Previous studies have demonstrated that auditory cortex activity can be influenced by cross-sensory visual inputs. Intracortical laminar recordings in nonhuman primates have suggested a feedforward (FF) type profile for auditory evoked but feedback (FB) type for visual evoked activity in the auditory cortex. To test whether cross-sensory visual evoked activity in the auditory cortex is associated with FB inputs also in humans, we analyzed magnetoencephalography (MEG) responses from eight human subjects (six females) evoked by simple auditory or visual stimuli. In the estimated MEG source waveforms for auditory cortex regions of interest, auditory evoked response showed peaks at 37 and 90 ms and visual evoked response at 125 ms. The inputs to the auditory cortex were modeled through FF- and FB-type connections targeting different cortical layers using the Human Neocortical Neurosolver (HNN), which links cellular- and circuit-level mechanisms to MEG signals. HNN modeling suggested that the experimentally observed auditory response could be explained by an FF input followed by an FB input, whereas the cross-sensory visual response could be adequately explained by just an FB input. Thus, the combined MEG and HNN results support the hypothesis that cross-sensory visual input in the auditory cortex is of FB type. The results also illustrate how the dynamic patterns of the estimated MEG source activity can provide information about the characteristics of the input into a cortical area in terms of the hierarchical organization among areas.

先前的研究表明，听觉皮层活动可能受到跨感官视觉输入的影响。非人类灵长类动物的皮质内层状记录表明，听觉皮层的听觉诱发活动为前馈（FF）型，而视觉诱发活动为反馈（FB）型。为了测试听觉皮层中的跨感官视觉诱发活动是否与人类的 FB 输入相关，我们分析了 8 名人类受试者（6 名女性）由简单的听觉或视觉刺激引起的脑磁图 (MEG) 反应。在估计的听觉皮层感兴趣区域的 MEG 源波形中，听觉诱发反应在 37 毫秒和 90 毫秒处显示峰值，视觉诱发反应在 125 毫秒处显示峰值。使用人类新皮质神经解算器 (HNN)，通过针对不同皮质层的 FF 和 FB 型连接对听觉皮层的输入进行建模，该神经解算器将细胞和电路级机制与 MEG 信号连接起来。 HNN 模型表明，实验观察到的听觉响应可以通过 FF 输入和 FB 输入来解释，而跨感官视觉响应可以仅通过 FB 输入来充分解释。因此，MEG 和 HNN 的组合结果支持听觉皮层中的跨感觉视觉输入是 FB 类型的假设。结果还说明了估计的 MEG 源活动的动态模式如何根据区域之间的层次结构提供有关皮质区域输入特征的信息。