Unequivocally demonstrating the presence of multisensory signals at the earliest stages of cortical processing remains challenging in humans. In our study, we relied on the unique spatio-temporal resolution provided by intracranial stereotactic electroencephalographic (SEEG) recordings in patients with drug-resistant epilepsy to characterize the signal extracted from early visual (calcarine and pericalcarine) and auditory (Heschl's gyrus and planum temporale) regions during a simple audio-visual oddball task. We provide evidences that both cross-modal responses (visual responses in auditory cortex or the reverse) and multisensory processing (alteration of the unimodal responses during bimodal stimulation) can be observed in intracranial event-related potentials (iERPs) and in power modulations of oscillatory activity at different temporal scales within the first 150 msec after stimulus onset. The temporal profiles of the iERPs are compatible with the hypothesis that MSI occurs by means of direct pathways linking early visual and auditory regions. Our data indicate, moreover, that MSI mainly relies on modulations of the low-frequency bands (foremost the theta band in the auditory cortex and the alpha band in the visual cortex), suggesting the involvement of feedback pathways between the two sensory regions. Remarkably, we also observed high-gamma power modulations by sounds in the early visual cortex, thus suggesting the presence of neuronal populations involved in auditory processing in the calcarine and pericalcarine region in humans.

中文翻译：

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人体立体定向脑电图显示早期视觉和听觉皮层的多感官信号。

在人类皮层处理的最早阶段，毫无疑问地证明多感官信号的存在仍然具有挑战性。在我们的研究中，我们依靠耐药性癫痫患者的颅内立体定向脑电图（SEEG）记录提供的独特时空分辨率来表征从早期视觉（钙ar碱和黄ical子碱）和听觉（赫氏回旋和颞上叶）提取的信号）在一个简单的视听奇数球任务中的区域。我们提供的证据可以在颅内事件相关电位（iERPs）和振荡的功率调制中观察到交叉模态响应（听觉皮层或反向视觉响应）和多感觉处理（双模态刺激期间单模响应变化）。刺激发生后的最初150毫秒内，在不同的时间尺度上的活动。iERP的时间特征与MSI通过连接早期视觉和听觉区域的直接途径发生的假设相符。此外，我们的数据表明，MSI主要依赖于低频频段（听觉皮层中的theta频段和视觉皮层中的alpha频段）的调制，这暗示了两个感觉区域之间的反馈途径的参与。值得注意的是