The influence of methylphenidate on the power spectrum of ADHD children - an MEG study

Power Spectrum and Connectivity Analysis in EEG Recording during Attention and Creativity Performance in Children

The present research aims at examining the power spectrum and exploring functional brain connectivity/disconnectivity during concentration performance, as measured by the d2 test of attention and creativity as measured by the CREA test in typically developing children. To this end, we examined brain connectivity by using phase synchrony (i.e., phase locking index (PLI) over the EEG signals acquired by the Emotiv EPOC neuroheadset in 15 children aged 9- to 12-years. Besides, as a complement, a power spectrum analysis of the acquired signals was performed. Our results indicated that, during d2 Test performance there was an increase in global gamma phase synchronization and there was a global alpha and theta band desynchronization. Conversely, during CREA task, power spectrum analysis showed a significant increase in the delta, beta, theta, and gamma bands. Connectivity analysis revealed marked synchronization in theta, alpha, and gamma. These findings are consistent with other neuroscience research indicating that multiple brain mechanisms are indeed involved in creativity. In addition, these results have important implications for the assessment of attention functions and creativity in clinical and research settings, as well as for neurofeedback interventions in children with typical and atypical development.

Fish oil supplementation may improve attention, working memory and attention-deficit/hyperactivity disorder symptoms in adults with autism spectrum disorder: a randomised crossover trial

Marine n-3 fatty acids (n-3LCPUFA) have shown neurocognitive benefits in children with attention-deficit/hyperactivity disorder (ADHD), but few trials have examined effects in adults with autism spectrum disorder (ASD). We explored, if n-3LCPUFA affect cognitive functions in adults with ASD, and if effects are modified by comorbid ADHD. In a 2 × 4 week crossover study, twenty-six participants were randomised to sequence of supplementation with fish oil (FO, 5·2 g/d n-3PUFA) and safflower oil (SO). At baseline and after each period, we measured primary outcomes: attention (d2-test) and spatial working memory (Corsi test) and secondary outcomes: flexibility (Stroop word-colour test), ADHD symptoms (Conners scales), executive functions (Behavioural Inventory of Executive Function) and social behaviour (Social Responsiveness Scale). The dropout rate was 15 %. Compliance was 94 % and correlated with whole-blood n-3LCPUFA. Corsi scores improved by ∼0·3 × sd (P = 0·032) after FO v. SO, and the odds for d2 errors were 30 % lower (P = 0·016), which was supported by improved Conners scores of attention (P = 0·023). Improvement in Conners ADHD symptom score was limited to participants with ADHD (-3·5(-6·0; -1·0), n 10 v. -0·2(-2·5;2·2), n 11 without ADHD, Pinteraction = 0·096), who also improved their behavioural regulation index by 0·3 × sd after FO (Pinteraction = 0·016). Participants without ADHD gained most in d2 test performance (OR = 0·4(0·2;0·7) v. 0·9(0·6;1·3) in those with ADHD, Pinteraction = 0·002), but their executive function score was exacerbated after FO (5·9(0·0,11·8), Pinteraction = 0·039). Our results did not show any effects on ASD symptoms, but suggest that FO may improve attention and working memory in adults with ASD and ameliorate ADHD symptoms in those with comorbid ADHD.

Convergent validity, academic correlates and age- and SES-based normative data for the d2 Test of attention in children

The d2, test of attention is one of the most used neuropsychological tests to measure attention in clinical and research settings. To date, no studies have examined neither its convergent and divergent validity in children nor its relationship with academic skills at school age. The aims of the present study were: (1) to examine the convergent and divergent validity of the d2 Test in a non-clinical pediatric population, (2) to explore the relationship between d2 task performance and academic skills (i.e., math, reading and writing abilities) and (3) to develop normative data for Spanish-speaking children (n = 360 8- to 12-year-old children) stratified by age and socioeconomic status (SES). Pearson's correlation and Structural Equation Models (SEM) were used to analyze the d2 Test validity and its relationship with academic skills. A between-subjects factorial MANOVA was used to examine differences among SES (Middle, Low), age (8-10, 11-12), and sex (male, female). Findings revealed a significant relationship between d2 task performance and all attention and executive functions (EF) measures under analysis providing evidence of good convergent validity. Furthermore, SEM results showed that attention has direct effects on math and reading and writing skills. Finally, our study confirms the influence of age and SES on d2 task performance and provides normative data for middle- and low-SES children. These results have important implications for the assessment of attention functions in clinical and research settings in children with typical and atypical development.

