Eating tools in hand activate the brain systems for eating action: a transcranial magnetic stimulation study.
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.
National Rehabilitation Center for Persons with Disabilities, Research Institute, 4-1 Namiki, Tokorozawa 359-8555, Japan. Electronic address: yamaguchi-kaori@rehab.go.jp.
Kaori
K
Yamaguchi
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.
Kimihiro
K
Nakamura
Toranomon Hospital Kajigaya Department of Rehabilitation, 1-3-1 Kajigaya, Takatsu-ku, Kawasaki, Kanagawa 213-8587, Japan.
Tatsuhide
T
Oga
National Rehabilitation Center for Persons with Disabilities, Research Institute, 4-1 Namiki, Tokorozawa 359-8555, Japan.
Yasoichi
Y
Nakajima
D000328:Adult; D001921:Brain / Q000502:physiology*; D004576:Electromyography; D019054:Evoked Potentials, Motor; D005247:Feeding Behavior / Q000502:physiology*; D005260:Female; D006225:Hand / Q000502:physiology*; D006801:Humans; D007600:Judgment / Q000502:physiology; D008297:Male; D008406:Masseter Muscle / Q000502:physiology*; D009043:Motor Activity / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D010364:Pattern Recognition, Visual / Q000502:physiology; D010812:Physical Stimulation; D011930:Reaction Time; D012660:Semantics; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
Eating action; Masseter muscles; Motor-evoked potential (MEP); Sensorimotor; Transcranial magnetic stimulation (TMS)