Motor cortical inhibition in ADHD: modulation of the transcranial magnetic stimulation-evoked N100 in a response control task

Abstract

The N100 component, evoked by transcranial magnetic stimulation (TMS) and electroencephalography is associated with the activation of inhibitory cortical circuits and has recently been suggested as a potential marker of inhibition in attention-deficit/hyperactivity disorder (ADHD). The aim of the present ADHD study was to investigate the modulation of the TMS-N100 in go and nogo trials of a response control task considering stages of response preparation, activation, execution and inhibition. Eighteen children with ADHD and 19 typically developing children, aged 10-14 years, were assessed. TMS was delivered over the left motor cortex, the TMS-N100 was measured at electrode P3. The TMS-N100 was determined at rest and at different time points (50 ms before S2; 150, 300 and 500 ms after S2) in a cued go/nogo task (S1-S2 paradigm). Correlations between the TMS-N100 measures, MEP-related TMS measures (e.g., short-interval intracortical inhibition) and performance measures were calculated. At rest, the amplitude of TMS-N100 was not found to be significantly reduced in the ADHD group. During the go/nogo task, children with ADHD showed a smaller increase of TMS-N100 amplitude in go trials and a smaller decrease after inhibiting a response. In go trials, a lower TMS-N100 was associated with a smaller variability of reaction times. A smaller TMS-N100 modulation extends the picture of cortical inhibition deficits in ADHD. Findings suggest a functional involvement of the mechanisms underlying the TMS-N100 at the motor output stage.

Development of cortical motor circuits between childhood and adulthood: A navigated TMS‐HdEEG study

“…Previous developmental TMS-EEG studies have focused on TEP in the N100 latency range and shown that N100 is increased in children compared with adults [Bender et al, 2005;D'Agati et al, 2014;Helfrich et al, 2012]. When using a suprathreshold stimulus intensity, TMS elicited a notably enhanced GMFP response in children compared with adults, with the adolescents' responses lying between those of children and adults.…”

“…Studies on TEPs in children are scarce and have solely focused on the N100 component [Bender et al, 2005;D'Agati et al, 2014;Helfrich et al, 2012;Jarczok et al, 2016]. In their pioneering article, Bender et al [2005] showed that TMS-evoked N100 undergoes maturational decline and could serve as a test of cortical integrity and inhibitory function in children.…”

Noninvasive Brain Stimulation in Pediatric Attention-Deficit Hyperactivity Disorder (ADHD)

“…The negative deflection of EEG at 100 milliseconds after a TMS pulse, termed the N100, is a proxy of cortical inhibitory processes 76-80 . Recent studies have shown N100 abnormalities in association with ADHD 808182 .…”

Maturation changes the excitability and effective connectivity of the frontal lobe: A developmental TMS–EEG study

“…There have been few TMS–EEG studies in children, and they have all described TEPs to motor cortex stimulation (Bender et al, ; D'Agati et al, ; Helfrich et al, ; Jarczok et al, ; Määttä et al, ). The results from these studies indicate that the TMS‐evoked N100 component, the most prominent TEP after motor cortex stimulation, declines with maturation and could serve as a test of cortical inhibitory function in children (Bender et al, ; D'Agati et al, ; Helfrich et al, ). Moreover, these results demonstrate that interhemispheric signal propagation between motor cortices increases as a function of age (Jarczok et al, ; Määttä et al, ) and that the complexity of TEP morphology increases and signal spreading facilitates within ipsilateral and contralateral cortices, reflecting developmental changes in motor cortex functional connectivity (Määttä et al, ).…”