Parsing heterogeneity in attention-deficit hyperactivity disorder using EEG-based subgroups.

BACKGROUND: Attention-deficit/hyperactivity disorder (ADHD) is a heterogeneous condition for which multiple efforts to characterize brain state differences are underway. The objective of this study was to identify distinct subgroups of resting electroencephalography (EEG) profiles among children with and without ADHD and subsequently provide extensive clinical characterization of the subgroups. METHODS: Latent class analysis was used with resting state EEG recorded from a large sample of 781 children with and without ADHD (N = 620 ADHD, N = 161 Control), aged 6-18 years old. Behavioral and cognitive characteristics of the latent classes were derived from semistructured diagnostic interviews, parent completed behavior rating scales, and cognitive test performance. RESULTS: A five-class solution was the best fit for the data, of which four classes had a defining spectral power elevation. The distribution of ADHD and control subjects was similar across classes suggesting there is no one resting state EEG profile for children with or without ADHD. Specific latent classes demonstrated distinct behavioral and cognitive profiles. Those with elevated slow-wave activity (i.e. delta and theta band) had higher levels of externalizing behaviors and cognitive deficits. Latent subgroups with elevated alpha and beta power had higher levels of internalizing behaviors, emotion dysregulation, and intact cognitive functioning. CONCLUSIONS: There is population-level heterogeneity in resting state EEG subgroups, which are associated with distinct behavioral and cognitive profiles. EEG measures may be more useful biomarkers of ADHD outcome or treatment response rather than diagnosis.

A parietal biomarker for ADHD liability: as predicted by the distributed effects perspective model of ADHD.

BACKGROUND: We previously hypothesized that poor task-directed sensory information processing should be indexed by increased weighting of right hemisphere (RH) biased attention and visuo-perceptual brain functions during task operations and have demonstrated this phenotype in ADHD across multiple studies, using multiple methodologies. However, in our recent distributed effects model of ADHD, we surmised that this phenotype is not ADHD specific, but rather more broadly reflective of any circumstance that disrupts the induction and maintenance of an emergent task-directed neural architecture. Under this view, increased weighting of RH-biased attention and visuo-perceptual brain functions is expected to generally index neurocognitive sets that are not optimized for task-directed thought and action, and when durable expressed, liability for ADHD. METHOD: The current study tested this view by examining whether previously identified rightward parietal EEG asymmetry in ADHD was associated with common ADHD characteristics and comorbidities [i.e., ADHD risk factors (RFs)]. RESULTS: Barring one exception (non-right handedness), we found that it was. Rightward parietal asymmetry (RPA) was associated with carrying the DRD4-7R risk allele, being male, having mood disorder, and having anxiety disorder. However, differences in the specific expression of RPA were observed, which are discussed in relation to possible unique mechanisms underlying ADHD liability in different ADHD RFs. CONCLUSION: Rightward parietal asymmetry appears to be a durable feature of ADHD liability, as predicted by the Distributed Effects Perspective Model of ADHD. Moreover, variability in the expression of this phenotype may shed light on different sources of ADHD liability.

Community-Based Mindfulness Program for Disease Prevention and Health Promotion: Targeting Stress Reduction.

PURPOSE: Poorly managed stress leads to detrimental physical and psychological consequences that have implications for individual and community health. Evidence indicates that U.S. adults predominantly use unhealthy strategies for stress management. This study examines the impact of a community-based mindfulness training program on stress reduction. DESIGN: This study used a one-group pretest-posttest design. SETTING: The study took place at the UCLA Mindful Awareness Research Center in urban Los Angeles. SUBJECTS: A sample of N = 127 community residents (84% Caucasian, 74% female) were included in the study. INTERVENTION: Participants received mindfulness training through the Mindful Awareness Practices (MAPs) for Daily Living I. MEASURES: Mindfulness, self-compassion, and perceived stress were measured at baseline and postintervention. ANALYSIS: Paired-sample t-tests were used to test for changes in outcome measures from baseline to postintervention. Hierarchical regression analysis was fit to examine whether change in self-reported mindfulness and self-compassion predicted postintervention perceived stress scores. RESULTS: There were statistically significant improvements in self-reported mindfulness (t = -10.67, p < .001, d = .90), self-compassion (t = -8.50, p < .001, d = .62), and perceived stress (t = 9.28, p < .001, d = -.78) at postintervention. Change in self-compassion predicted postintervention perceived stress (ß = -.44, t = -5.06, p < .001), but change in mindfulness did not predict postintervention perceived stress (ß = -.04, t = -.41, p = .68). CONCLUSION: These results indicate that a community-based mindfulness training program can lead to reduced levels of psychological stress. Mindfulness training programs such as MAPs may offer a promising approach for general public health promotion through improving stress management in the urban community.

