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Nagarajan A, Sinha SK. Masseter Vestibular evoked myogenic potentials: A new tool to assess the vestibulomasseteric reflex pathway. J Otol 2024; 19:46-54. [PMID: 38313757 PMCID: PMC10837556 DOI: 10.1016/j.joto.2023.12.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 11/20/2023] [Accepted: 12/21/2023] [Indexed: 02/06/2024] Open
Abstract
Purpose This review article provides the readers with an in-depth insight in understanding and interpreting various research literatures on the masseter vestibular evoked myogenic potentials (mVEMP). The article also reviews the contemporary researches involving the clinical applications of the mVEMP. Conclusions Masseter VEMP is an evolving yet clinically promising neuro-otology test tool that has recently gained more research interest and is considered an additional tool to diagnose various vestibular disorders. Masseter VEMP assesses the functional integrity of the acoustic-masseteric and vestibulo-masseteric reflex pathways. The mVEMP could be used as a complementary test to evaluate the same peripheral generator as the cervical VEMP but a different central pathway i.e., vestibulo-trigeminal pathway. Various research studies that have experimented on parameters such as the effect of different electrode montages (zygomatic vs mandibular configurations), stimulation rates, filter settings and stimuli used to evoke mVEMP have been discussed in this article that could assist in the optimization of a comprehensive clinical protocol. The latency and the amplitude of mVEMP waveforms serve as significant parameters in differentiating normals from those of the clinical populations. Along with the cVEMPs and oVEMPs, mVEMP might help diagnose brainstem lesions in REM Sleep behaviour disorders, Multiple Sclerosis and Parkinson's disease. However, further studies are required to probe in this area of research.
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Chen Y, Gong X, Ibrahim SIA, Liang H, Zhang J. Convergent innervations of mesencephalic trigeminal and vestibular nuclei neurons onto oculomotor and pre-oculomotor neurons-Tract tracing and triple labeling in rats. PLoS One 2022; 17:e0278205. [PMID: 36441755 PMCID: PMC9704657 DOI: 10.1371/journal.pone.0278205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Accepted: 11/13/2022] [Indexed: 11/29/2022] Open
Abstract
In studies of vestibulo-ocular reflex (VOR), the horizontal VOR circuit is much clearer than vertical-torsional VOR. The circuit and mechanism of gravity-related vertical-torsional VOR is probably weak. "Somatosensory vestibular interaction" is a known extra source to facilitate VOR, and cervico-ocular reflex is a representative for torsional VOR compensation. Whereas, how the cervical afferents finally reach the oculomotor system is less documented. Actually, when the head tilts, which generates cervico-ocular reflex, not only the neck muscle is activated, but also the jaw muscle is stretched by gravity dragged mandible and/or tissue-muscle connection between the mandible and clavicle. We have previously identified a projection from the jaw muscle afferent mesencephalic trigeminal nucleus (Vme) neurons to oculomotor nuclei (III/IV) and their premotor neurons in interstitial nucleus of Cajal (INC)-a well-known pre-oculomotor center manipulating vertical-torsional eye movements. We hypothesized that these projections may interact with vestibulo-ocular signals during vertical-torsional VOR, because effects of gravity on jaw muscles and bones has been reported. Thus, we injected different anterograde tracers into the Vme and medial vestibular nucleus (MVN)-the subnuclear area particularly harboring excitatory vestibulo-ocular neurons, and immunostained III/IV motoneurons. Retrograde tracer was injected into the III in the same animals after dual anterograde tracers' injections. Under confocal microscope, we observed the Vme and MVN neuronal endings simultaneously terminated onto the same III/IV motoneurons and the same INC pre-oculomotor neurons. We consider that jaw muscle proprioceptive Vme neurons projecting to the III/IV and INC would sense spindle activity if the jaw muscle is stretched by gravity dragged mandible or connection between mandible and clavicle during head rolling. Therefore, the convergent innervation of the Vme and MVN neurons onto the oculomotor and pre-oculomotor nuclei would be a neuroanatomic substrate for interaction of masticatory proprioception with the vestibulo-ocular signals upon the oculomotor system during vertical-torsional VOR.
