Direct electrical stimulation (DES) is used to perform functional brain mapping during awake surgery and in epileptic patients. DES may be coupled with the measurement of Evoked Potentials (EP) to study the conductive and integrative properties of activated neural ensembles and probe the spatiotemporal dynamics of short- and long-range networks. However, its electrophysiological effects remain by far unknown. We recorded ECoG signals on two patients undergoing awake brain surgery and measured EP on functional sites after cortical stimulations and were the firsts to record three different types of EP on the same patients. Using low-intensity (1–3 mA) to evoke electrogenesis we observed that: (i) “true” remote EPs are attenuated in amplitude and delayed in time due to the divergence of white matter pathways; (ii) “false” remote EPs are attenuated but not delayed: as they originate from the same electrical source; (iii) Singular but reproducible positive components in the EP can be generated when the DES is applied in the temporal lobe or the premotor cortex; and (iv) rare EP can be triggered when the DES is applied subcortically: these can be either negative, or surprisingly, positive. We proposed different activation and electrophysiological propagation mechanisms following DES, based on the nature of activated neural elements and discussed important methodological pitfalls when measuring EP in the brain. Altogether, these results pave the way to map the connectivity in real-time between the DES and the recording sites; to characterize the local electrophysiological states and to link electrophysiology and function. In the future, and in practice, this technique could be used to perform electrophysiological mapping in order to link (non)-functional to electrophysiological responses with DES and could be used to guide the surgical act itself.

在清醒手术期间和癫痫患者中，直接电刺激（DES）用于执行功能性大脑映射。DES可能与诱发电位（EP）的测量相结合，以研究活化神经集合体的传导和整合特性，并探讨短程和远程网络的时空动态。但是，其电生理作用仍然是未知的。我们记录了两名接受清醒脑外科手术的患者的ECoG信号，并在皮层刺激后在功能部位测量了EP，并且首次在同一患者中记录了三种不同类型的EP。使用低强度（1-3 mA）诱发电发生，我们观察到：（i）由于白质途径的差异，“真正的”远程EP的振幅减弱，时间延迟；（ii）“虚假”的远程EP衰减但没有延迟：因为它们来自同一电源；（iii）当在颞叶或运动前皮层中使用DES时，EP中会产生奇异但可重现的阳性成分；（iv）皮下应用DES时，可能触发稀有EP：它们可以是负值，也可以是令人惊讶的正值。基于激活的神经元的性质，我们提出了遵循DES的不同激活和电生理传播机制，并讨论了测量大脑中EP时的重要方法陷阱。总而言之，这些结果为在DES和记录站点之间实时映射连通性铺平了道路。表征局部电生理状态，并将电生理与功能联系起来。在未来，在实践中，