise discriminant function analyses separating controls and subjects with AD/HD, and also subjects with AD/HD-Predominantly Inattentive type (AD/HDin) from those with AD/HD-Combined type (AD/HDcom).

RESULTS

For children aged 8-12 years, controls and children with AD/HD could be separated with an overall classification accuracy of 73.3%, and the AD/HD subtypes were classified with 69.4% overall accuracy. For adolescents aged 13-18 years, 58.7% of the control vs. AD/HD subjects were correctly classified, and 62.7% of subjects in the subtypes. Classification function coefficients for each of these discriminations are presented for the purposes of cross-validation.

CONCLUSIONS

In children aged 8-12 years, analysis of ERP data may aid a clinician in diagnosing AD/HD, although the clinical utility of ERP analysis is reduced for adolescents aged 13-18 years. Suggestions are made to combine ERP measures with other measures of brain function in order to improve classification accuracy, and also to predict drug response in children diagnosed with AD/HD.

Event-related slow-wave activity in two subtypes of attention-deficit/hyperactivity disorder

OBJECTIVE

Previous time-frequency studies have indicated that event-related low-frequency activity has important effects on component topography and developmental effects in auditory event-related potentials (ERPs) of children and adolescents. This study investigated the influence of event-related slow-wave (SW) (0.01-2 Hz) activity in the group differences seen between children with and without attention-deficit/hyperactivity disorder (AD/HD) of different subtypes.

METHODS

Time-frequency analysis techniques were applied to auditory ERP data derived from children with AD/HD predominantly inattentive type (n = 30), AD/HD combined type (n = 30) and age-matched control subjects (n = 30).

RESULTS

Event-related early frontal negative and late posterior positive SW components were reduced in the AD/HD combined type group, but not AD/HD inattentive type group, relative to controls. The RESIDUAL ERPs, which represented event-related 2-12 Hz activity, showed clinical vs. control group differences in components that were similar in both AD/HD subtype groups.

CONCLUSIONS

The time-frequency results showed that event-related SW (0.1-2 Hz) activity contributes importantly to group differences between AD/HD and control children, and the pattern of group differences from controls for each of the AD/HD subtype groups, which are evident in raw ERPs. These results emphasise both the clinical and developmental importance of this form of analysis.

SIGNIFICANCE

This novel approach revealed additional specific information about stimulus processing and regional inhibition/activation in two AD/HD subtypes, relative to control subjects.

A review of electrophysiology in attention-deficit/hyperactivity disorder: II. Event-related potentials

OBJECTIVE

This article reviews the event-related potential (ERP) literature in relation to attention-deficit/hyperactivity disorder (AD/HD).

METHODS

ERP studies exploring various aspects of brain functioning in AD/HD are reviewed, ranging from early preparatory processes to a focus on the auditory and visual attention systems, and the frontal inhibition system. Implications of these data for future research and development in AD/HD are considered.

RESULTS

A complex range of ERP deficits has been associated with the disorder. Differences have been reported in preparatory responses, such as the contingent negative variation. In the auditory modality, AD/HD-related differences are apparent in all components from the auditory brain-stem response to the late slow wave. The most robust of these is the reduced posterior P3 in the auditory oddball task. There are fewer studies of the visual attention system, but similar differences are reported in a range of components. Results suggesting an inhibitory processing deficit have been reported, with recent studies of the frontal inhibitory system indicating problems of inhibitory regulation.

CONCLUSIONS

The research to date has identified a substantial number of ERP correlates of AD/HD. Together with the robust AD/HD differences apparent in the EEG literature, these data offer potential to improve our understanding of the specific brain dysfunction(s) which result in the disorder. Increased focus on the temporal locus of the information processing deficit(s) underlying the observed range of ERP differences is recommended. Further work in this field may benefit from a broader conceptual approach, integrating EEG and ERP measures of brain function.