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Affiliation(s)
- Yongmei Chen
- Department of Central Laboratory, Hubei University of Art and Science Medical Center, Xiangyang City, Hubei, China
- Institute of Neuroscience, Xiangyang Central Hospital, Affiliation of Hubei University of Art and Science, Xiangyang City, Hubei, China
| | - Xinrui Gong
- Institute of Neuroscience, Xiangyang Central Hospital, Affiliation of Hubei University of Art and Science, Xiangyang City, Hubei, China
- Department of Anesthesiology, Xiangyang Central Hospital, Affiliation of Hubei University of Art and Science, Xiangyang City, Hubei, China
- * E-mail: (XG); (JZ)
| | - Shaimaa I. A. Ibrahim
- Institute of Neuroscience, Xiangyang Central Hospital, Affiliation of Hubei University of Art and Science, Xiangyang City, Hubei, China
- Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
| | | | - Jingdong Zhang
- Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
- Xi’an BRIGHT Eye Hospital, Xi’an, Shaanxi, China
- * E-mail: (XG); (JZ)
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Thirusangu VP, Sinha SK. Effect of Electrode Montage on 500-Hz Tone Burst Evoked Masseter Vestibular Evoked Myogenic Potential. Am J Audiol 2022; 31:403-410. [PMID: 35537126 DOI: 10.1044/2022_aja-22-00016] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
PURPOSE Masseter vestibular evoked myogenic potentials (VEMPs) are short-latency myogenic responses obtained in response to electric or acoustic stimulation. It is a relatively newer test that helps assess the vestibulo-trigeminal pathway, thereby gaining more interest in brainstem pathologies like Parkinsonism, multiple sclerosis, and idiopathic random eye movement disorders. The purpose of the study was to compare the effect of zygomatic versus mandibular reference montage on the latency and amplitude of masseter VEMP (mVEMP) using a 500-Hz tone burst stimulus. METHOD Twenty healthy participants in the age range of 18-29 years, with no complaints of vestibular signs and symptoms, were recruited for the study. VEMP was recorded for all the participants using 500-Hz tone burst stimuli in zygomatic electrode montage and mandibular electrode montage. mVEMP was recorded in both ipsilateral and contralateral modes. RESULTS The Wilcoxon signed-ranks test revealed no significant difference between the zygomatic and mandibular montage for both the latency and amplitude parameters (p > .05). CONCLUSIONS This study revealed no significant difference in p11 and n21 latencies as well as p11-n21 rectified amplitude between zygomatic and mandibular montage using a 500-Hz tone burst stimulus in young adults. Hence, utilizing a 500-Hz tone burst, mVEMP can be recorded in zygomatic and mandibular electrode montage.
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Affiliation(s)
| | - Sujeet Kumar Sinha
- Department of Audiology, All India Institute of Speech and Hearing, Mysuru
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Romero DJ, Jacobson GP, Roberts RA. The effect of EMG magnitude on the masseter vestibular evoked myogenic potential (mVEMP). J Otol 2022; 17:203-210. [PMID: 36249925 PMCID: PMC9547109 DOI: 10.1016/j.joto.2022.06.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 06/15/2022] [Accepted: 06/16/2022] [Indexed: 10/26/2022] Open
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The vestibulo-masseteric reflex and the acoustic-masseteric reflex: a reliability and responsiveness study in healthy subjects. Exp Brain Res 2020; 238:1769-1779. [PMID: 32280998 DOI: 10.1007/s00221-020-05804-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 04/04/2020] [Indexed: 10/24/2022]
Abstract
The vestibulo-masseteric reflex (VMR or p11 wave), the acoustic-masseteric reflex (AMR or p1/n21 wave) and the mixed vestibulo-cochlear p11/n21 potential are responses of masseter muscles to sound that can be employed to evaluate brainstem function. This study was aimed at establishing the test-retest reliability and responsiveness of these reflex parameters according to the type of electrode configuration. Twenty-two healthy volunteers (M:F = 11:11; mean age 25.3 ± 5.2 years) participated in two testing sessions separated by one week. Zygomatic and mandibular montages were compared following unilateral and bilateral stimulations. For reliability purposes, intraclass correlation coefficient (ICC), coefficient of variation of the method error (CVME) and standard error of measurement (SEM) were calculated. The minimal detectable difference (MDD) was also determined as a measure of responsiveness. Both VMR (p11 wave) and AMR could be consistently evoked from test to retest, although the frequency rate was significantly higher (all p values ≤ 0.009) with zygomatic (VMR: 97.7-100%; AMR: 86.9-97.6%) than mandibular montage (VMR: 84.7-89.8%; AMR: 65.0-67.8%), with no significant differences between unilateral and bilateral stimulations. Good-to-excellent reliability and responsiveness (high ICC, low CVME, SEM and MDD scores) were detected for corrected amplitudes and peak latencies for all reflex responses, whereas raw amplitudes were associated to poor reliability. The reliability of the zygomatic montage proved superior to the mandibular montage for all reflex responses. Given their high test-retest consistency and capability to study different features of the reflex arch, both peak latencies and corrected amplitudes should be reported and considered in the interpretation of reflex testing results.
