Stefan Katja, Wycislo Matthias, Classen Joseph
Human Cortical Physiology and Motor Control Laboratory, Department of Neurology, University of Würzburg, Germany.
J Neurophysiol. 2004 Jul;92(1):66-72. doi: 10.1152/jn.00383.2003. Epub 2004 Jan 14.
The role of attention in generating motor memories remains controversial principally because it is difficult to separate the effects of attention from changes in kinematics of motor performance. We attempted to disentangle attention from performance effects by varying attention while plasticity was induced in human primary motor cortex by external stimulation in the absence of voluntary movement. A paired associative stimulation (PAS) protocol was employed consisting of repetitive application of single afferent electric stimuli, delivered to the right median nerve, paired with single-pulse transcranial magnetic stimulation (TMS) over the optimal site for activation of the right abductor pollicis brevis muscle (APB) to generate near-synchronous events in the left primary motor cortex. In experiment 1, the spatial location of attention was varied. PAS failed to induce plasticity when the subject's attention was directed to their left hand, away from the right target hand the cortical representation of which was being stimulated by PAS. In experiment 2, the grade of attention to the target hand was manipulated. PAS-induced plasticity was maximal when the subject viewed their target hand, and its magnitude was slightly reduced when the subject could only feel their hand. Conversely, plasticity was completely blocked when the subject's attention was diverted from the target hand by a competing cognitive task. A similar modulation by attention was observed for PAS-induced changes in the duration of the silent period evoked by TMS in voluntarily contracted muscle. Associative plasticity in the human motor cortex depends decisively on attention.
注意力在产生运动记忆中的作用仍存在争议，主要原因是难以将注意力的影响与运动表现的运动学变化区分开来。我们试图通过在无自主运动的情况下，利用外部刺激在人类初级运动皮层诱导可塑性时改变注意力，来区分注意力与表现效应。采用了一种配对联想刺激（PAS）方案，包括重复施加单个传入电刺激，刺激右侧正中神经，并在激活右侧拇短展肌（APB）的最佳部位进行单脉冲经颅磁刺激（TMS），以在左侧初级运动皮层产生近同步事件。在实验1中，注意力的空间位置发生了变化。当受试者将注意力指向其左手（远离PAS正在刺激其皮层表征的右侧目标手）时，PAS未能诱导可塑性。在实验2中，对目标手的注意力程度得到了控制。当受试者观看其目标手时，PAS诱导的可塑性最大，而当受试者只能感觉到其手时，可塑性的幅度略有降低。相反地，当受试者的注意力被一项竞争性认知任务从目标手上转移时，可塑性完全被阻断。对于PAS诱导的在自愿收缩肌肉中TMS诱发的静息期持续时间的变化，也观察到了类似的注意力调节作用。人类运动皮层中的联合可塑性决定性地依赖于注意力。