Randomised controlled pilot trial of mindfulness training for stress reduction during pregnancy.

This randomised controlled pilot trial tested a six-week mindfulness-based intervention in a sample of pregnant women experiencing high levels of perceived stress and pregnancy anxiety. Forty-seven women enrolled between 10 and 25 weeks gestation were randomly assigned to either a series of weekly Mindful Awareness Practices classes (n = 24) with home practice or to a reading control condition (n = 23). Hierarchical linear models of between-group differences in change over time demonstrated that participants in the mindfulness intervention experienced larger decreases from pre-to post-intervention in pregnancy-specific anxiety and pregnancy-related anxiety (PRA) than participants in the reading control condition. However, these effects were not sustained through follow-up at six weeks post-intervention. Participants in both groups experienced increased mindfulness, as well as decreased perceived stress and state anxiety over the course of the intervention and follow-up periods. This study is one of the first randomised controlled pilot trials of a mindfulness meditation intervention during pregnancy and provides some evidence that mindfulness training during pregnancy may effectively reduce PRA and worry. We discuss some of the dilemmas in pursuing this translational strategy and offer suggestions for researchers interested in conducting mind-body interventions during pregnancy.

Characterization of the theta to beta ratio in ADHD: identifying potential sources of heterogeneity.

OBJECTIVE: The goal of this study is to characterize the theta to beta ratio (THBR) obtained from electroencephalogram (EEG) measures, in a large sample of community and clinical participants with regard to (a) ADHD diagnosis and subtypes, (b) common psychiatric comorbidities, and (c) cognitive correlates. METHOD: The sample includes 871 participants (595 youth and 276 adults) with and without ADHD. All participants underwent extensive assessment, including semistructured diagnostic interviews, cognitive testing, and EEG recording. RESULTS: The THBR did not differ significantly by ADHD status for youth but was significantly lower in adults with ADHD compared with controls. ADHD subtype and psychiatric comorbidities such as disruptive behavior disorders and depression have opposing and significant mediating effects on the THBR. CONCLUSION: The THBR is affected by several mediating factors associated with ADHD such as ADHD subtype and psychiatric comorbidity. More research is needed to understand the functional significance of the THBR in ADHD.

Brain growth rate abnormalities visualized in adolescents with autism.

Autism spectrum disorder is a heterogeneous disorder of brain development with wide ranging cognitive deficits. Typically diagnosed before age 3, autism spectrum disorder is behaviorally defined but patients are thought to have protracted alterations in brain maturation. With longitudinal magnetic resonance imaging (MRI), we mapped an anomalous developmental trajectory of the brains of autistic compared with those of typically developing children and adolescents. Using tensor-based morphometry, we created 3D maps visualizing regional tissue growth rates based on longitudinal brain MRI scans of 13 autistic and seven typically developing boys (mean age/interscan interval: autism 12.0 ± 2.3 years/2.9 ± 0.9 years; control 12.3 ± 2.4/2.8 ± 0.8). The typically developing boys demonstrated strong whole brain white matter growth during this period, but the autistic boys showed abnormally slowed white matter development (P = 0.03, corrected), especially in the parietal (P = 0.008), temporal (P = 0.03), and occipital lobes (P = 0.02). We also visualized abnormal overgrowth in autism in gray matter structures such as the putamen and anterior cingulate cortex. Our findings reveal aberrant growth rates in brain regions implicated in social impairment, communication deficits and repetitive behaviors in autism, suggesting that growth rate abnormalities persist into adolescence. Tensor-based morphometry revealed persisting growth rate anomalies long after diagnosis, which has implications for evaluation of therapeutic effects.