Topographic distribution and developmental timecourse of auditory event-related potentials in two subtypes of attention-deficit hyperactivity disorder

The effect of age on the topographic distribution of auditory event-related potentials (ERPs) recorded during a two-tone discrimination, or oddball, task was examined in two subtypes of attention deficit/hyperactivity disorder (AD/HD) as defined by the most recent diagnostic manual, DSM-IV. EEG was recorded at 17 sites from AD/HD predominantly inattentive type (n=50) and AD/HD combined type (n=50) subjects aged from 8 to 17 years 11 months. ERP components were quantified at each site. Results revealed topographic differences from controls (n=50) that were common to both subtypes (e.g. target and standard P2 amplitude, and standard P2 latency) or unique to a particular subtype of AD/HD (Inattentive type: target N1, N2, P3b and standard N2 amplitude, target P2 latency; Combined type: target N1, P2, N2 and P3b amplitude, target N2 and standard N1 latency). These group differences showed different age effects. The across-region results revealed differing patterns of abnormal component development for each subtype, indicating a qualitative difference in information processing stage deficits in each of these AD/HD subtypes.

The modulation of late component event related potentials by pre-stimulus EEG theta activity in ADHD

Electroencephalography (EEG) and Event Related Potentials (ERPs) studies in ADHD have generally been studied separately. This study examined these measures simultaneously in 54 adolescent unmedicated ADHD males and age and gender matched normal controls during an auditory oddball paradigm. Compared with controls, ADHD patients showed increased pre-stimulus EEG Theta activity and post-stimulus reduced N200 amplitude, increased P200 amplitude and delayed N200 and P300 latencies evoked to target stimuli. Moreover, Theta activity was negatively correlated with N200 amplitude and positively correlated with P200, N200 and P300 latency in ADHD. There were no correlations in the control group. Pre-stimulus preparatory state increases in Theta activity in ADHD may underlie some of the reported disturbances in information processing reflected in ADHD.

Attention deficit hyperactivity disorder in adults: conceptual and clinical issues

Reports published over the past decade indicate that attention deficit hyperactivity disorder (ADHD) is a cause of significant psychological impairment in adults. The adulthood disorder occurs as a continuation of its childhood counterpart, with the full ADHD syndrome persisting into early adulthood in about a third of those with childhood ADHD. Despite advances in the understanding of the neurobiology of adult ADHD, the diagnosis is made clinically by establishing a retrospective childhood diagnosis, evaluating the current symptom profile and excluding alternative medical or psychiatric causes of symptoms. Adults with ADHD have high rates of comorbid psychiatric disorder and suffer significant relationship dysfunction, work and educational failure. There is emerging evidence for the effectiveness of specific treatments for adult ADHD, including stimulant medications and some antidepressants. Clinicians should be aware of this potentially treatable disorder in young adults presenting with psychological difficulties and a history of childhood ADHD symptoms.

Frontal, temporal and lateralized brain function in children with attention-deficit hyperactivity disorder: a psychophysiological and neuropsychological viewpoint on development

This article considers deficits in the selective aspects of perception underlying symptoms of impaired attention and impulsivity in children with attention-deficit hyperactivity syndrome (ADHD) in terms of frontal and temporal lobe function and cerebral asymmetry. Tomographic studies suggest a disturbed fronto-striatal function, but have neglected limbic contributions under activating conditions and are equivocal on the nature of apparent lateralized differences. Neuropsychological and psychophysiological studies suggest that early and late stages of information processing are affected in both the frontal and temporal lobes and imply impaired intercortical dialog. Given the evidence for a normal specialization in global processing in the right and the processing of details in the left hemisphere, the lateralized impairment may progress from situational ADHD (impaired selective aspects of perception on the right) to pervasive ADHD (additional impairment in decision-making on the left). Accordingly some ADHD children may experience an early negative neurodevelopmental influence that only appears as the brain region matures while others show a delayed development of CNS function.

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.

