Dissociable contribution of the parietal and frontal cortex to coding movement direction and amplitude.
Dissociable contribution of the parietal and frontal cortex to coding movement direction and amplitude.
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DOI：
10.3389/fnhum.2015.00241
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发表时间：
2015
影响因子：
2.9
通讯作者：
Olivier E
中科院分区：
文献类型：
--
作者：
Davare M;Zénon A;Desmurget M;Olivier E
为了够到一个物体，我们必须将它的空间位置转换成适当的运动指令，合并运动方向和幅度。在人类中，有人认为这种视觉运动转变发生在背内侧顶额通路中，尽管构成“到达回路”的区域的因果贡献仍然未知。在这里，我们在健康志愿者中使用经颅磁刺激（TMS）来破坏每个半球的内侧顶内区（mIPS）或背侧运动前皮质（PMd）的功能。该任务包括用右手腕朝向位于不同方向和偏心度的目标进行步进跟踪运动;目标在整个试验中可见（目标开启）或闪烁200 ms（目标关闭）。左侧和右侧mIPS中断导致朝向对侧目标进行的运动的初始方向错误。这些错误在目标开启条件下在线纠正，但当目标闪烁200 ms时，mIPS TMS表现为更大的端点扩展。相比之下，左PMd虚拟病变导致更高的加速度和速度峰值-两个参数通常用于探测计划的运动幅度-不考虑目标位置，半野和演示条件;在目标关闭条件下，左PMd TMS诱导过冲，并增加了沿沿着目标方向的轴的终点分散。这些结果表明，左PMd干预运动准备过程中的编码幅度。导致方向和幅度误差的临界TMS时间是不同的，即mIPS运动开始前160-100 ms和左PMd运动开始前100-40 ms。TMS应用于右PMD没有显著影响。这些结果表明，在运动准备过程中，目标导向运动的方向和幅度由不同的皮层区域，在不同的时间，并根据特定的半球组织处理。
To reach for an object, we must convert its spatial location into an appropriate motor command, merging movement direction and amplitude. In humans, it has been suggested that this visuo-motor transformation occurs in a dorsomedial parieto-frontal pathway, although the causal contribution of the areas constituting the “reaching circuit” remains unknown. Here we used transcranial magnetic stimulation (TMS) in healthy volunteers to disrupt the function of either the medial intraparietal area (mIPS) or dorsal premotor cortex (PMd), in each hemisphere. The task consisted in performing step-tracking movements with the right wrist towards targets located in different directions and eccentricities; targets were either visible for the whole trial (Target-ON) or flashed for 200 ms (Target-OFF). Left and right mIPS disruption led to errors in the initial direction of movements performed towards contralateral targets. These errors were corrected online in the Target-ON condition but when the target was flashed for 200 ms, mIPS TMS manifested as a larger endpoint spreading. In contrast, left PMd virtual lesions led to higher acceleration and velocity peaks—two parameters typically used to probe the planned movement amplitude—irrespective of the target position, hemifield and presentation condition; in the Target-OFF condition, left PMd TMS induced overshooting and increased the endpoint dispersion along the axis of the target direction. These results indicate that left PMd intervenes in coding amplitude during movement preparation. The critical TMS timings leading to errors in direction and amplitude were different, namely 160–100 ms before movement onset for mIPS and 100–40 ms for left PMd. TMS applied over right PMd had no significant effect. These results demonstrate that, during motor preparation, direction and amplitude of goal-directed movements are processed by different cortical areas, at distinct timings, and according to a specific hemispheric organization.
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