Yamaguchi Kaori, Nakamura Kimihiro, Oga Tatsuhide, Nakajima Yasoichi
National Rehabilitation Center for Persons with Disabilities, Research Institute, 4-1 Namiki, Tokorozawa 359-8555, Japan.
National Rehabilitation Center for Persons with Disabilities, Research Institute, 4-1 Namiki, Tokorozawa 359-8555, Japan; Human Brain Research Center, Kyoto University Graduate School of Medicine, 54 Shogoin, Kyoto 606-8507, Japan.
Neuropsychologia. 2014 Jul;59:142-7. doi: 10.1016/j.neuropsychologia.2014.05.003. Epub 2014 May 13.
There is increasing neuroimaging evidence suggesting that visually presented tools automatically activate the human sensorimotor system coding learned motor actions relevant to the visual stimuli. Such crossmodal activation may reflect a general functional property of the human motor memory and thus can be operating in other, non-limb effector organs, such as the orofacial system involved in eating. In the present study, we predicted that somatosensory signals produced by eating tools in hand covertly activate the neuromuscular systems involved in eating action. In Experiments 1 and 2, we measured motor evoked response (MEP) of the masseter muscle in normal humans to examine the possible impact of tools in hand (chopsticks and scissors) on the neuromuscular systems during the observation of food stimuli. We found that eating tools (chopsticks) enhanced the masseter MEPs more greatly than other tools (scissors) during the visual recognition of food, although this covert change in motor excitability was not detectable at the behavioral level. In Experiment 3, we further observed that chopsticks overall increased MEPs more greatly than scissors and this tool-driven increase of MEPs was greater when participants viewed food stimuli than when they viewed non-food stimuli. A joint analysis of the three experiments confirmed a significant impact of eating tools on the masseter MEPs during food recognition. Taken together, these results suggest that eating tools in hand exert a category-specific impact on the neuromuscular system for eating.
越来越多的神经影像学证据表明，视觉呈现的工具会自动激活人类感觉运动系统，该系统编码与视觉刺激相关的已学运动动作。这种跨模态激活可能反映了人类运动记忆的一般功能特性，因此可能在其他非肢体效应器官中起作用，比如参与进食的口面部系统。在本研究中，我们预测手持进食工具产生的体感信号会暗中激活参与进食动作的神经肌肉系统。在实验1和实验2中，我们测量了正常人类咬肌的运动诱发电位（MEP），以检验手持工具（筷子和剪刀）在观察食物刺激期间对神经肌肉系统可能产生的影响。我们发现，在视觉识别食物期间，进食工具（筷子）比其他工具（剪刀）更能增强咬肌的MEP，尽管这种运动兴奋性的暗中变化在行为水平上无法检测到。在实验3中，我们进一步观察到，总体而言筷子比剪刀更能增加MEP，并且当参与者观看食物刺激时，这种由工具驱动的MEP增加比观看非食物刺激时更大。对这三个实验的联合分析证实，在食物识别过程中，进食工具对咬肌MEP有显著影响。综上所述，这些结果表明手持进食工具对进食的神经肌肉系统有类别特异性影响。
