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The neuronal processes underlying response inhibition are often studied using either event-related potentials (ERPs) or by applying transcranial magnetic stimulation (TMS) to investigate excitatory and inhibitory processes in the motor system. We performed a more refined analysis of response inhibition by combining both approaches with the aim of identifying an interplay between ERPs and TMS parameters. During a go/nogo task, motor system excitability was measured using TMS single and double pulses and brain electrical activity was recorded in healthy adults (n=14). Each participant completed two testing sessions, once on placebo and once on methylphenidate (double-blind, crossover design). Studying the effects of methylphenidate served as an example application for this combined approach. Developing regression models, inhibition-related TMS measures (e.g., short intracortical inhibition) and the contingent negative variation explained about 85% of the variance of the nogo-P3 under both MPH and placebo medication. The smaller the inhibitory effect in the motor system, the more terminal response control was required and the more resources were allocated for the evaluation of the inhibitory process, respectively, as indicated by a larger P3. Thus, an interplay between processes in the motor system (cortex) and control processes with sources in the prefrontal cortex and the anterior cingulate cortex (ACC) may take place, acting complementarily to facilitate a correct nogo-response. While ERPs rather represent initiation and monitoring of inhibitory processes and response control, motor inhibition may be best analyzed using TMS. A combined ERP/TMS analysis may allow for the development of distinct models concerning the interplay of processes involved in response inhibition.

A variety of event-related potential (ERP) based studies have shown differences in neuronal processes underlying attention, inhibition and error processing in children with attention-deficit/hyperactivity disorder (ADHD) compared to controls. However, so far there are no studies that have compared children with ADHD and typically developing (TD) children regarding effects in ERP components associated with the attention network test (ANT). The ANT allows to differentiate between three particular aspects of attention: alerting, orienting, conflict. Twenty-five children with ADHD and 19 TD children (comparable with respect to age, sex, and IQ) performed the ANT while ERPs were recorded. Based on DSM-IV, the group of children with ADHD was divided in an inattentive (ADHDin, n=10) and a combined (ADHDcom, n=15) subgroup. On the performance level, the ADHD group showed a significantly higher variability of reaction times. Concerning ERP measures, smaller cue-P3 amplitudes were found in the ADHD group indicating that children with ADHD allocate less attentional resources for cue processing. In addition, the target-P3 in ADHD showed smaller amplitudes. Subgroup analysis revealed reduced cue-P3 amplitudes in both subgroups and reduced target-P3 amplitudes in ADHDin compared to TD children. Except for a higher alerting score in ADHD after correction for cue-P3 group differences, performance data revealed no group differences specific for the three attention networks. No group differences related to the attention networks were observed at the ERP level. Our results suggest that deviant attentional processing in children with ADHD is only partly related to ANT-specific effects. Findings are compatible with the model of a suboptimal energetic state regulation in ADHD. Furthermore, our results suggest that deviant cue processing in ADHD and related differences in task modulations should be accounted for in data analysis.

In a randomized controlled trial, neurofeedback (NF) training was found to be superior to a computerised attention skills training concerning the reduction of ADHD symptomatology (Gevensleben et al., 2009). The aims of this investigation were to assess the impact of different NF protocols (theta/beta training and training of slow cortical potentials, SCPs) on the resting EEG and the association between distinct EEG measures and behavioral improvements. In 72 (of initially 102) children with ADHD, aged 8-12, EEG changes after either a NF training (n=46) or the control training (n=26) could be studied. The combined NF training consisted of one block of theta/beta training and one block of SCP training, each block comprising 18 units of 50 minutes (balanced order). Spontaneous EEG was recorded in a two-minute resting condition before the start of the training, between the two training blocks and after the end of the training. Activity in the different EEG frequency bands was analyzed. In contrast to the control condition, the combined NF training was accompanied by a reduction of theta activity. Protocol-specific EEG changes (theta/beta training: decrease of posterior-midline theta activity; SCP training: increase of central-midline alpha activity) were associated with improvements in the German ADHD rating scale. Related EEG-based predictors were obtained. Thus, differential EEG patterns for theta/beta and SCP training provide further evidence that distinct neuronal mechanisms may contribute to similar behavioral improvements in children with ADHD.