title: Increased occlusal vertical dimension induces cortical plasticity in the rat face primary motor cortex.
abstract: Previous studies have demonstrated that functional plasticity in the primary motor cortex (M1) is related to motor-skill learning and changes in the environment. Increased occlusal vertical dimension (iOVD) may modulate mastication, such as in the masticatory cycle, and the firing properties of jaw-muscle spindles. However, little is known about the changes in motor representation within the face primary motor cortex (face-M1) after iOVD. The purpose of the present study was to determine the effect of iOVD on the face-M1 using intracortical microstimulation (ICMS). In an iOVD group, the maxillary molars were built-up by 2mm with acrylic. The electromyographic (EMG) activities from the left (LAD) and right (RAD) anterior digastric (AD), masseter and genioglossus (GG) muscles elicited by ICMS within the right face-M1 were recorded 1, 2 and 8 weeks after iOVD. IOVD was associated with a significant increase in the number of sites within the face-M1 from which ICMS evoked LAD and/or GG EMG activities, as well as a lateral shift in the center of gravity of the RAD and LAD muscles at 1 and 2 weeks, but not at 8 weeks. These findings suggest that a time-dependent neuroplastic change within the rat face-M1 occurs in association with iOVD. This may be related to the animal's ability to adapt to a change in the oral environment.
authors: Department of Orofacial Development and Function, Orthodontic Science, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, Japan. c.kato.orts@tmd.ac.jp
authors: C
authors: C
authors: Kato
authors: K
authors: K
authors: Fujita
authors: S
authors: S
authors: Kokai
authors: T
authors: T
authors: Ishida
authors: M
authors: M
authors: Shibata
authors: S
authors: S
authors: Naito
authors: T
authors: T
authors: Yabushita
authors: T
authors: T
authors: Ono
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001931:Brain Mapping; D004558:Electric Stimulation / Q000379:methods; D004576:Electromyography; D005145:Face / Q000294:innervation; D005152:Facial Muscles / Q000502:physiology*; D007839:Functional Laterality; D006112:Gravitation; D008297:Male; D009044:Motor Cortex / Q000166:cytology*; D009473:Neuronal Plasticity / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time; D014716:Vertical Dimension