The efficacy of utilizing the P300 as a measure of auditory deprivation in monaurally aided profoundly hearing-impaired children

Auditory event-related responses have been successfully used to differentiate the effects of auditory deprivation in laboratory animals and could provide an alternative and less subjective method of testing auditory deprivation. The purpose of this study was to investigate the efficacy of using the P300 response to measure auditory deprivation in monaurally aided children with hearing impairment. Seventeen children (8 female, 9 male) aged 9 to 18 years (M = 13.1 years) participated in the study. Ten subjects with bilateral congenital severe to profound sensorineural hearing losses (M = 87 dB) were recruited from a residential school for the deaf. All had worn monaural amplification for at least 8 years. Seven children with normal hearing sensitivity were matched for age effects. A two-tone auditory oddball paradigm was utilized to elicit the P300 responses. Statistical analysis revealed that the P300 amplitude was significantly greater in the aided ear compared to the unaided ear of the hearing-impaired group (p < 0.05). Two unaided ears of this group had no measurable responses. No other significant latency or amplitude differences were found within or between groups. Results of this investigation serve to reconfirm that binaural amplification should routinely be recommended for hearing-impaired children.

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.

Frontocortical activity in children with comorbidity of tic disorder and attention-deficit hyperactivity disorder

Comorbidity of tic disorder (TD) and attention-deficit hyperactivity disorder (ADHD) in children is common but not fully understood. Thus we investigated the effect of TD and ADHD on the amplitude of the postimperative negative variation (PINV) in children with combined tic + hyperactivity symptoms (TD + HA). PINV was chosen as an indicator of frontal lobe functioning that is closely related to self-regulation of behavior. PINVs of four groups of children (healthy controls, pure TD, pure ADHD, and combined TD + HA; total number 43) were elicited in an auditory warned reaction task in three conditions (control = CC, loss-of-control = LoCC, and lack-of-control = LaCC) at midfrontal (Fz) and midcentral (Cz) leads of the scalp. Effects of TD and ADHD were revealed only in the noncontrol conditions, being independent in the LaCC, but interactive in the LoCC. Thus, the additive model of psychopathological classification concerning the comorbidity of TD and ADHD was only partially supported by the observed pattern of psychophysiological results.

Event-related potentials and performance of attention-deficit hyperactivity disorder: children and normal controls in auditory and visual selective attention tasks

Attention-deficit hyperactivity disorder (ADHD) children and normal controls (7-13 yrs old) performed an auditory and visual selective attention task. Subjects were instructed to respond to the infrequent (10%) stimuli in the relevant channel. Processing negativity (PN) and several other ERP peaks were scored at the midline electrodes. In the auditory task, controls had more correct detections (hits), less false alarms, larger P3b amplitudes to nontarget stimuli (but not to hits), a larger central PN and larger early frontal positivity (100-250 ms) to target stimuli than ADHD subjects. In the visual modality, controls had more correct detections, less false alarms, larger P3b amplitudes to nontarget stimuli (but not to hits), and larger frontal P3(1) amplitudes to infrequent than to frequent stimuli. It was hypothesized that in ADHD children in both the auditory and the visual task, there is a deficit in the activation of the P3b process. Incorrect triggering of the P3b process might be caused by disturbances in other aspects of the attention process, preceding the P3b.

Auditory event-related potentials to a two-tone discrimination paradigm in attention deficit hyperactivity disorder

Auditory event-related potentials (ERPs) were recorded from 10 children diagnosed with attention deficit hyperactivity disorder (ADHD) and 10 age-, sex-, and IQ-matched control children. ERPs were recorded from 17 electrodes during an auditory two-tone discrimination ("oddball') paradigm. Subjects were instructed to press a hand-held response button to infrequently presented target tones. ERP components elicited to target and non-target stimuli were analyzed for between-group differences. Results indicated that for the children with ADHD relative to control children, an N2 component to non-target stimuli was larger in the posterior region and smaller in the frontal region. The P3b component to target stimuli was smaller in the posterior region and larger in the frontal region for the ADHD group compared with the control group. The between-group differences in P3b scalp distribution are indicative of a between-group difference in the neural generators of P3b. It is proposed that the ADHD group, relative to controls, utilizes an additional cognitive process when processing task-relevant stimuli. This process is more frontally distributed and may reflect an attentional compensation mechanism in the ADHD group.

