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Journal of Attention Disorders 12/2012; · 2.45 Impact Factor
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ABSTRACT: 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.
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.
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.
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.
Neuropsychologia 10/2010; 48(12):3532-9. · 3.64 Impact Factor
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ABSTRACT: 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.
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.
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.
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.
Journal of psychiatric research 12/2009; 44(9):605-15. · 3.72 Impact Factor
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ABSTRACT: 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.
Journal of Clinical Psychology 09/2009; 65(10):1087-98. · 2.12 Impact Factor
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ABSTRACT: 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.
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.
Increased rightward alpha asymmetry previously observed in children with ADHD appears to be a developmentally persistent feature of ADHD.
Neuropsychologia 08/2009; 47(10):2082-8. · 3.64 Impact Factor
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ABSTRACT: 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.
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.
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.
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.
Neuropsychologia 05/2009; 47(10):2114-9. · 3.64 Impact Factor
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ABSTRACT: 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.
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.
RH/IH processing was uniquely associated with other outcome measures. There were no associations for independent RH or LH function alone.
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.
Journal of Attention Disorders 09/2008; 13(1):3-17. · 2.45 Impact Factor
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ABSTRACT: ADHD is a childhood-onset psychiatric condition that often continues into adulthood. Stimulant medications are the mainstay of treatment; however, additional approaches are frequently desired. In recent years, mindfulness meditation has been proposed to improve attention, reduce stress, and improve mood. This study tests the feasibility of an 8-week mindfulness training program for adults and adolescents with ADHD.
Twenty-four adults and eight adolescents with ADHD enrolled in a feasibility study of an 8-week mindfulness training program.
The majority of participants completed the training and reported high satisfaction with the training. Pre-post improvements in self-reported ADHD symptoms and test performance on tasks measuring attention and cognitive inhibition were noted. Improvements in anxiety and depressive symptoms were also observed.
Mindfulness training is a feasible intervention in a subset of ADHD adults and adolescents and may improve behavioral and neurocognitive impairments. A controlled clinical study is warranted.
Journal of Attention Disorders 06/2008; 11(6):737-46. · 2.45 Impact Factor
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ABSTRACT: Executive dysfunction in ADHD is well supported. However, recent studies suggest that more fundamental impairments may be contributing. We assessed brain function in adults with ADHD during simple and complex forms of processing.
We used functional magnetic resonance imaging with forward and backward digit spans to investigate number repetitions and complex working memory function. If pathology is limited to higher cognitive operations, group differences should be confined to the backward condition.
During the forward digit span, ADHD participants exhibited greater activation of LH linguistic processing areas and increased activation of right frontal and parietal cortices. During the backward digit span, they exhibited greater activation of LH linguistic processing areas and failed to activate bilateral parietal regions important for the complex executive operations.
Abnormal brain function among adult ADHD participants was not limited to complex executive functions. Abnormal processing of numeric stimuli was indicated during both simple and complex cognitive operations.
Journal of Attention Disorders 10/2007; 11(2):125-40. · 2.45 Impact Factor
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ABSTRACT: Few studies directly examined the nature of hemispheric specialization and interaction in ADHD. The present experiment investigated left/right brain dynamics in unmedicated right handed adults with ADHD (n = 19) and in controls (n = 19), using a dichotic listening task to assess hemispheric differences in word and emotion recognition. We also assessed how focusing attention on a single ear modulated lateralized performance and affected cross-callosal interference effects. Analysis of variance indicated that ADHD subjects showed reduced left hemisphere specialization, were better at processing emotions, and worse at processing words compared to controls. These differences were eliminated during focused attention. Finally, during presumed right hemisphere processing of linguistic stimuli, subjects with ADHD showed reduced left hemisphere interference. We concluded that ADHD subjects demonstrated greater right hemisphere and reduced left hemisphere contribution during this task relative to controls. We posit that these hemispheric differences were due to management or use of available cognitive resources rather than inherent capacity.
Neuropsychologia 02/2006; 44(6):896-904. · 3.64 Impact Factor
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ABSTRACT: Introduction: cognitive/behavioral testing, structural imaging, and functional imaging, has demonstrated atypical cerebral asymmetries in patients with attention-deficit/hyperactivity disorder (ADHD). However, few studies directly examined the nature of hemispheric specialization and interaction in this population. Methods: the present experiment applied techniques from behavioral laterality research to assess directly left/right brain dynamics in unmedicated adults with ADHD (n=21) and controls (n=22). We used a lateralized lexical decision task to assess hemispheric differences in word recognition and cross-callosal interhemispheric transfer of linguistic information. Results: analysis of variance indicated that ADHD subjects were impaired relative to controls in identifying words in both hemispheres (P=0.001). Furthermore, ADHD subjects exhibited decreased effects for ‘word regularity’ (P=004), enhanced effects of ‘word frequency’ (P=007), and an increased bias for ‘nonword’ responses overall (P=03), as well as during left visual field trials in particular (P=01). Conclusions: adult subjects with ADHD demonstrated poor linguistic processing. Group differences in sensitivity to semantic and phonological linguistic variables, along with differences in response biases, suggested that ADHD subjects had reduced left hemisphere and enhanced right hemisphere involvement during our task. These findings are relevant to current research investigating ‘endophenotypes’ in ADHD, as laterality indices may prove useful in etiological research, particularly molecular genetic investigations, and highlights the relevance of brain laterality research in clinical psychiatry.
Clinical Neuroscience Research.