Differences in Resting-state Quantitative Electroencephalography Patterns in Attention Deficit/Hyperactivity Disorder with or without Comorbid Symptoms

Objective

The aim of the present study was to evaluate the role of comorbid psychiatric symptoms on quantitative electroencephalogram (QEEG) activities in boys with the attention deficit/hyperactivity disorder (ADHD).

Methods

All participants were male students in the second, third or fourth grade in elementary school. Therefore, there were no significant differences in age or sex. Participants with ADHD were assigned to one of three groups: pure ADHD (n=22), ADHD with depressive symptoms (n=11), or ADHD with problematic internet use (n=19). The Korean version of the Children’s Depression Inventory and the Korean Internet Addiction Self-scale were used to assess depressive symptoms and problematic internet use, respectively. Resting-state EEG during eyes closed was recorded, and the absolute power of five frequency bands was analyzed: delta (1–4 Hz), theta (4–8 Hz), alpha (8–12 Hz), beta (12–30 Hz), and gamma (30–50 Hz).

Results

The ADHD with problematic internet use group showed decreased absolute theta power at the central and posterior region compared with the pure ADHD group. However, The ADHD with depressive symptoms group showed no significant differences compared with the other groups.

Conclusion

These findings will contribute to a better understanding of brain-based electrophysiological changes in children with ADHD in accordance with comorbid psychiatric symptoms.

Transcranial Electric Stimulation for Precision Medicine: A Spatiomechanistic Framework

During recent years, non-invasive brain stimulation, including transcranial electrical stimulation (tES) in general, and transcranial direct current stimulation (tDCS) in particular, have created new hopes for treatment of neurological and psychiatric diseases. Despite promising primary results in some brain disorders, a more widespread application of tES is hindered by the unsolved question of determining optimum stimulation protocols to receive meaningful therapeutic effects. tES has a large parameter space including various montages and stimulation parameters. Moreover, inter- and intra-individual differences in responding to stimulation protocols have to be taken into account. These factors contribute to the complexity of selecting potentially effective protocols for each disorder, different clusters of each disorder, and even each single patient. Expanding knowledge in different dimensions of basic and clinical neuroscience could help researchers and clinicians to select potentially effective protocols based on tES modulatory mechanisms for future clinical studies. In this article, we propose a heuristic spatiomechanistic framework which contains nine levels to address tES effects on brain functions. Three levels refer to the spatial resolution (local, small-scale networks and large-scale networks) and three levels of tES modulatory effects based on its mechanisms of action (neurochemical, neuroelectrical and oscillatory modulations). At the group level, this framework could be helpful to enable an informed and systematic exploration of various possible protocols for targeting a brain disorder or its neuroscience-based clusters. Considering recent advances in exploration of neurodiversity at the individual level with different brain mapping technologies, the proposed framework might also be used in combination with personal data to design individualized protocols for tES in the context of precision medicine in the future.

tES Stimulation as a Tool to Investigate Cognitive Processes in Healthy Individuals

Abstract. This paper is aimed at providing an introduction to up-to-date noninvasive brain stimulation tools that have been successful in modulating higher-level cognitive functions in healthy individuals. The current review focuses on transcranial electrical stimulation (tES) studies aiming to explore cognitive models from an experimental rather than clinical viewpoint. It focuses primarily on major advances in language, working memory, learning, response inhibition, and other executive functions in healthy individuals, and the use of different methods of electrical brain stimulation such as transcranial direct current stimulation (tDCS), transcranial alternating current stimulation (tACS), and transcranial random noise stimulation (tRNS). The final section summarizes the scientific novelty of the reviewed papers and discusses the possible roles of brain stimulation in future experimental research and clinical applications.

