The interplay between attention, alertness, and motor planning is crucial for our manual interactions. To investigate the neural bases of this interaction and challenge the views that attention cannot be disentangled from motor planning, we instructed human volunteers of both sexes to plan and execute reaching movements while attending to the target, while attending elsewhere, or without constraining attention. We recorded reaction times to reach initiation and pupil diameter and interfered with the functions of the medial posterior parietal cortex (mPPC) with online repetitive transcranial magnetic stimulation to test the causal role of this cortical region in the interplay between spatial attention and reaching. We found that mPPC plays a key role in the spatial association of reach planning and covert attention. Moreover, we have found that alertness, measured by pupil size, is a good predictor of the promptness of reach initiation only if we plan a reach to attended targets, and mPPC is causally involved in this coupling. Different from previous understanding, we suggest that mPPC is neither involved in reach planning per se, nor in sustained covert attention in the absence of a reach plan, but it is specifically involved in attention functional to reaching.

注意力、警觉性和运动规划之间的相互作用对于我们的手动交互至关重要。为了研究这种互动的神经基础并挑战注意力无法与运动规划分开的观点，我们指导男女人类志愿者在关注目标的同时，在其他地方参加或不限制注意力的情况下计划和执行到达动作。我们记录了达到起始和瞳孔直径的反应时间，并通过在线重复经颅磁刺激干扰内侧后顶叶皮层 （mPPC） 的功能，以测试该皮质区域在空间注意力和到达之间相互作用中的因果作用。我们发现 mPPC 在覆盖率规划和隐蔽注意力的空间关联中起关键作用。此外，我们发现，只有当我们计划到达有人值守的目标时，以瞳孔大小衡量的警觉性才能很好地预测到达开始的迅速性，而 mPPC 与这种耦合有因果关系。与以前的理解不同，我们认为 mPPC 本身既不参与覆盖率规划本身，也不涉及在没有覆盖率计划的情况下持续的隐蔽关注，但它专门涉及覆盖率的注意力功能。