Department for Child and Adolescent Psychiatry, Centre for Psychosocial Medicine, University of Heidelberg, Blumenstr. 8, 69115 Heidelberg, Germany.
Brain. 2012 Jul;135(Pt 7):2215-30. doi: 10.1093/brain/aws071. Epub 2012 Apr 3.
Attention deficit hyperactivity disorder is one of the most frequent neuropsychiatric disorders in childhood. Transcranial magnetic stimulation studies based on muscle responses (motor-evoked potentials) suggested that reduced motor inhibition contributes to hyperactivity, a core symptom of the disease. Here we employed the N100 component of the electroencephalographic response to transcranial magnetic stimulation as a novel marker for a direct assessment of cortical inhibitory processes, which has not been examined in attention deficit hyperactivity disorder so far. We further investigated to what extent affected children were able to regulate motor cortical inhibition, and whether effects of age on the electroencephalographic response to transcranial magnetic stimulation were compatible with either a delay in brain maturation or a qualitatively different development. N100 amplitude evoked by transcranial magnetic stimulation and its age-dependent development were assessed in 20 children with attention deficit hyperactivity disorder and 19 healthy control children (8-14 years) by 64-channel electroencephalography. Amplitude and latency of the N100 component were compared at rest, during response preparation in a forewarned motor reaction time task and during movement execution. The amplitude of the N100 component at rest was significantly lower and its latency tended to be shorter in children with attention deficit hyperactivity disorder. Only in controls, N100 amplitude to transcranial magnetic stimulation was reduced by response preparation. During movement execution, N100 amplitude decreased while motor evoked potential amplitudes showed facilitation, indicating that the electroencephalographic response to transcranial magnetic stimulation provides further information on cortical excitability independent of motor evoked potential amplitudes and spinal influences. Children with attention deficit hyperactivity disorder showed a smaller N100 amplitude reduction during movement execution compared with control children. The N100 amplitude evoked by transcranial magnetic stimulation decreased with increasing age in both groups. The N100 reduction in children with attention deficit hyperactivity disorder at all ages suggests a qualitative difference rather than delayed development of cortical inhibition in this disease. Findings further suggest that top-down control of motor cortical inhibition is reduced in children with attention deficit hyperactivity disorder. We conclude that evoked potentials in response to transcranial magnetic stimulation are a promising new marker of cortical inhibition in attention deficit hyperactivity disorder during childhood.
注意缺陷多动障碍是儿童期最常见的神经精神疾病之一。基于肌肉反应（运动诱发电位）的经颅磁刺激研究表明，运动抑制减少导致多动，这是该疾病的核心症状。在这里，我们采用经颅磁刺激的脑电图反应中的 N100 成分作为皮质抑制过程直接评估的新标记物，迄今为止尚未在注意缺陷多动障碍中进行过检查。我们进一步研究了受影响的儿童在多大程度上能够调节运动皮质抑制，以及年龄对经颅磁刺激的脑电图反应的影响是否与大脑成熟的延迟或质的不同发展相兼容。通过 64 通道脑电图评估了 20 名注意缺陷多动障碍儿童和 19 名健康对照儿童（8-14 岁）的经颅磁刺激诱发的 N100 幅度及其年龄依赖性发育。在静息状态、预警运动反应时间任务的反应准备期间以及运动执行期间比较 N100 成分的幅度和潜伏期。静息时 N100 成分的幅度在注意缺陷多动障碍儿童中明显较低，其潜伏期趋于较短。仅在对照组中，经颅磁刺激的 N100 幅度通过反应准备而降低。在运动执行期间，N100 幅度降低，而运动诱发电位幅度增加，这表明经颅磁刺激的脑电图反应提供了关于皮质兴奋性的进一步信息，与运动诱发电位幅度和脊髓影响无关。与对照儿童相比，注意缺陷多动障碍儿童在运动执行期间的 N100 幅度减少较小。两组的 N100 幅度均随年龄的增加而降低。注意缺陷多动障碍儿童在所有年龄段的 N100 减少表明皮质抑制的质的差异而不是该疾病的发育延迟。研究结果进一步表明，注意缺陷多动障碍儿童的运动皮质抑制的自上而下控制减少。我们得出结论，经颅磁刺激反应中的诱发电位是儿童期注意缺陷多动障碍皮质抑制的一种很有前途的新标记物。