Test-retest reliability of resting-state magnetoencephalography power in sensor and source space

Several studies have reported changes in spontaneous brain rhythms that could be used as clinical biomarkers or in the evaluation of neuropsychological and drug treatments in longitudinal studies using magnetoencephalography (MEG). There is an increasing necessity to use these measures in early diagnosis and pathology progression; however, there is a lack of studies addressing how reliable they are. Here, we provide the first test-retest reliability estimate of MEG power in resting-state at sensor and source space. In this study, we recorded 3 sessions of resting-state MEG activity from 24 healthy subjects with an interval of a week between each session. Power values were estimated at sensor and source space with beamforming for classical frequency bands: delta (2-4 Hz), theta (4-8 Hz), alpha (8-13 Hz), low beta (13-20 Hz), high beta (20-30 Hz), and gamma (30-45 Hz). Then, test-retest reliability was evaluated using the intraclass correlation coefficient (ICC). We also evaluated the relation between source power and the within-subject variability. In general, ICC of theta, alpha, and low beta power was fairly high (ICC > 0.6) while in delta and gamma power was lower. In source space, fronto-posterior alpha, frontal beta, and medial temporal theta showed the most reliable profiles. Signal-to-noise ratio could be partially responsible for reliability as low signal intensity resulted in high within-subject variability, but also the inherent nature of some brain rhythms in resting-state might be driving these reliability patterns. In conclusion, our results described the reliability of MEG power estimates in each frequency band, which could be considered in disease characterization or clinical trials.

Diminished testing benefits in young adults with attention-deficit hyperactivity disorder

Memory retrieval has been shown to enhance the long-term retention of tested material; however, recent research suggests that limiting attention during retrieval can decrease the benefits of testing memory. The present study examined whether testing benefits are reduced in young adults with attention-deficit hyperactivity disorder (ADHD). College students with and without ADHD read three short prose passages, each followed by a free recall test, a restudy period or a distractor task. Two days later participants recalled the passages. Although participants without ADHD did not show a significant benefit of testing over restudying, testing did produce recall benefits relative to not taking a test. These testing benefits were diminished in participants with ADHD, who did not show any advantage of testing over either restudying or no test. The absence of testing benefits in the ADHD group is likely due in part to decreased recall on the initial test. These findings have implications for improving educational practices among individuals with ADHD and also speak to the need to examine individual differences in the effectiveness of testing as a learning strategy.

Pharmaco-MEG evidence for attention related hyper-connectivity between auditory and prefrontal cortices in ADHD

The ability to attend to particular stimuli while ignoring others is crucial in goal-directed activities and has been linked with prefrontal cortical regions, including the dorsolateral prefrontal cortex (DLPFC). Both hyper- and hypo-activation in the DLPFC has been reported in patients with attention-deficit/hyperactivity disorder (ADHD) during many different cognitive tasks, but the network-level effects of such aberrant activity remain largely unknown. Using magnetoencephalography (MEG), we examined functional connectivity between regions of the DLPFC and the modality-specific auditory cortices during an auditory attention task in medicated and un-medicated adults with ADHD, and those without ADHD. Participants completed an attention task in two separate sessions (medicated/un-medicated), and each session consisted of two blocks (attend and no-attend). All MEG data were coregistered to structural MRI, corrected for head motion, and projected into source space. Subsequently, we computed the phase coherence (i.e., functional connectivity) between DLPFC regions and the auditory cortices. We found that un-medicated adults with ADHD exhibited greater phase coherence in the beta (14-30Hz) and gamma frequency (30-56Hz) range in attend and no-attend conditions compared to controls. Stimulant medication attenuated these differences, but did not fully eliminate them. These results suggest that aberrant bottom-up processing may engulf executive resources in ADHD.

