Influence of Stimulant Medication and Response Speed on Lateralization of Movement-Related Potentials in Attention-Deficit/Hyperactivity Disorder

BackgroundHyperactivity is one of the core symptoms in attention deficit hyperactivity disorder (ADHD). However, it remains unclear in which way the motor system itself and its development are affected by the disorder. Movement-related potentials (MRP) can separate different stages of movement execution, from the programming of a movement to motor post-processing and memory traces. Pre-movement MRP are absent or positive during early childhood and display a developmental increase of negativity. MethodsWe examined the influences of response-speed, an indicator of the level of attention, and stimulant medication on lateralized MRP in 16 children with combined type ADHD compared to 20 matched healthy controls. ResultsWe detected a significantly diminished lateralisation of MRP over the pre-motor and primary motor cortex during movement execution (initial motor potential peak, iMP) in patients with ADHD. Fast reactions (indicating increased visuo-motor attention) led to increased lateralized negativity during movement execution only in healthy controls, while in children with ADHD faster reaction times were associated with more positive amplitudes. Even though stimulant medication had some effect on attenuating group differences in lateralized MRP, this effect was insufficient to normalize lateralized iMP amplitudes. ConclusionsA reduced focal (lateralized) motor cortex activation during the command to muscle contraction points towards an immature motor system and a maturation delay of the (pre-) motor cortex in children with ADHD. A delayed maturation of the neuronal circuitry, which involves primary motor cortex, may contribute to ADHD pathophysiology.背景 多动是注意缺陷多动障碍（ADHD）的核心症状之一。然而目前仍不明确该病症会以何种方式影响运动系统本身及其发育进程。运动相关电位（MRP）可区分运动执行的全流程阶段，涵盖运动规划、运动后处理与记忆痕迹形成。儿童早期的运动前MRP呈缺失或正向电位状态，并随发育进程逐渐出现负向电位增强。 方法 本研究纳入16名混合型注意缺陷多动障碍患儿与20名人口学特征匹配的健康对照儿童，考察了反应速度（注意力水平的一项指标）与中枢兴奋药物对偏侧化MRP的影响。 结果 研究发现，注意缺陷多动障碍患儿在运动执行阶段（初始运动电位峰，iMP），其运动前皮层与初级运动皮层上的MRP偏侧化程度显著降低。仅在健康对照儿童中，快速反应（提示视运动注意力提升）会在运动执行阶段带来更强的偏侧化负向电位；而在注意缺陷多动障碍患儿中，更快的反应时则对应更为正向的电位幅值。尽管中枢兴奋药物可在一定程度上缩小两组间偏侧化MRP的差异，但该效果不足以使偏侧化iMP幅值恢复至正常水平。 结论 在下达肌肉收缩指令时，注意缺陷多动障碍患儿出现了局灶性（偏侧化）运动皮层激活减弱的现象，提示其运动系统发育未成熟，且（运动前）初级运动皮层存在成熟延迟。涉及初级运动皮层的神经环路成熟延迟，可能参与了注意缺陷多动障碍的病理生理过程。