Katleen Geladé

Alterations in the ventral attention network during the stop-signal task in children with ADHD: an event-related potential source imaging study

Objective: Deficits in response inhibition figure prominently in models of ADHD; however, attentional deficiencies may better explain previous findings of impaired response inhibition in ADHD. We tested this hypothesis at the neurophysiological level. Method: Dense array ERPs (event-related potentials) were obtained for 46 children with ADHD and 51 controls using the stop-signal task (SST). Early and late components were compared between groups. N2 and P3 components were localized with LAURA distributed linear inverse solution. Results: A success-related N1 modulation was only apparent in the ADHD group. N2 and P3 amplitudes were reduced in ADHD. During the successful inhibition N2, the ADHD group showed reduced activation in right inferior frontal gyrus (rIFG), supplementary motor area (SMA), and right temporoparietal junction (rTPJ), and during failed inhibition in the rIFG. During the successful inhibition P3, reduced activation was found in anterior cingulate cortex (ACC) and SMA. Conclusion: Impairments in the ventral attention network contribute to the psychopathology of ADHD and challenge the dominant view that ADHD is underpinned by impaired inhibitory control.

Behavioral Effects of Neurofeedback Compared to Stimulants and Physical Activity in Attention-Deficit/Hyperactivity Disorder: A Randomized Controlled Trial

OBJECTIVE The efficacy of neurofeedback as a treatment for attention-deficit/hyperactivity disorder (ADHD), and whether neurofeedback is a viable alternative for stimulant medication, is still an intensely debated subject. The current randomized controlled trial compared neurofeedback to (1) optimally titrated methylphenidate and (2) a semi-active control intervention, physical activity, to account for nonspecific effects. METHODS A multicenter 3-way parallel-group study with balanced randomization was conducted. Children with a DSM-IV-TR diagnosis of ADHD, aged 7-13 years, were randomly allocated to receive neurofeedback (n = 39), methylphenidate (n = 36), or physical activity (n = 37) over a period of 10-12 weeks. Neurofeedback comprised theta/beta training on the vertex (Cz). Physical activity consisted of moderate to vigorous intensity exercises. Neurofeedback and physical activity were balanced in terms of number (~30) and duration of sessions. A double-blind pseudorandomized placebo-controlled crossover titration procedure was used to determine an optimal dose in the methylphenidate intervention. Parent and teacher ratings on the Strengths and Difficulties Questionnaire (SDQ) and Strengths and Weaknesses of ADHD Symptoms and Normal Behavior (SWAN) were used to assess intervention outcomes. Data collection took place between September 2010 and March 2014. RESULTS Intention-to-treat analyses revealed an improvement in parent-reported behavior on the SDQ and the SWAN Hyperactivity/Impulsivity scale, irrespective of received intervention (ηp² = 0.21-0.22, P ≤ .001), whereas the SWAN Inattention scale revealed more improvement in children who received methylphenidate than neurofeedback and physical activity (ηp² = 0.13, P ≤ .001). Teachers reported a decrease of ADHD symptoms on all measures for methylphenidate, but not for neurofeedback or physical activity (range of ηp² = 0.14-0.29, P < .001). CONCLUSIONS The current study found that optimally titrated methylphenidate is superior to neurofeedback and physical activity in decreasing ADHD symptoms in children with ADHD. TRIAL REGISTRATION ClinicalTrials.gov identifier: NCT01363544.

An ERP source imaging study of the oddball task in children with Attention Deficit/Hyperactivity Disorder

OBJECTIVE Children with ADHD have difficulties attending to task-relevant events, which has been consistently associated with reductions in the amplitude of the P3b event-related potential (ERP) component. However, the underlying neural networks involved in this P3b reduction remain elusive. Therefore, this study explored source localization of P3b alterations in children with ADHD, aiming at a more detailed account of attentional difficulties. METHODS Dense array ERPs were obtained for 36 children with ADHD and 49 typically developing children (TD) using an auditory oddball task. The P3b component (310-410 ms) was individually localized with the LAURA distributed linear inverse solution method and compared between groups. RESULTS The ADHD group showed reduced P3b amplitudes in response to targets compared to the TD group. Differences were located primarily in frontopolar (cinguloopercular network, BA10) and temporoparietal regions (ventral attention network, BA39 and 19) in the left hemisphere. Reductions in P3b amplitudes were related to more inattention and hyperactivity/impulsivity problems in the ADHD group. CONCLUSIONS The results show alterations in both top-down and bottom-up attention-related brain areas, which may underlie P3b amplitude reductions in children with ADHD. SIGNIFICANCE This study provides novel data on both temporal and spatial aspects of dysfunctional attention processes in ADHD.

Neural network topology in ADHD; evidence for maturational delay and default-mode network alterations

OBJECTIVE Attention-deficit/hyperactivity disorder (ADHD) has been associated with widespread brain abnormalities in white and grey matter, affecting not only local, but global functional networks as well. In this study, we explored these functional networks using source-reconstructed electroencephalography in ADHD and typically developing (TD) children. We expected evidence for maturational delay, with underlying abnormalities in the default mode network. METHODS Electroencephalograms were recorded in ADHD (n=42) and TD (n=43) during rest, and functional connectivity (phase lag index) and graph (minimum spanning tree) parameters were derived. Dependent variables were global and local network metrics in theta, alpha and beta bands. RESULTS We found evidence for a more centralized functional network in ADHD compared to TD children, with decreased diameter in the alpha band (ηp2=0.06) and increased leaf fraction (ηp2=0.11 and 0.08) in the alpha and beta bands, with underlying abnormalities in hub regions of the brain, including default mode network. CONCLUSIONS The finding of a more centralized network is in line with maturational delay models of ADHD and should be replicated in longitudinal designs. SIGNIFICANCE This study contributes to the literature by combining high temporal and spatial resolution to construct EEG network topology, and associates maturational-delay and default-mode interference hypotheses of ADHD.