Topographical analyses of attention disorders of childhood

Cognitive ERPs and EEG spectral differences were compared in three groups of children: nonreferred controls, those with a dominant hyperactivity/impulsivity factor (ADHD-Im), and those with a dominant inattentive factor (ADHD-Ia). The results from the ERP analyses indicated that the P250, P350, and P500 components differed between the groups. The most marked differences were seen with respect to the amplitude of the P500 components. In addition, the topographic foci of the P500 components for the CON and ADHD-Im groups were symmetrical, but the ADHD-Ia group featured P250 and P350 components that were biased away from the right hemisphere. Nevertheless, the P500 was found to be an effective discriminator between the groups. The combined spectral and ERP results suggest that the attention disordered children have difficulty adjusting their level of physiological arousal, and are defective with respect to controlled (or effortful) processing.

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.

Coexistence of tics and hyperactivity in children: no additive at the psychophysiological level

The objective of the present work was to study the effects of tic disorder (TD) and hyperactivity (HA) on slow cortical potentials in children with combined TD + HA symptoms. Being related to different processes of frontal lobe control over preparatory cortical activity, early and late components of the slow negative potentials (eSNP, ISNP) were examined. SNP amplitude was analyzed as reflecting the sufficiency of preparatory cortical activation; scalp distribution of SNP and relationships to reaction times were studied as revealing the efficiency of task-related region-specific activation. It was hypothesized that if the effects of TD and HA were independent, additive effects on SNP amplitudes would be observed in children with coexisting TD and HA symptoms (TD + HA). Differences in SNP scalp distribution between control and patient groups were predicted to occur mainly over the frontal brain areas. Four groups of children (n = 10/11 in each group) were studied: healthy controls, pure TD, pure attention deficit hyperactivity disorder (ADHD), and combined tic and hyperactivity symptoms. SNPs were recorded in an auditory warned reaction time task (S1-S2-RT) from 8 electrode locations. According to the results, the effects of TD and HA on the sufficiency of task-dependent cortical activation were different, with only the TD factor related to lower SNP amplitudes. Nevertheless, deviant patterns of scalp distribution were found for pure ADHD patients, which suggested an inefficiency in involving the adequate task-related areas. For TD + HA children, like pure TD, lower SNP amplitudes and similar distribution and correlation patterns were present. Thus, according to amplitude, topography, and correlation criteria, TD + HA does not appear to be a subgroup of HA disorder but seems more similar to pure tic disorder.

Neurometrics, dynamic brain imaging and attention deficit hyperactivity disorder

OBJECTIVE

The literature on the development of frequency analysis of the electroencephalogram (neurometrics) and functional dynamic brain imaging techniques is reviewed. Clinical applications in the diagnosis and treatment of learning disorders of childhood are discussed.

CONCLUSIONS

While questions remain about the sensitivity and specificity of the neurometric method in diagnosing attention deficit hyperactivity disorder (ADHD), if the technique proved predictive of medication response, its importance would be established. However, evoked-potential studies, cerebral blood flow and cerebral glucose metabolic studies promise a better understanding of underlying psychological processes in ADHD.

BAEP studies in children with attention deficit disorder

Brainstem auditory evoked potentials (BAEPs) were performed on 114 children with attention deficit disorder (ADD). Prolonged latencies of waves III and V and longer brainstem transmission time interval of waves I-III and I-V were observed in the study group compared with normal controls. A significant asymmetry of wave III latency between the ears was found in children with ADD, but not observed in the control group. The authors conclude that children with ADD have brainstem dysfunction. BAEPs, an objective electrophysiological test, may contribute to the diagnosis of ADD, distinguishing these children from the normal population.

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.

