Although it is well established that fronto-parietal regions are active during action observation, whether they play a causal role in the ability to infer others’ intentions from visual kinematics remains undetermined. In the experiments reported here, we combined offline continuous theta burst stimulation (cTBS) with computational modeling to reveal and causally probe single-trial computations in the inferior parietal lobule (IPL) and inferior frontal gyrus (IFG). Participants received cTBS over the left anterior IPL and the left IFG pars orbitalis in separate sessions before completing an intention discrimination task (discriminate intention of observed reach-to-grasp acts) or a kinematic discrimination task unrelated to intention (discriminate peak wrist height of the same acts). We targeted intention-sensitive regions whose fMRI activity, recorded when observing the same reach-to-grasp acts, could accurately discriminate intention. We found that transient disruption of activity of the left IPL, but not the IFG, impaired the observer’s ability to attribute intention to action. Kinematic discrimination unrelated to intention, in contrast, was largely unaffected. Computational analyses of how encoding (mapping of intention to movement kinematics) and readout (mapping of kinematics to intention choices) intersect at the single-trial level revealed that IPL cTBS did not diminish the overall sensitivity of intention readout to movement kinematics. Rather, it selectively misaligned intention readout with respect to encoding, deteriorating mapping from informative kinematic features to intention choices. These results provide causal evidence of how the left anterior IPL computes mapping from kinematics to intentions.

尽管额顶叶区域在动作观察过程中是活跃的，但它们是否在从视觉运动学推断他人意图的能力中发挥因果作用仍是未知数。在这里报告的实验中，我们将离线连续 theta 脉冲刺激 (cTBS) 与计算模型相结合，以揭示和因果探测下顶叶小叶 (IPL) 和下额叶回 (IFG) 的单次试验计算。参与者在左前 IPL 和左 IFG眶部接受 cTBS在完成意图辨别任务（辨别观察到的伸手抓握动作的意图）或与意图无关的运动辨别任务（辨别相同动作的峰值手腕高度）之前的单独会话中。我们针对意图敏感区域，其 fMRI 活动在观察相同的“伸手抓握”行为时记录，可以准确地区分意图。我们发现左侧 IPL 活动的短暂中断，而不是 IFG，削弱了观察者将意图归因于行动的能力。相比之下，与意图无关的运动歧视在很大程度上不受影响。编码（意图到运动运动学的映射）和读出（运动学到意图选择的映射）如何在单次试验级别相交的计算分析表明，IPL cTBS 并没有降低意图读数对运动运动学的整体敏感性。相反，它在编码方面选择性地错位了意图读出，恶化了从信息运动学特征到意图选择的映射。这些结果提供了左前 IPL 如何计算从运动学到意图的映射的因果证据。