Center for Brain and Cognition, Pompeu Fabra University, Barcelona, 08018, Spain; Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, 04103, Germany; Department of Basic Sciences, Faculty of Medicine and Health Sciences, International University of Catalonia, 08195 Sant Cugat del Vallès, Spain.
Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, 04103, Germany; University Medical Center Hamburg-Eppendorf, 20246, Hamburg, Germany.
Neuroimage. 2018 Sep;178:721-734. doi: 10.1016/j.neuroimage.2018.05.032. Epub 2018 May 14.
The cerebral cortex modulates early sensory processing via feed-back connections to sensory pathway nuclei. The functions of this top-down modulation for human behavior are poorly understood. Here, we show that top-down modulation of the visual sensory thalamus (the lateral geniculate body, LGN) is involved in visual-speech recognition. In two independent functional magnetic resonance imaging (fMRI) studies, LGN response increased when participants processed fast-varying features of articulatory movements required for visual-speech recognition, as compared to temporally more stable features required for face identification with the same stimulus material. The LGN response during the visual-speech task correlated positively with the visual-speech recognition scores across participants. In addition, the task-dependent modulation was present for speech movements and did not occur for control conditions involving non-speech biological movements. In face-to-face communication, visual speech recognition is used to enhance or even enable understanding what is said. Speech recognition is commonly explained in frameworks focusing on cerebral cortex areas. Our findings suggest that task-dependent modulation at subcortical sensory stages has an important role for communication: Together with similar findings in the auditory modality the findings imply that task-dependent modulation of the sensory thalami is a general mechanism to optimize speech recognition.
大脑皮层通过反馈连接调节早期感觉处理，以作用于感觉通路核。这种自上而下的调制对人类行为的功能了解甚少。在这里，我们表明，视觉感觉丘脑（外侧膝状体，LGN）的自上而下的调制参与了视觉言语识别。在两项独立的功能磁共振成像（fMRI）研究中，与使用相同刺激材料进行面部识别所需的时间上更稳定的特征相比，当参与者处理视觉言语识别所需的快速变化的发音运动特征时，LGN 的反应增加。LGN 在视觉言语任务中的反应与参与者的视觉言语识别分数呈正相关。此外，任务相关的调制存在于言语运动中，而在涉及非言语生物运动的对照条件下则不会发生。在面对面交流中，视觉言语识别用于增强甚至实现对所说内容的理解。言语识别通常在专注于大脑皮层区域的框架中进行解释。我们的发现表明，在下丘脑感觉阶段的任务相关调制在交流中起着重要作用：与听觉模态中的类似发现一起，这些发现意味着感觉丘脑的任务相关调制是优化言语识别的一般机制。