Sex-specific influence of DRD2 on ADHD-type temperament in a large population-based birth cohort.

Attention-deficit/hyperactivity disorder (ADHD) is a childhood-onset neurodevelopmental disorder with a significant public-health impact. Previously, we described a candidate gene study in a population-based birth cohort that demonstrated an association with ADHD-affected males and the dopamine receptor D2 (DRD2). The current study evaluates potential associations of dopamine receptor genes and Cloninger temperament traits within this same sample. Participants with stringent lifetime ADHD diagnoses were ascertained systematically from the genetically isolated Northern Finland 1986 Birth Cohort (n=9432), resulting in 178 cases and 157 controls. Markers in all known dopamine receptor genes were genotyped. We report an association of DRD2 with low Persistence in females (rs1079727 P=0.02, rs1124491 P=0.02, rs1800497 P=0.03). The associated DRD2 minor allelic haplotype (CAA, P=0.03) is the same haplotype we previously associated with ADHD in males in this birth cohort. The current study further supports previous results on the role of DRD2 in individuals with ADHD. Investigations suggest that DRD2 may have an impact on both males and females, but the particular outcome appears sex-specific, manifesting as ADHD in males and low Persistence in females. Furthermore, these findings suggest that the putative role of low Persistence as an endophenotype for ADHD deserves further investigation.

Genome-wide association study of intelligence: additive effects of novel brain expressed genes.

OBJECTIVE: The purpose of the present study was to identify common genetic variants that are associated with human intelligence or general cognitive ability. METHOD: We performed a genome-wide association analysis with a dense set of 1 million single-nucleotide polymorphisms (SNPs) and quantitative intelligence scores within an ancestrally homogeneous family sample of 656 individuals with at least one child affected by attention-deficit/hyperactivity disorder (ADHD). RESULTS: Haplotype trend regression analysis with sliding four-SNP windows identified haplotypes of genome-wide significance in genes involved in synaptic signaling (KIF16B; p = 1.27E-08) and neurodevelopment (PAX5; p = 3.58E-08), and highlight findings from a recent genetic study of cognitive ability (RXRA; p = 7.7E-08; GYPC; p = 2.5E-07). Further interrogation of SNPs within top haplotypes reveals that the minor alleles are associated with higher intelligence, whereas others are associated with relatively lower (but still average range) intelligence. Effects of the eight genes are additive, as a greater number of the associated genotypes in a given individual predict higher intelligence (p = 5.36E-08) and account for 8% of variance in intelligence. CONCLUSIONS: Analyses that examine additive genetic effects may be useful in identifying regions where the additive effects of SNPs have a significant effect on phenotype. These results describe novel variants and additive effects of genes involved in brain development on variability in intelligence within an ADHD sample. The precise mechanisms of these loci in relation to determining individual differences in general cognitive ability require further investigation.

Genome-wide analysis of copy number variants in attention deficit hyperactivity disorder: the role of rare variants and duplications at 15q13.3.

