title: Effects of cortical activations on enhancement of handgrip force during teeth clenching: an fMRI study.
abstract: We assessed the effect of teeth clenching on handgrip force behaviorally, and investigated cortical activity during the occurrence of facilitatory effects using functional magnetic resonance imaging (fMRI). Twenty-three participants were assessed as to whether they had habitual teeth clenching during maximal voluntary contraction (MVC) exertion, and 21 of them were identified to have such a habit. For those participants, behavioral testing showed that MVC with clenching was greater compared with without clenching (approximately 108% greater on average). Next, cortical activity was measured under gripping with clenching (GwC), gripping without clenching (GwoC), and teeth clenching (C) conditions. We found that the activity of the hand region in primary motor cortex (M1), cingulate motor area/supplementary motor area (CMA/SMA) and anterior cerebellum (AC) was greater in contrast of GwC vs. (GwoC+C). Furthermore, significant correlation was observed between the increasing ratio of the handgrip force and the % signal change in the hand region of M1 and AC, but not in CMA/SMA. These results suggest that the activation in the hand region of M1 and AC may facilitate the spinal motoneurons, and the activation in the hand region in M1 by clenching may be due to a signal from CMA/SMA.
authors: Maxillofacial Orthognathics, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan; Global Center of Excellence (GCOE) Program, International Research Center for Molecular Science in Tooth and Bone Diseases, Tokyo, Japan. Electronic address: n-kawakubo.mort@tmd.ac.jp.
authors: Naomi
authors: N
authors: Kawakubo
authors: Maxillofacial Orthognathics, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan; Global Center of Excellence (GCOE) Program, International Research Center for Molecular Science in Tooth and Bone Diseases, Tokyo, Japan. Electronic address: mjmort@tmd.ac.jp.
authors: Jun J
authors: JJ
authors: Miyamoto
authors: Cognitive Neurobiology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan; The Center for Brain Integration Research, Tokyo Medical and Dental University, Tokyo, Japan. Electronic address: katz.cnb@tmd.ac.jp.
authors: Narumi
authors: N
authors: Katsuyama
authors: Orthodontic Science, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan. Electronic address: t.ono.orts@tmd.ac.jp.
authors: Takashi
authors: T
authors: Ono
authors: Oral and Maxillofacial Radiology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan; Oral and Maxillofacial Radiology, Graduate School, University of Tokushima, Tokushima, Japan. Electronic address: honda@dent.tokushima-u.ac.jp.
authors: Ei-Ichi
authors: E
authors: Honda
authors: Oral and Maxillofacial Radiology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan. Electronic address: kura.orad@tmd.ac.jp.
authors: Tohru
authors: T
authors: Kurabayashi
authors: Cognitive Neurobiology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan; The Center for Brain Integration Research, Tokyo Medical and Dental University, Tokyo, Japan. Electronic address: masato.cnb@tmd.ac.jp.
authors: Masato
authors: M
authors: Taira
authors: Maxillofacial Orthognathics, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan; Global Center of Excellence (GCOE) Program, International Research Center for Molecular Science in Tooth and Bone Diseases, Tokyo, Japan. Electronic address: k-moriyama.mort@tmd.ac.jp.
authors: Keiji
authors: K
authors: Moriyama
mesh_terms: D000328:Adult; D001732:Bite Force; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D002531:Cerebellum / Q000502:physiology; D005260:Female; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009044:Motor Cortex / Q000502:physiology; D014836:Volition / Q000502:physiology
keywords: Cerebellum; Handgrip; Human; Motor cortex; Teeth clench; fMRI