Department of Psychology, University of Michigan, Ann Arbor, MI 48109, USA.
Multisens Res. 2024 Aug 16;37(4-5):341-363. doi: 10.1163/22134808-bja10129.
Congruent visual speech improves speech perception accuracy, particularly in noisy environments. Conversely, mismatched visual speech can alter what is heard, leading to an illusory percept that differs from the auditory and visual components, known as the McGurk effect. While prior transcranial magnetic stimulation (TMS) and neuroimaging studies have identified the left posterior superior temporal sulcus (pSTS) as a causal region involved in the generation of the McGurk effect, it remains unclear whether this region is critical only for this illusion or also for the more general benefits of congruent visual speech (e.g., increased accuracy and faster reaction times). Indeed, recent correlative research suggests that the benefits of congruent visual speech and the McGurk effect rely on largely independent mechanisms. To better understand how these different features of audiovisual integration are causally generated by the left pSTS, we used single-pulse TMS to temporarily disrupt processing within this region while subjects were presented with either congruent or incongruent (McGurk) audiovisual combinations. Consistent with past research, we observed that TMS to the left pSTS reduced the strength of the McGurk effect. Importantly, however, left pSTS stimulation had no effect on the positive benefits of congruent audiovisual speech (increased accuracy and faster reaction times), demonstrating a causal dissociation between the two processes. Our results are consistent with models proposing that the pSTS is but one of multiple critical areas supporting audiovisual speech interactions. Moreover, these data add to a growing body of evidence suggesting that the McGurk effect is an imperfect surrogate measure for more general and ecologically valid audiovisual speech behaviors.
一致的视觉语音会提高语音感知的准确性，尤其是在嘈杂的环境中。相反，不匹配的视觉语音会改变听到的内容，导致与听觉和视觉成分不同的错觉感知，这被称为麦格克效应。虽然之前的经颅磁刺激 (TMS) 和神经影像学研究已经确定左后颞上沟 (pSTS) 是产生麦格克效应的因果区域，但尚不清楚该区域是否仅对这种错觉至关重要，还是对更一般的一致视觉语音的好处至关重要（例如，提高准确性和更快的反应时间）。事实上，最近的相关研究表明，一致的视觉语音和麦格克效应的好处依赖于很大程度上独立的机制。为了更好地理解左 pSTS 如何因果地产生这些不同的视听整合特征，我们在受试者呈现一致或不一致（麦格克）视听组合时，使用单次 TMS 暂时中断该区域的处理。与过去的研究一致，我们观察到 TMS 对左 pSTS 的刺激降低了麦格克效应的强度。然而，重要的是，左 pSTS 刺激对一致的视听语音的积极益处（提高准确性和更快的反应时间）没有影响，这表明两个过程存在因果分离。我们的结果与提出 pSTS 只是支持视听语音相互作用的多个关键区域之一的模型一致。此外，这些数据增加了越来越多的证据表明，麦格克效应是更一般和更具生态有效性的视听语音行为的不完美替代测量。