OBJECTIVE: Attention deficit hyperactivity disorder (ADHD) is a common, highly heritable psychiatric disorder. Because of its multifactorial etiology, however, identifying the genes involved has been difficult. The authors followed up on recent findings suggesting that rare copy number variants (CNVs) may be important for ADHD etiology. METHOD: The authors performed a genome-wide analysis of large, rare CNVs (<1% population frequency) in children with ADHD (N=896) and comparison subjects (N=2,455) from the IMAGE II Consortium. RESULTS: The authors observed 1,562 individually rare CNVs >100 kb in size, which segregated into 912 independent loci. Overall, the rate of rare CNVs >100 kb was 1.15 times higher in ADHD case subjects relative to comparison subjects, with duplications spanning known genes showing a 1.2-fold enrichment. In accordance with a previous study, rare CNVs >500 kb showed the greatest enrichment (1.28-fold). CNVs identified in ADHD case subjects were significantly enriched for loci implicated in autism and in schizophrenia. Duplications spanning the CHRNA7 gene at chromosome 15q13.3 were associated with ADHD in single-locus analysis. This finding was consistently replicated in an additional 2,242 ADHD case subjects and 8,552 comparison subjects from four independent cohorts from the United Kingdom, the United States, and Canada. Presence of the duplication at 15q13.3 appeared to be associated with comorbid conduct disorder. CONCLUSIONS: These findings support the enrichment of large, rare CNVs in ADHD and implicate duplications at 15q13.3 as a novel risk factor for ADHD. With a frequency of 0.6% in the populations investigated and a relatively large effect size (odds ratio=2.22, 95% confidence interval=1.5­3.6), this locus could be an important contributor to ADHD etiology.

Genome-wide copy number variation study associates metabotropic glutamate receptor gene networks with attention deficit hyperactivity disorder.

Attention deficit hyperactivity disorder (ADHD) is a common, heritable neuropsychiatric disorder of unknown etiology. We performed a whole-genome copy number variation (CNV) study on 1,013 cases with ADHD and 4,105 healthy children of European ancestry using 550,000 SNPs. We evaluated statistically significant findings in multiple independent cohorts, with a total of 2,493 cases with ADHD and 9,222 controls of European ancestry, using matched platforms. CNVs affecting metabotropic glutamate receptor genes were enriched across all cohorts (P = 2.1 × 10(-9)). We saw GRM5 (encoding glutamate receptor, metabotropic 5) deletions in ten cases and one control (P = 1.36 × 10(-6)). We saw GRM7 deletions in six cases, and we saw GRM8 deletions in eight cases and no controls. GRM1 was duplicated in eight cases. We experimentally validated the observed variants using quantitative RT-PCR. A gene network analysis showed that genes interacting with the genes in the GRM family are enriched for CNVs in ∼10% of the cases (P = 4.38 × 10(-10)) after correction for occurrence in the controls. We identified rare recurrent CNVs affecting glutamatergic neurotransmission genes that were overrepresented in multiple ADHD cohorts.

Atypical EEG beta asymmetry in adults with ADHD.

BACKGROUND: Abnormal brain laterality (ABL) is well established in ADHD. However, its clinical specificity and association to cognitive and clinical symptoms is not yet understood. Previous studies indicate increased right hemisphere (RH) contribution in both ADHD and reading impaired samples. The current study investigates whether this ABL characteristic occurs in adults with ADHD absent comorbid language impairment. METHODS: EEG beta asymmetry was compared in 35 adult ADHD subjects and 104 controls during rest and active cognition. Group differences in beta asymmetry were then further evaluated for association to linguistic and attentional abilities, as well as association to beta asymmetry measures across different brain regions. RESULTS: Adults with ADHD showed pronounced rightward beta asymmetry (p=.00001) in inferior parietal regions (P8-P7) during a continuous performance task (CPT) that could not be attributed to linguistic ability. Among ADHD subjects only, greater rightward beta asymmetry at this measure was correlated with better CPT performance. Furthermore, this measure showed a lack of normal association (i.e., observed in controls) to left-biased processing in temporal-parietal (TP8-TP7) brain regions important for higher order language functions. CONCLUSION: Adult ADHD involves abnormally increased right-biased contribution to CPT processing that could not be attributed to poor language ability. This appears to also involve abnormal recruitment of LH linguistic processing regions and represents an alternative, albeit less effective, CPT processing strategy. These findings suggest different pathophysiologic mechanisms likely underlie RH biased processing in ADHD and reading impaired samples.

Familial clustering and DRD4 effects on electroencephalogram measures in multiplex families with attention deficit/hyperactivity disorder.