Estimating the passage of minutes: deviant oscillatory frontal activity in medicated and unmedicated ADHD

OBJECTIVE

Attention-deficit/hyperactivity disorder (ADHD) is a common and extensively treated psychiatric disorder in children, which often persists into adulthood. The core diagnostic symptoms include inappropriate levels of hyperactivity, impulsivity, and/or pervasive inattention. Another crucial aspect of the disorder involves aberrations in temporal perception, which have been well documented in behavioral studies and, recently, have been the focus of neuroimaging studies. These functional magnetic resonance imaging studies have shown reduced activation in anterior cingulate and prefrontal cortices in ADHD using a time-interval discrimination task, whereby participants distinguish intervals differing by only hundreds of milliseconds.

METHOD

We used magnetoencephalography (MEG) to evaluate the cortical network serving temporal perception during a continuous, long-duration (in minutes) time estimation experiment. Briefly, medicated and unmedicated persons with ADHD, and a control group responded each time they estimated 60 s had elapsed for an undisclosed amount of time in two separate MEG sessions. All MEG data were transformed into regional source activity, and subjected to spectral analyses to derive amplitude estimates of gamma-band activity.

RESULTS

Compared to controls, unmedicated patients were less accurate time estimators and had weaker gamma activity in the anterior cingulate, supplementary motor area, and left prefrontal cortex. After medication, these patients exhibited small but significant increases in gamma across these same neural regions and significant improvements in time estimation accuracy, which correlated with the gamma activity increases.

CONCLUSION

We found deficient gamma activity in brain areas known to be crucial for timing functions, which may underlie the day-to-day abnormalities in time perception that are common in ADHD.

Electroencephalographic changes following direct current deep brain stimulation of auditory cortex: a new model for investigating neuromodulation

BACKGROUND

Although deep brain (DBS) and transcranial direct current stimulation (tDCS) are used as investigative tools and therapies for a variety of neurological and psychiatric conditions, their mechanisms of action remain poorly understood. Therefore, there is a need for new animal models of neuromodulation.

OBJECTIVE

To introduce and validate a direct current DBS (DC-DBS) model that will use the anatomic precision of intracranial electrodes, as used in DBS, to apply direct current, as used in tDCS, over primary auditory cortex (A1) and induce electroencephalographic (EEG) changes.

METHODS

Twenty-four mice were assigned to 1 of 2 stimulation groups or a sham group and were implanted with electrodes in A1. Stimulation groups underwent DC-DBS stimulation for 20 minutes at 20 μA. Auditory EEG was recorded before stimulation and at 1 hour, 1 week, and 2 weeks poststimulation. EEG was analyzed for changes in N1 (N100 in humans, N40 in mice) amplitude and latency as well as delta and theta power.

RESULTS

DC-DBS led to significant EEG changes (all P values < .05). Among the stimulated animals, there were durable reductions in delta and theta power. There were no differences within the sham group, and neither N40 latencies nor amplitudes changed across time.

CONCLUSION

Our results show DC-DBS-induced reductions in slow-wave activity consistent with recent tDCS studies. We propose that this model will provide a means to explore basic mechanisms of neuromodulation and could facilitate future application of DC-DBS in humans.

Pharmacological treatment of attention deficit hyperactivity disorder in children and adolescents: clinical strategies

Attention deficit hyperactivity disorder (ADHD) is a common neurobehavioral disorder of childhood that can result in significant functional impairment, and if not adequately treated can lead to impaired quality of life. Pharmacotherapy is considered the first-line treatment for ADHD in children and adolescents. We review both recent literature and seminal studies regarding the pharmacological treatment of ADHD in children and adolescents. There is ample evidence for the efficacy and safety of both stimulants and non-stimulants in the treatment of ADHD. We review important aspects of evaluation and assessment and discuss first-line pharmacological treatments and as well as when to consider using alternative pharmacological agents. Treatment approaches to manage frequently seen comorbid disorders with ADHD are also covered.

