Hosack Victoria B, Arce-McShane Fritzie I
Department of Oral Health Sciences, School of Dentistry, University of Washington, Seattle, WA.
Division of Neuroscience, Washington National Primate Research Center, University of Washington, Seattle, WA.
bioRxiv. 2024 Jul 4:2024.07.02.601741. doi: 10.1101/2024.07.02.601741.
Directional tongue movements are essential for vital behaviors, such as feeding and speech, to position food for chewing and swallowing safely and to position the tongue for accurate sound production. While directional tuning has been well-studied in the arm region of the sensorimotor cortex during reaching tasks, little is known about how 3D tongue direction is encoded in the orofacial region during natural behaviors. Understanding how tongue direction is represented in the brain has important implications for improving rehabilitation for people with orolingual dysfunctions. The goal of this study is to investigate how 3D direction of tongue movement is encoded in the orofacial sensorimotor cortex (OSMCx) during feeding and drinking, and how this process is affected by the loss of oral sensation. Using biplanar video-radiography to track implanted markers in the tongue of behaving non-human primates (), 3D positional data was recorded simultaneously with spiking activity in primary motor (MIo) and somatosensory (SIo) areas of the orofacial cortex using chronically implanted microelectrode arrays. In some sessions, tasks were preceded by bilateral nerve block injections to the sensory branches of the trigeminal nerve. Modulation to the 3D tongue direction was found in a majority of MIo but not SIo neurons during feeding, while the majority of neurons in both areas were modulated to the direction of tongue protrusion during drinking. Following sensory loss, the proportion of directionally tuned neurons decreased and shifts in the distribution of preferred direction were observed in OSMCx neurons. Overall, we show that 3D directional tuning of MIo and SIo to tongue movements varies with behavioral tasks and availability of sensory information.
定向舌运动对于诸如进食和说话等重要行为至关重要，它能将食物定位以便安全咀嚼和吞咽，并将舌头定位以便准确发声。虽然在伸手够物任务期间，感觉运动皮层的手臂区域的定向调谐已得到充分研究，但在自然行为期间，关于三维舌方向如何在口面部区域编码却知之甚少。了解舌方向在大脑中如何表征对于改善口颌功能障碍患者的康复具有重要意义。本研究的目的是调查在进食和饮水期间，舌运动的三维方向如何在口面部感觉运动皮层（OSMCx）中编码，以及这个过程如何受到口腔感觉丧失的影响。使用双平面视频放射成像来跟踪行为中的非人灵长类动物舌头中植入的标记物，利用长期植入的微电极阵列，在口面部皮层的初级运动（MIo）和体感（SIo）区域记录三维位置数据的同时记录神经元放电活动。在一些实验中，在任务之前对三叉神经的感觉分支进行双侧神经阻滞注射。在进食期间，在大多数MIo神经元而非SIo神经元中发现了对三维舌方向的调制，而在饮水期间，两个区域的大多数神经元都被调制到舌突出方向。感觉丧失后，方向调谐神经元比例下降，并且在OSMCx神经元中观察到偏好方向分布的变化。总体而言，我们表明MIo和SIo对舌运动的三维定向调谐随行为任务和感觉信息的可用性而变化。