OBJECTIVE: The current study tests electroencephalogram (EEG) measures as a potential endophenotype for attention deficit/hyperactivity disorder (ADHD) by examining sibling and parent-offspring similarity, familial clustering with the disorder, and association with the dopamine receptor D4 (DRD4) candidate gene. METHOD: The sample consists of 531 participants (191 parents and 340 children) from 132 multiplex families with ADHD who participated in a larger genetics study. All members of the families underwent extensive assessment including semi-structured diagnostic interviews and EEG recording. RESULTS: Strong sibling similarity and parent-offspring correlations in EEG power emerged, suggesting high trait heritability. Increased theta power was observed among children with ADHD when compared with unaffected children, and there were no differences according to ADHD subtype. Within the parent sample, ADHD diagnostic status and ADHD subtype group differences emerged in the theta, alpha, and beta frequency bands. DRD4 effects for both parents and children were apparent in the beta frequency band and for children only in the theta frequency band. CONCLUSIONS: This study suggests that EEG measures are a promising avenue of study in the search for putative endophenotypes for ADHD, and that variability at the DRD4 gene may contribute to this endophenotype.

On genome-wide association studies for family-based designs: an integrative analysis approach combining ascertained family samples with unselected controls.

Large numbers of control individuals with genome-wide genotype data are now available through various databases. These controls are regularly used in case-control genome-wide association studies (GWAS) to increase the statistical power. Controls are often "unselected" for the disease of interest and are not matched to cases in terms of confounding factors, making the studies more vulnerable to confounding as a result of population stratification. In this communication, we demonstrate that family-based designs can integrate unselected controls from other studies into the analysis without compromising the robustness of family-based designs against genetic confounding. The result is a hybrid case-control family-based analysis that achieves higher power levels than population-based studies with the same number of cases and controls. This strategy is widely applicable and works ideally for all situations in which both family and case-control data are available. The approach consists of three steps. First, we perform a standard family-based association test that does not utilize the between-family component. Second, we use the between-family information in conjunction with the genotypes from unselected controls in a Cochran-Armitage trend test. The p values from this step are then calculated by rank ordering the individual Cochran-Armitage trend test statistics for the genotype markers. Third, we generate a combined p value with the association p values from the first two steps. Simulation studies are used to assess the achievable power levels of this method compared to standard analysis approaches. We illustrate the approach by an application to a GWAS of attention deficit hyperactivity disorder parent-offspring trios and publicly available controls.

ADHD familial loading and abnormal EEG alpha asymmetry in children with ADHD.

OBJECTIVE: Abnormal brain laterality (ABL) is indicated in ADHD. ADHD and brain laterality are heritable. Genetic factors contributing to lateralization of brain function may contribute to ADHD. If so, increased ADHD family loading should be associated with greater ABL. Previous studies have shown increased rightward alpha asymmetry in ADHD. We tested whether this was more pronounced in ADHD children with increased ADHD family loading. METHODS: We compared EEG alpha asymmetry at rest and during the Conner's Continuous Performance Test (CPT) in ADHD children with and without ADHD affected parents, and replicated our findings in a second larger sample. The replication study additionally stratified the parent-affected sample by parental persistent versus non-persistent ADHD status, increased spatial resolution of EEG measures, and assessed low versus high-alpha. RESULTS: Study-1: the parent-affected group showed increased rightward asymmetry across frontal and central regions and reduced rightward parietal asymmetry during an eyes closed (EC) condition, as well as increasing rightward parietal asymmetry with advancing age during the CPT. Study-2 replicated these findings and further delineated influences of low versus high-alpha, recording site, and effects of parental persistent versus non-persistent ADHD status. CONCLUSION: Increased ADHD familial loading was associated with increased rightward frontal asymmetry. In contrast, increased rightward parietal asymmetry was associated with reduced ADHD family loading. Frontal results are consistent with an ADHD endophenotype. Parietal results suggest an ADHD adaptive trait prevalent with less ADHD family loading. Age effects indicate a unique developmental course among ADHD children whose parents have non-persistent ADHD.