Gamma-frequency neuronal activity is diminished in adults with attention-deficit/hyperactivity disorder: a pharmaco-MEG study

Attention-deficit/hyperactivity disorder (ADHD) is a neurobehavioral disorder affecting approximately 4-7% of children and persisting in 2-5% of adults. The core symptoms include pervasive inattention and inappropriate levels of hyperactivity-impulsivity. High-frequency gamma activity has been implicated in the temporal binding of stimulus properties across cortical areas, and is known to be crucial for complex information processing and attentional processes in particular. Thus, we evaluated the amplitude of gamma-frequency neural responses in adults with and those without ADHD, and tested whether stimulant medications, the most common treatment for ADHD, modulate gamma activity in affected adults. Participants underwent two sessions (~75 min apart) of auditory stimulation using stimuli known to elicit 40 Hz gamma-band responses as magnetoencephalography data were acquired. Between sessions, the ADHD group (who were in maintenance therapy) were administered their daily stimulant medication and both groups were told to relax. The primary results indicated that gamma activity was weaker in the ADHD group during session one (pre-drug), but not session two (post-drug), and that gamma activity significantly increased following stimulant administration in adults with ADHD. These results suggest that ADHD is associated with reduced cortical gamma activity and that stimulants may ameliorate this abnormality.

Different neural pathways to negative affect in youth with pediatric bipolar disorder and severe mood dysregulation

Questions persist regarding the presentation of bipolar disorder (BD) in youth and the nosological significance of irritability. Of particular interest is whether severe mood dysregulation (SMD), characterized by severe non-episodic irritability, hyper-arousal, and hyper-reactivity to negative emotional stimuli, is a developmental presentation of pediatric BD and, therefore, whether the two conditions are pathophysiologically similar. We administered the affective Posner paradigm, an attentional task with a condition involving blocked goal attainment via rigged feedback. The sample included 60 youth (20 BD, 20 SMD, and 20 controls) ages 8-17. Magnetoencephalography (MEG) examined neuronal activity (4-50 Hz) following negative versus positive feedback. We also examined reaction time (RT), response accuracy, and self-reported affect. Both BD and SMD youth reported being less happy than controls during the rigged condition. Also, SMD youth reported greater arousal following negative feedback than both BD and controls, and they responded to negative feedback with significantly greater activation of the anterior cingulate cortex (ACC) and medial frontal gyrus (MFG) than controls. Compared to SMD and controls, BD youth displayed greater superior frontal gyrus (SFG) activation and decreased insula activation following negative feedback. Data suggest a greater negative affective response to blocked goal attainment in SMD versus BD and control youth. This occurs in tandem with hyperactivation of medial frontal regions in SMD youth, while BD youth show dysfunction in the SFG and insula. Data add to a growing empirical base that differentiates pediatric BD and SMD and begin to elucidate potential neural mechanisms of irritability.

The increase in theta/beta ratio on resting-state EEG in boys with attention-deficit/hyperactivity disorder is mediated by slow alpha peak frequency

Attention-deficit/hyperactivity disorder (ADHD) was found to be characterized by a deviant pattern of electrocortical activity during resting state, particularly increased theta and decreased beta activity. The first objective of the present study is to confirm whether individuals with slow alpha peak frequency contribute to the finding of increased theta activity in ADHD. The second objective is to explore the relation between resting-state brain oscillations and specific cognitive functions. From 49 boys with ADHD and 49 healthy control boys, resting-state EEG during eyes open and eyes closed was recorded, and a variety of cognitive tasks were administered. Theta and beta power and theta/beta ratio were calculated using both fixed frequency bands and individualized frequency bands. As expected, theta/beta ratio, calculated using fixed frequency bands, was significantly higher in ADHD children than control children. However, this group effect was not significant when theta/beta ratio was assessed using individualized frequency bands. No consistent relation was found between resting-state brain oscillations and cognition. The present results suggest that previous findings of increased theta/beta ratio in ADHD may reflect individuals with slow alpha peak frequencies in addition to individuals with true increased theta activity. Therefore, the often reported theta/beta ratio in ADHD can be considered a non-specific measure combining several distinct neurophysiological subgroups such as frontal theta and slowed alpha peak frequencies. Future research should elucidate the functional role of resting-state brain oscillations by investigating neurophysiological subgroups, which may have a clearer relation to cognitive functions than single frequency bands.

