When performing movements in rapid succession, the brain needs to coordinate ongoing execution with the preparation of an upcoming action. Here we identify the processes and brain areas involved in this ability of online preparation. Human participants (both male and female) performed pairs of single-finger presses or three-finger chords in rapid succession, while 7T fMRI was recorded. In the overlap condition, they could prepare the second movement during the first response and in the nonoverlap condition only after the first response was completed. Despite matched perceptual and movement requirements, fMRI revealed increased brain activity in the overlap condition in regions along the intraparietal sulcus and ventral visual stream. Multivariate analyses suggested that these areas are involved in stimulus identification and action selection. In contrast, the dorsal premotor cortex, known to be involved in planning upcoming movements, showed no discernible signs of heightened activity. This observation suggests that the bottleneck during simultaneous action execution and preparation arises at the level of stimulus identification and action selection, whereas movement planning in the premotor cortex can unfold concurrently with the execution of a current action without requiring additional neural activity.

当快速连续执行动作时，大脑需要协调正在进行的执行与即将到来的动作的准备。在这里，我们确定了这种在线准备能力所涉及的过程和大脑区域。人类参与者（男性和女性）快速连续进行双指按压或三指和弦，同时记录 7T fMRI。在重叠条件下，他们可以在第一次响应期间准备第二个动作，而在非重叠条件下，他们只能在第一次响应完成后准备第二个动作。尽管感知和运动要求相匹配，但功能磁共振成像显示，在沿着顶内沟和腹侧视觉流的区域重叠条件下，大脑活动增加。多变量分析表明这些区域涉及刺激识别和行动选择。相比之下，已知参与计划即将到来的运动的背侧前运动皮层没有表现出明显的活动增强迹象。这一观察结果表明，同时动作执行和准备过程中的瓶颈出现在刺激识别和动作选择的层面上，而前运动皮层的运动规划可以与当前动作的执行同时展开，而不需要额外的神经活动。