Modulation of spindle discharge from jaw-closing muscles during chewing foods of different hardness in awake rabbits

Hossain Md Zakir, Junichi Kitagawa, Yoshiaki Yamada, Masayuki Kurose, Rahman Md Mostafeezur, Kensuke Yamamura

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8 Scopus citations


The relationships between jaw-closing muscle spindle unit discharge and the hardness of foods were evaluated during chewing in awake rabbits. Spindle unit discharges recorded from the left mesencephalic trigeminal nucleus were correlated with the simultaneous recording of jaw movements and electromyographic (EMG) activities of the left masseter (jaw-closing) muscle during chewing soft and hard foods. A chewing cycle was divided into the fast-closing (FC), slow-closing (SC) and opening (OP) phases according to jaw movements. The chewing was classified as ipsilateral and contralateral chewing according to ipsilateral and contralateral to the recording side of the neuron, respectively. Spindle unit discharge was significantly higher during the FC and SC phases of the hard food than the soft food during both ipsilateral and contralateral chewing. The discharge was observed to be higher when the masseter muscle activity was higher. A comparison between the chewing sides reveals that the discharge was significantly higher during the slow-closing phase of ipsilateral chewing than contralateral chewing. From the above findings, the relationship of the spindle unit discharge with the hardness of foods was observed. Moreover, this relationship exists even when an animal chews food on the contralateral side suggesting the significance of the muscle spindle information for smooth chewing. In addition, the phase dependent difference of the spindle unit discharge between chewing sides suggests the distinct roles of the spindle information on the chewing and non-chewing sides.

Original languageEnglish (US)
Pages (from-to)380-386
Number of pages7
JournalBrain Research Bulletin
Issue number6
StatePublished - Nov 20 2010

Bibliographical note

Funding Information:
This work was supported by Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT) Grants-in-Aid for Scientific Research Kakenhi 18209056 and 21592354 . We thank Mr. Ito (Kameda Seika Co., Ltd.) for measuring fracture stress of food hardness.


  • Awake animal
  • Chewing phases
  • Chewing sides
  • Food
  • Muscle spindle


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