Schepers Inga M, Yoshor Daniel, Beauchamp Michael S
Department of Neurobiology and Anatomy, University of Texas Medical School at Houston, Houston, TX, USA Current Address: Department of Psychology, Oldenburg University, Oldenburg, Germany.
Department of Neurosurgery, Baylor College of Medicine, Houston, TX, USA.
Cereb Cortex. 2015 Nov;25(11):4103-10. doi: 10.1093/cercor/bhu127. Epub 2014 Jun 5.
Human speech contains both auditory and visual components, processed by their respective sensory cortices. We test a simple model in which task-relevant speech information is enhanced during cortical processing. Visual speech is most important when the auditory component is uninformative. Therefore, the model predicts that visual cortex responses should be enhanced to visual-only (V) speech compared with audiovisual (AV) speech. We recorded neuronal activity as patients perceived auditory-only (A), V, and AV speech. Visual cortex showed strong increases in high-gamma band power and strong decreases in alpha-band power to V and AV speech. Consistent with the model prediction, gamma-band increases and alpha-band decreases were stronger for V speech. The model predicts that the uninformative nature of the auditory component (not simply its absence) is the critical factor, a prediction we tested in a second experiment in which visual speech was paired with auditory white noise. As predicted, visual speech with auditory noise showed enhanced visual cortex responses relative to AV speech. An examination of the anatomical locus of the effects showed that all visual areas, including primary visual cortex, showed enhanced responses. Visual cortex responses to speech are enhanced under circumstances when visual information is most important for comprehension.
人类语音包含听觉和视觉成分，由各自的感觉皮层进行处理。我们测试了一个简单的模型，其中与任务相关的语音信息在皮层处理过程中得到增强。当听觉成分无信息时，视觉语音最为重要。因此，该模型预测，与视听（AV）语音相比，视觉皮层对纯视觉（V）语音的反应应该增强。我们记录了患者在感知纯听觉（A）、V和AV语音时的神经元活动。视觉皮层对V和AV语音的高伽马波段功率有强烈增加，而阿尔法波段功率有强烈下降。与模型预测一致，V语音的伽马波段增加和阿尔法波段下降更强。该模型预测，听觉成分的无信息性质（而不仅仅是其缺失）是关键因素，我们在第二个实验中对此进行了测试，在该实验中，视觉语音与听觉白噪声配对。正如预测的那样，与AV语音相比，带有听觉噪声的视觉语音显示出增强的视觉皮层反应。对效应的解剖学位置的检查表明，包括初级视觉皮层在内的所有视觉区域都显示出增强的反应。当视觉信息对理解最为重要时，视觉皮层对语音的反应会增强。