A candidate gene analysis of methylphenidate response in attention-deficit/hyperactivity disorder.

OBJECTIVE: This study examines the potential role of candidate genes in moderating treatment effects of methylphenidate (MPH) in attention-deficit/hyperactivity disorder (ADHD). METHOD: Eighty-two subjects with ADHD aged 6 to 17 years participated in a prospective, double-blind, placebo-controlled, multiple-dose, crossover titration trial of immediate release MPH three times daily. The subjects were assessed on a variety of parent and clinician ratings and a laboratory math test. Data reduction based on principal components analysis identified statistically derived efficacy and side effect outcomes. RESULTS: Attention-deficit/hyperactivity disorder symptom response was predicted by polymorphisms at the serotonin transporter (SLC6A4) intron 2 VNTR (p = .01), with a suggested trend for catechol-O-methyltransferase (COMT) (p = .04). Gene × dose interactions were noted on math test outcomes for the dopamine D4 receptor (DRD4) promoter (p = .008), DRD4 exon 3 VNTR (p = .006), and SLC6A4 promoter insertion/deletion polymorphism (5HTTLPR) (p = .02). Irritability was predicted by COMT (p = .02). Vegetative symptoms were predicted by 5HTTLPR (p = .003). No significant effects were noted for the dopamine transporter (SLC6A3) or synaptosomal-associated protein 25 (SNAP25). CONCLUSIONS: This article confirms and expands previous studies suggesting that genes moderate ADHD treatment response. The ADHD outcomes are not unitary but reflect both behavioral and learning domains that are likely influenced by different genes. Future research should emphasize candidate gene and genome-wide association studies in larger samples, symptom reduction as well as side effects outcomes, and responses over full therapeutic dose ranges to assess differences in both gene and gene × dose interactive effects.

Mindfulness and attention deficit hyperactivity disorder.

Attention deficit hyperactivity disorder (ADHD) is a disorder characterized by attentional difficulties. Mindfulness is a receptive attention to present experience. Both ADHD and mindfulness are associated with attention and personality. This study tests whether individuals with ADHD have lower mindfulness scores than controls and, if true, whether personality contributes to these differences. One hundred and five adults (half with ADHD) were assessed for mindfulness, using the Kentucky Inventory of Mindfulness Skills, and personality, using the Tridimensional Character Inventory. Individuals with ADHD report themselves as less mindful than non-ADHD controls and more novelty-seeking, less self-directed, and more self-transcendent. Mindfulness is negatively associated with ADHD and positively associated with self-directedness and self-transcendence. Analyses of subscales of mindfulness suggest that ADHD is associated most with the "Acting in Awareness" dimension, perhaps because of shared items reflecting attentional variability. The current findings support that a large portion of variability in trait mindfulness can be explained by ADHD status and personality traits of self-directedness and self-transcendence. It further suggests that interventions that increase mindfulness might improve symptoms of ADHD and increase self-directedness and/or self-transcendence.

Social functioning difficulties in ADHD: association with PDD risk.

Although social difficulties are a common feature of Attention-Deficit Hyperactivity Disorder (ADHD), little is known about the diversity of social problems, their etiology, or their relationship to disorders of social behavior, such as autism or Pervasive Developmental Disorder (PDD). In 379 children and adolescents with ADHD, social functioning was assessed using the Child Behavior Checklist (Achenbach, 1991). Factor analysis and structural equation modeling revealed two factors that we labeled Peer Rejection and Social Immaturity. A factor reflecting ;PDD risk' was defined from eight items of a separate screening instrument for PDD and examined for its association with these two social factors. There was a significant association with both factors, but the association was much stronger for the Social Immaturity (Standardized Beta [beta ] = .51) than Peer Rejection (beta = .29) factors. Social Immaturity was also associated with a greater number of hyperactive symptoms while high Peer Rejection was associated with increased aggression and lower IQ in the ADHD children.

