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A Short latency vestibulomasseteric reflex evoked by electrical stimulation over the mastoid in healthy humans

Deriu, Franca and Tolu, Eusebio and Rothwell, John C. (2003) A Short latency vestibulomasseteric reflex evoked by electrical stimulation over the mastoid in healthy humans. The Journal of Physiology, Vol. 553 (1), p. 267-279. eISSN 1469-7793. Article.

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DOI: 10.1113/jphysiol.2003.047274


We describe EMG responses recorded in active masseter muscles following unilateral and bilateral electrical vestibular stimulation (EVS, current pulses of 5 mA intensity, 2 ms duration, 3 Hz frequency). Averaged responses in unrectified masseter EMG induced by unilateral EVS were examined in 16 healthy subjects; effects induced by bilateral (transmastoid) stimulation were studied in 10 subjects. Results showed that unilateral as well as bilateral EVS induces bilaterally a clear biphasic response (onset latency ranging from 7.2 to 8.8 ms), that is of equal amplitude and latency contra- and ipsilateral to the stimulation site. In all subjects, unilateral cathodal stimulation induced a positive-negative response termed p11/n15 according to its mean peak latency; the anodal stimulation induced a response of opposite polarity (n11/p15) in 11/16 subjects. Cathodal responses were significantly larger than anodal responses. Bilateral stimulation induced a p11/n15 response significantly larger than that induced by the unilateral cathodal stimulation. Recordings from single motor units showed that responses to cathodal stimulation corresponded to a brief (2-4 ms) silent period in motor unit discharge rate. The magnitude of EVS-induced masseter response was linearly related to current intensity and scaled with the mean level of EMG activity. The size of the p11/n15 response was asymmetrically modulated when subjects were tilted on both sides; in contrast head rotation did not exert any influence. Control experiments excluded a possible role of cutaneous receptors in generating the masseter response. We conclude that transmastoid electrical stimulation evokes vestibulomasseteric reflexes in healthy humans at latencies consistent with a di-trisynaptic pathway.

Item Type:Article
ID Code:625
Uncontrolled Keywords:Masseter muscles, vestibular stimulation, vestibulomasseteric reflex, humans
Subjects:Area 05 - Scienze biologiche > BIO/09 Fisiologia
Divisions:001 Università di Sassari > 01 Dipartimenti > Scienze biomediche
Publisher:The Physiological Society, Blackwell Publishing
Deposited On:18 Aug 2009 10:02

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