Cognitive brain potential alterations in boys exposed to opiates: in utero and lifestyle comparisons

Several studies have observed that intrauterine exposure to opiates results in emotional and cognitive complications for the child, but genetic and postnatal social-environmental factors may also affect the CNS development of these children. To assess the relative contribution of the in utero and social-environmental (lifestyle) effects of opiate exposure, event-related potentials (ERPs) and performance were studied in three groups of 7- to 12-year-old boys: (1) the in utero/lifestyle group (IU/LS) contained 16 boys who were exposed to opiates (in utero and lived with opiate-abusing mothers, (2) the lifestyle group (LS) included 14 boys who lived with opiate-abusing mothers, and (3) the control group (CON) composed of 13 boys. The cognitive ERP components and task performance were recorded in the Auditory Rare Event Monitoring (AREM) task and the Sternberg Memory task (Sternberg, 1975). On the AREM and Sternberg Memory tasks, P200 component was significantly decreased for the IU/LS and LS groups. On the Sternberg Memory task, percent correct was also significantly impaired in IU/LS and LS groups. The ERP alterations in the boys living with opiate-abusing mothers with and without intrauterine opiate exposure were similar. A dysfunctional social environment may contribute to the cognitive deficits seen in the sons of opiate-abusing mothers.

Preferential neural processing of attended stimuli in attention-deficit hyperactivity disorder and normal boys

Event-related auditory and visual potentials were recorded from 36 attention-deficit hyperactivity disorder (ADHD) and 35 normal 6-year-old subjects engaged in a two-choice discrimination task. When normal subjects attended to stimuli in a given modality, enhanced negative (N2) and positive (P3b) responses (as compared with responses to nonattended stimuli) were found for auditory and visual target stimuli. In contrast, when ADHD subjects attended, little or no enhanced negative responses were found in either modality, and enhanced positive P3b responses were found only in response to visual target stimuli. Auditory N1, N2, and P3b and visual N2 amplitudes to attended target stimuli were significantly reduced in ADHD subjects as compared with normal subjects. No between-group differences were found for responses to nonattended stimuli. Both amplitude and latency abnormalities indicate that ADHD boys suffer from deficient preferential processing of attended stimuli. P3b and N2 abnormalities found here suggest deficiencies in two independent cognitive processes thought to be crucial to what we perceive, learn, and remember.

Information processing in children with minor neurological dysfunction: behavioural and neurophysiological indices

Minor neurological dysfunction (MND) refers to deviant function of the central nervous system in the absence of localizable neurological disorders. Children with no signs (n = 28) and with varying grades of MND (n = 48), classified according to failure on circumscript neurological subsystems, were administered selective and sustained attention tasks at the age of twelve. During the execution of one of the tasks, electrocortical activity of the brain was recorded at the Fz, Cz, Pz and Oz scalp locations. Of main interest were behavioural and electrophysiological indices of deficits in attentional control. With respect to the latter category, the investigation was focused on differences in event-related potential amplitudes reflecting subprocesses of cognitive processing (processing negativity, P300). Following a linear stage model of information processing, it was found that children who failed on three or more neurological subsystems (in particular on fine manipulation and coordination), exhibited deficits in the encoding, search and decision stages of processing. Furthermore, the children with MND showed a reduced positive parietal shift on target presentation. Under complex task conditions, children without MND showed a decrease in P300 amplitude which reflects the impact of processing negativity as a result of increased task demands; this effect was absent in children with MND. These electrocortical differences suggest imbalances in the external and internal neural regulation of the flow of information in the brain.

Prestimulation-induced startle modulation in attention-deficit hyperactivity disorder and nocturnal enuresis

Startle modulation was induced by prestimulation in 43, 6-11 year old boys with attention-deficit hyperactivity disorder (ADHD), 13 of whom were or had been enuretic, 17 age-matched enuretic boys, and 42 age-matched normal boys, using 60-ms and 120-ms prestimulation intervals and a 4000-ms continuous tone. There was a significant multivariate effect of enuresis on startle amplitude modulation. This effect was attributed primarily to the reduction of amplitude inhibition following the 120-ms prestimulation interval regardless of whether or not enuresis was associated with ADHD. There was no effect of ADHD on startle modulation by prestimulation. The inhibition following the 120-ms prestimulation interval in the enuretic boys was reduced to the level of 5-year-old normal children, suggesting a maturational component of the deficient startle inhibition. The neurophysiologic dysfunction underlying the deficient startle inhibition in enuresis, but not ADHD, is discussed in terms of a possible dysfunction of mesopontine reticular mechanisms mediating preattentive processing of signals associated with spinal reflexes involved in urinary bladder control.

