title: The influence of the asymmetric tonic neck reflex on the H-reflex in human temporal muscle.
abstract: In contrast to limb muscles, little is known about the role of the asymmetric tonic neck reflex (ATNR) on jaw-elevator muscles. The effect of rotation of the head on the H-reflex in the anterior part of the temporal muscle after masseteric nerve stimulation was evaluated. Eight healthy volunteers (7 males and 1 female, age range 18 to 27 years, mean age 22 years) participated. The masseteric M-response and the masseteric and temporal H-reflexes were elicited by stimulating the masseteric nerve using a monopolar needle technique. The electromyographic activity of the muscles was recorded by surface electrodes. The ATNR was modified by changing position of the head: 30 degrees rotation towards the stimulated side (+N), 30 degrees rotation towards the non-stimulated side (-N) and 0 degree central position (C). The heteronymous temporal H-reflex was elicited at a stimulus intensity of 120% maximal M-response at a frequency of 1 Hz, in random series of 5 to 20 sweeps, up to 30-50 sweeps for each position. On-line averaging was performed. A significant reduction of the H-reflex amplitude was observed in the -N position (p-0.02 paired "t"-test, p = 0.015 Wilcoxon signed rank test), while a significant increase was present in the +N position (p = 0.007 PTT and WSR). Also multivariate analysis yielded a significant influence of head rotation on H-reflex amplitude (p = 0.0032). It can be concluded that the ATNR has a significant influence on the H-reflex of the human temporal muscle.
authors.affiliation: Istituto di Clinica Odontoiatrica, Università degli Studi, Parma.
authors.forename: G M
authors.initials: GM
authors.lastname: Macaluso
authors.forename: A D
authors.initials: AD
authors.lastname: De Laat
authors.forename: G
authors.initials: G
authors.lastname: Pavesi
mesh_terms: D000293:Adolescent; D000328:Adult; D004558:Electric Stimulation; D004576:Electromyography; D005260:Female; D006181:H-Reflex / Q000502:physiology*; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D015999:Multivariate Analysis; D009333:Neck / Q000502:physiology*; D012016:Reference Values; D012018:Reflex / Q000502:physiology*; D012399:Rotation; D018709:Statistics, Nonparametric; D013703:Temporal Muscle / Q000502:physiology*