EEG coherence in children with attention-deficit/hyperactivity disorder: differences between good and poor responders to methylphenidate

This retrospective study investigated differences in regional derivations of EEG coherence between good and poor responders to methylphenidate (MPH) in children (aged 8-12 years) with the combined type of attention-deficit/hyperactivity disorder (AD/HD). Participants included groups of good and poor male MPH responders and an aged-matched group of male controls. An eyes-closed, resting electroencephalogram (EEG) was recorded from 21 electrode sites. Coherence was calculated from eight intrahemispheric and eight interhemispheric electrode pairs, for the delta, theta, alpha and beta frequency bands. Compared with controls, the AD/HD participants had enhanced laterality over short-medium inter-electrode distances, and elevated frontal interhemispheric coherences, in the theta band. Good MPH responders had higher intrahemispheric coherences than poor MPH responders over short-medium and long inter-electrode distances in the beta band. Enhanced laterality at short-medium inter-electrode distances suggests that the AD/HD children may have a developmental lag in short-axonal connections in the left hemisphere. Elevated frontal interhemispheric theta coherence consistently indicates some frontal dysfunction in AD/HD. The beta coherence differences found between good and poor MPH responders could indicate that good MPH responders have some type of structural dysfunction associated with cortical connections involved in attention/arousal.

Complexity analysis of spontaneous brain activity in attention-deficit/hyperactivity disorder: diagnostic implications

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) is defined as the most common neurobehavioral disorder of childhood, but an objective diagnostic test is not available yet to date. Neurophychological, neuroimaging, and neurophysiological research offer ample evidence of brain and behavioral dysfunctions in ADHD, but these findings have not been useful as a diagnostic test.

METHODS

Whole-head magnetoencephalographic recordings were obtained from 14 diagnosed ADHD patients and 14 healthy children during resting conditions. Lempel-Ziv complexity (LZC) values were obtained for each channel and child and averaged in five sensor groups: anterior, central, left lateral, right lateral, and posterior.

RESULTS

Lempel-Ziv complexity scores were significantly higher in control subjects, with the maximum value in anterior region. Combining age and anterior complexity values allowed the correct classification of ADHD patients and control subjects with a 93% sensitivity and 79% specificity. Control subjects showed an age-related monotonic increase of LZC scores in all sensor groups, while children with ADHD exhibited a nonsignificant tendency toward decreased LZC scores. The age-related divergence resulted in a 100% specificity in children older than 9 years.

CONCLUSIONS

Results support the role of a frontal hypoactivity in the diagnosis of ADHD. Moreover, the age-related divergence of complexity scores between ADHD patients and control subjects might reflect distinctive developmental trajectories. This interpretation of our results is in agreement with recent investigations reporting a delay of cortical maturation in the prefrontal cortex.

Development of Inattention, Impulsivity, and Processing Speed as Measured by the d2 Test: Results of a Large Cross-sectional Study in Children Aged 7–13

The development of three aspects of selective attention was studied in 451 Dutch schoolchildren attending second to sixth grade. Selective attention was measured with the d2 Test of attention. The largest age differences were found for processing speed that continued to improve until the sixth grade. Impulsivity, as measured by the percentage of errors of commission, decreased until the fourth grade. Inattention, measured by the percentage of errors of omission, was stable in all grades. Processing speed and impulsivity were correlated with the score on the Attention Problems subscale of the Child Behavior Checklist. These results imply that selective attention continues to develop, at least, until the end of elementary school. The findings are support for a step-wise model of cognitive development (P. Anderson, 2002).