Hyperactivity in motor response inhibition networks in unmedicated children with attention deficit-hyperactivity disorder

<b>Objectives:</b> Hypo/reduced activity in motor response inhibition (RI) cerebral networks was recently proposed as a promising specific neurobiological marker of attention deficit-hyperactivity disorder (ADHD). Before adopting such a pattern as a key diagnosis tool, we aim to replicate in an independent study the mechanisms underlying reduced RI-related activity in ADHD, after controlling for potentially confounding effects. <b>Methods:</b> In this fMRI study, we investigated the neural networks mediating successful and failed motor RI in children with ADHD and typically developing children (TDC) using the stop-signal task (SST) paradigm. <b>Results:</b> In contrast to hypofrontality predictions, children with ADHD exhibit increased neural activity during successful response inhibition in an RI-related brain network encompassing the indirect and/or hyperdirect pathways between the basal ganglia and cortex. Voxel-based morphometry analyses have further evidenced reduced grey matter volume in the left caudate in children with ADHD, which paralleled higher functional responses. Finally, connectivity analyses disclosed tighter coupling between a set of cortical regions and the right caudate as well as the right IFG, networks involved in successful RI. <b>Conclusions:</b> Hypo/reduced activity in RI cerebral networks in children with ADHD cannot at this time be considered as a systematic biomarker for ADHD.

<b>研究目标：</b> 近期有研究提出，运动反应抑制（motor response inhibition, RI）脑网络的活动低下或减弱，可作为注意缺陷多动障碍（attention deficit-hyperactivity disorder, ADHD）极具潜力的特异性神经生物学标志物。在将该模式作为核心诊断工具之前，我们旨在通过一项独立研究，在控制潜在混杂效应的前提下，复现ADHD患儿中运动反应抑制相关活动减弱的潜在机制。
<b>研究方法：</b> 本项功能磁共振成像（fMRI）研究采用停止信号任务（stop-signal task, SST）范式，探究了ADHD患儿与典型发育儿童（typically developing children, TDC）体内介导成功与失败运动反应抑制的神经网络。
<b>研究结果：</b> 与前额叶活动低下的预测相悖，ADHD患儿在涵盖基底神经节与皮层间间接通路和/或超直接通路的运动反应抑制相关脑网络中，完成成功反应抑制时表现出增强的神经活动。基于体素的形态测量学分析进一步证实，ADHD患儿左侧尾状核的灰质体积有所降低，这与其更高的功能响应水平相平行。最后，连通性分析显示，一组皮层区域与右侧尾状核及右侧额下回（inferior frontal gyrus, IFG）之间的耦合更为紧密，而这些网络正是参与成功运动反应抑制的关键通路。
<b>研究结论：</b> 目前尚不能将ADHD患儿运动反应抑制脑网络活动低下或减弱的现象，视为注意缺陷多动障碍的系统性生物标志物。