Attention deficits in school-aged children and adolescents. Current issues and practice

Attention deficits in school-aged children and adolescents pose unique diagnostic and management challenges for the practitioner. While this symptom reflects a heterogeneous spectrum of disorders with varying etiologies, clinical manifestation, treatment needs, and outcomes, there are sufficient common attributes to enable identification and treatment. Accurate diagnosis relies on synthesis of information from history, rating scales, direct observations, and psychometric testing. Close attention must be paid to potential underlying or associated medical, processing, emotional, and psychosocial problems. Multimodal treatment is essential with close collaboration between the child, parents, and professionals. While there is a risk of negative outcomes if the symptoms are left unattended, many of these children also harbor strengths that need to be identified and nurtured.

An event-related potential study of controlled and automatic processes in 6-8-year-old boys with attention deficit hyperactivity disorder

Event-related potentials (ERPs) were recorded from 2 groups (attention deficit hyperactivity disorder (ADHD) and normal control) of 12 boys aged from 6 to 8 years. Subjects were submitted to 2 different types of categorization tasks (with rare targets and frequent standards) implying either the use of a verbal class or that of an ordered series. Each type of task was performed twice, the first with reading and the second without. Amplitudes and latencies of a fronto-central N150-P250 complex, a parieto-occipital N250-P350 complex and a parieto-occipital P500 were measured. Regardless of the task, hyperactive children showed larger fronto-central P250, larger parieto-occipital N250 and smaller parieto-occipital P350s and P500s; moreover, the latencies of their parieto-occipital P350s were shortened. When the categorization depended on the use of a verbal class, ERP reading effects were significantly smaller in hyperactives than in normal controls for the parieto-occipital waves only. Alternatively, the target effects were significantly larger in hyperactive children but for the fronto-central P250 only. These results suggest that in ADHD automatic processes were enhanced when higher-order controlled processes were inadequate.

Ontogeny of selective attention effects on event-related potentials in attention-deficit hyperactivity disorder and normal boys

A longitudinal study of young attention-deficit hyperactivity disorder (ADHD) boys has found clear evidence for developmental abnormalities in event-related potential (ERP) waves that reflect cognitive processes associated with selective attentional tasks. Boys alternated attention to auditory or visual modalities in a train of stimuli, in an attempt to detect target stimuli in the attended modality. Results suggest that ADHD boys' attentional difficulties are due to insufficient facilitation of responses to the attended stimuli and not to an inability to block ignored stimuli. Abnormalities in ERPs reflecting cognitive processes associated with both interchannel selection mechanisms (processing negativity) and intrachannel selection mechanisms (P3b) were found. The degree of abnormality in the P3b responses to target stimuli in ADHD boys (lower than normal boys) was found to increase with age. It is suggested that the abnormally low P36 response to attended target stimuli found in ADHD boys may be due in part to insufficient LC noradrenergic activity normally triggered by attended task-relevant or novel stimuli.

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.

[Evoked potentials and the mode of cognitive development in boys 6 to 8 years of age presenting hyperactivity with attention deficit]

Event-related potentials were recorded in 2 groups (attention deficit hyperactivity disorder--ADHD--and normal controls) of 12 male children aged between 6-8 years during 4 categorization tasks. Each task was performed with a different type of visual stimulus; pictures, words, geometrical figures or digits. The amplitudes and latencies of a fronto-central P250 and a parieto-occipital P350 were examined. The overall amplitude of the fronto-central P250 was larger in the ADHD group. However, the overall latency of the parieto-occipital P350 decreased with age; coincidentally, in the control group, the P350 latency measured in the left hemisphere became shorter with age for the words than for the pictures. This was not the case in the ADHD group. These results are discussed in relation to the level of the orienting reaction and the modes (general or differentiated) of cognitive development.