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First published online June 16, 2005
Journal of Experimental Biology 208, 2539-2547 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01677

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Burst characteristics of daily jaw muscle activity in juvenile rabbits

T. van Wessel^1,*, G. E. J. Langenbach¹, N. Kawai², P. Brugman¹, E. Tanaka² and T. M. G. J. van Eijden¹

¹ Department of Functional Anatomy, Academic Centre for Dentistry Amsterdam (ACTA), Universiteit van Amsterdam and Vrije Universiteit, Meibergdreef 15, 1105 AZ, Amsterdam, The Netherlands
² Department of Orthodontics and Craniofacial Developmental Biology, Hiroshima University Graduate School of Biomedical Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan

View larger version (42K): [in a new window]   Fig. 1. Electrode locations and method of data analysis. (A) Implantation site of the transmitter in the neck area and locations of the electrodes in the five jaw muscles. (B) Examples of 5 min of simultaneously recorded EMG of three jaw muscles. (C) The enlargement (left) shows 1 s of muscle activity from the superficial masseter. The broken lines indicate the levels 5% and 50% of the peak-EMG. A burst was classified as a series of consecutive samples exceeding a predefined level of activity. The total number of bursts during 1 day was classified for muscle activities exceeding the 5% and 50% levels, which resulted in the distributions of burst number as a function of burst length (right). Note that the 5 min example (B) is not representative of the depicted distributions in C.

View larger version (33K): [in a new window]   Fig. 2. (A) Burst number, (B) mean burst length (s) and (C) duty time (%) for 1 day in week 9 (filled bars) and week 14 (open bars). Muscle activities exceeding 5%, 20%, 50% and 90% of the peak-EMG for all tested muscles are shown. Values are means ± S.D. Diga, digastric; Msan, superficial masseter; Mppo, posterior deep masseter; Ptm, medial pterygoid; Tem, temporalis. Asterisks indicate significant differences (P<0.05). Asterisks in A and C exceeding 50% and 90% indicate that the superficial masseter and medial pterygoid significantly differed from the digastric, deep masseter and temporalis.

View larger version (19K): [in a new window]   Fig. 3. Distributions of burst lengths of five jaw muscles averaged for all animals. Distributions show burst number as function of burst length for 1 day in week 9 (left) and week 14 (right) for muscle activities exceeding 5%, 20%, 50% and 90% of the peak-EMG. For clarity, only bursts up to 0.4 s are shown.