Motor hyperactivity is one of the most outstanding symptoms of attention deficit hyperactivity disorder (ADHD) which might be caused by a disturbed inhibitory motor control. Using focal transcranial magnetic stimulation (TMS) we tested the cortico-callosal inhibition (duration and latency of the ipsilateral Silent Period, iSP) in 23 children with ADHD (mean age 11+/-2.6 years) before and on treatment with methylphenidate (MPH). iSP latency was age correlated, whereas iSP duration as well as Conners scores were age independent. Analyses of mean differences revealed a significant prolongation of iSP duration (p=0.001), shortening of iSP latency (p=0.027) and reduction of Conners score (p=0.001) under medication. Increase of iSP duration and reduction of Conners score under medication were significantly correlated (t=-9.87, p=0.016). Reduced iSP duration and prolonged iSP latency in ADHD children could be the result of a disturbed transcallosally mediated inhibition, most probable due to a combination of maturation deficits of callosal fiber tracts as well as neuronal synaptical transmission within the neuronal network between ipsilaterally stimulated cortex layer III--the origin of transcallosal motor-cortical fibers--and contralateral layer V, the origin of the pyramidal tract. MPH may indirectly improve the dysbalance between excitatory and inhibitory interneuronal activities of this neuronal network via dopaminergic modulatory effects of the striato-thalamo-cortical loop.

译文

运动多动是注意力缺陷多动障碍 (ADHD) 最突出的症状之一,可能是由抑制性运动控制障碍引起的。使用局灶性经颅磁刺激 (TMS),我们在接受哌醋甲酯 (MPH) 治疗之前和治疗时测试了23名ADHD儿童 (平均年龄11/-2.6岁) 的皮质-call抑制作用 (同侧静默期的持续时间和潜伏期,iSP)。iSP延迟与年龄相关,而iSP持续时间和Conners评分与年龄无关。平均差异分析显示,在药物治疗下,iSP持续时间显着延长 (p = 0.001),iSP潜伏期缩短 (p = 0.027) 和Conners评分降低 (p = 0.001)。iSP持续时间的增加与药物治疗下Conners评分的降低显著相关 (t =-9.87,p = 0.016)。ADHD儿童的iSP持续时间减少和iSP潜伏期延长可能是跨call介导的抑制干扰的结果,最有可能的原因是,在同侧刺激的皮层III层 (经胼胝体运动皮质纤维的起源) 和对侧V层 (锥体束的起源) 之间的神经元网络内,胼胝体纤维束的成熟缺陷以及神经元突触传递的组合。MPH可能通过纹状体-丘脑-皮质环的多巴胺能调节作用间接改善该神经元网络的兴奋性和抑制性神经元活动之间的失衡。

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