AI 中文总结
该研究发现对视觉运动区V5/MT施加抑制性TMS会减弱视觉言语识别中LGN的反应调节及V5/MT与LGN的功能连接，证实皮层-丘脑反馈是视觉加工的重要机制。
AI 中文摘要
感觉丘脑核的反应会受到知觉任务的调节，这种反应调节是否依赖于人类大脑皮层的反馈机制尚不明确。本研究在视觉言语识别的背景下探讨该问题：视觉感觉丘脑即外侧膝状体（LGN），对视觉言语任务的BOLD反应与非言语对照任务存在差异。我们测试这种反应调节是否依赖于视觉联合皮层，特别是视觉运动区V5/MT的功能。对26名健康成人的双侧视觉运动敏感区V5/MT施加抑制性经颅磁刺激（TMS），随后在功能磁共振成像（fMRI）期间，让参与者观看相同的静音人脸视频，分别完成视觉言语识别任务和颜色识别任务。以顶点刺激作为主动对照区域，结果显示，在顶点刺激后，LGN在视觉言语任务与颜色任务之间表现出显著的信号变化；而在抑制性V5/MT刺激后，这种调节作用显著减弱。V5/MT刺激还降低了V5/MT与LGN之间的任务依赖性功能连接。这些结果表明，皮层-丘脑反馈是视觉加工的重要机制，特别是视觉联合皮层在言语识别过程中对LGN反应的调节具有因果作用。
英文摘要
Responses in the sensory thalamic nuclei are modulated by perceptual tasks. Whether such response modulations rely on feedback from cerebral cortex in humans is unknown. Here, we addressed this question in the context of visual speech recognition: the visual sensory thalamus, i.e. the lateral geniculate nucleus (LGN), has differential BOLD-responses to visual speech than non-speech control tasks. We tested whether such response modulation relies on the function of the visual association cortex, specifically visual-motion area V5/MT. We applied inhibitory transcranial magnetic stimulation (TMS) over bilateral visual-motion sensitive areas V5/MT on 26 healthy adults. Subsequently, participants performed a visual speech and a colour recognition task on identical muted videos of speaking faces during functional magnetic resonance imaging (fMRI). The LGN showed a significant signal change between the visual speech task and the colour task following Vertex stimulation as active control region. This modulation was significantly reduced following inhibitory V5/MT stimulation. V5/MT stimulation also reduced task-dependent functional connectivity between V5/MT and the LGN. These results identify corticothalamic feedback as integral mechanism in visual processing. In particular, the visual association cortex has a causal role in modulating LGN responses during speech recognition.