Atypical alpha asymmetry in adults with ADHD.

INTRODUCTION: A growing body of literature suggests atypical cerebral asymmetry and interhemispheric interaction in ADHD. A common means of assessing lateralized brain function in clinical populations has been to examine the relative proportion of EEG alpha activity (8-12 Hz) in each hemisphere (i.e., alpha asymmetry). Increased rightward alpha asymmetry has been associated with ADHD-like traits such as reduced reward responsiveness, a lack of inhibition toward aversive experience, and increased approach behaviors, and previous work has indicated increased rightward alpha asymmetry in children with ADHD. The current study explores whether increased rightward alpha asymmetry is also evident in adults with ADHD. METHOD: We assessed low (8-10 Hz) and high (10-12 Hz) alpha asymmetry in adults with ADHD (n=29) versus controls (n=62) during baseline and cognitive activation conditions for nine homologous electrode pairs along the anterior-posterior axis. RESULT: Seven results emerged (p<.05) showing increased rightward alpha asymmetry in adults with ADHD. This occurred in three specific electrode pairs across two testing conditions, and five of six results occurred in the lower alpha band. Finally, post hoc analysis indicated that increased rightward alpha asymmetry was generally associated with greater numbers of ADHD symptoms--with a possible parietal association for inattentive and a fronto-temporal association for hyperactivity symptoms. CONCLUSIONS: Increased rightward alpha asymmetry previously observed in children with ADHD appears to be a developmentally persistent feature of ADHD.

Cortical activity patterns in ADHD during arousal, activation and sustained attention.

OBJECTIVE: The goal of the present study is to test whether there are Attention-Deficit Hyperactivity Disorder (ADHD)-related differences in brain electrical activity patterns across arousal, activation and vigilance states. METHOD: The sample consists of 80 adults (38 with ADHD and 42 non-ADHD controls) who were recruited for a family study on the genetics of ADHD. Patterns of cortical activity were measured using electroencephalography (EEG) during baseline and sustained attention conditions and compared according to ADHD diagnostic status. Cortical activity was examined separately for the first, middle, and last 5-min of the sustained attention task to assess whether patterns differed over time and according to ADHD status. RESULTS: In frontal and parietal regions, patterns of activation in the alpha (8-10 Hz) range differed according to ADHD status, indicating increased cortical arousal among ADHD subjects. Beta power (13-14 and 17-18 Hz) also differed between ADHD and controls, indicating increased cortical activation is associated with ADHD. Behavioral performance on the sustained attention task did not differ significantly by diagnosis. EEG correlates of cognitive performance differed significantly ADHD diagnosis and were primarily in frontal regions. Brain activation patterns recorded during the sustained attention task suggest that the ADHD group exhibited significantly increased cortical activation at the end of the task when compared to controls. CONCLUSIONS: Adults with ADHD may have different neural organization primarily in frontal regions which results in the need for continually high levels of cortical activation to maintain sustained attention.

Rethinking a right hemisphere deficit in ADHD.

INTRODUCTION: Early observations from lesion studies suggested right hemisphere (RH) dysfunction in ADHD. However, a strictly right-lateralized deficit has not been well supported. An alternatively view suggests increased R > L asymmetry of brain function and abnormal interhemispheric interaction. If true, RH pathology in ADHD should reflect interhemispherically networked and overactivated functioning. The authors evaluated these assertions. METHOD: Four elements of lateralized brain function were measured: LH specialized, RH specialized, LH with interhemispheric processing (LH/IH), and RH with interhemispheric processing (RH/IH). Next, the authors tested their association with cognitive ability, psychiatric comorbidity, and sibling correlations in 79 children with ADHD. RESULTS: RH/IH processing was uniquely associated with other outcome measures. There were no associations for independent RH or LH function alone. CONCLUSION: Interhemispherically networked RH processing is critical in ADHD. In addition, lack of association between LH specialized processing and cognitive ability (especially for verbal cognitive tasks) supports increased RH mediation of task processing.