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De Natale E, Ginatempo F, Mercante B, Manca A, Magnano I, Ortu E, Pilurzi G, Melis F, Rothwell J, Deriu F. Vestibulo masseteric reflex and acoustic masseteric Reflex. Normative data and effects of age and gender. Clin Neurophysiol 2019; 130:1511-1519. [DOI: 10.1016/j.clinph.2019.05.021] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Revised: 04/17/2019] [Accepted: 05/03/2019] [Indexed: 12/13/2022]
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Birinyi A, Rácz N, Kecskes S, Matesz C, Kovalecz G. Neural circuits underlying jaw movements for the prey-catching behavior in frog: distribution of vestibular afferent terminals on motoneurons supplying the jaw. Brain Struct Funct 2017; 223:1683-1696. [PMID: 29189907 DOI: 10.1007/s00429-017-1581-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 11/25/2017] [Indexed: 10/18/2022]
Abstract
Coordinated movement of the jaw is essential for catching and swallowing the prey. The majority of the jaw muscles in frogs are supplied by the trigeminal motoneurons. We have previously described that the primary vestibular afferent fibers, conveying information about the movements of the head, established close appositions on the motoneurons of trigeminal nerve providing one of the morphological substrates of monosynaptic sensory modulation of prey-catching behavior in the frog. The aim of our study was to reveal the spatial distribution of vestibular close appositions on the somatodendritic compartments of the functionally different trigeminal motoneurons. In common water frogs, the vestibular and trigeminal nerves were simultaneously labeled with different fluorescent dyes and the possible direct contacts between vestibular afferents and trigeminal motoneurons were identified with the help of DSD2 attached to an Andor Zyla camera. In the rhombencephalon, an overlapping area was detected between the incoming vestibular afferents and trigeminal motoneurons along the whole extent of the trigeminal motor nucleus. The vestibular axon collaterals formed large numbers of close appositions with dorsomedial and ventrolateral dendrites of trigeminal motoneurons. The majority of direct contacts were located on proximal dendritic segments closer than 300 µm to the somata. The identified contacts were evenly distributed on rostral motoneurons innervating jaw-closing muscles and motoneurons supplying jaw-opening muscles and located in the caudal part of trigeminal nucleus. We suggest that the identified contacts between vestibular axon terminals and trigeminal motoneurons may constitute one of the morphological substrates of a very quick response detected in trigeminal motoneurons during head movements.
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Affiliation(s)
- András Birinyi
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Nagyerdei krt. 98, Debrecen, 4032, Hungary.
| | - Nóra Rácz
- Department of Pediatric Dentistry and Orthodontics, Faculty of Dentistry, University of Debrecen, Nagyerdei krt. 98, Debrecen, 4032, Hungary
| | - Szilvia Kecskes
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Nagyerdei krt. 98, Debrecen, 4032, Hungary
| | - Clara Matesz
- Department of Pediatric Dentistry and Orthodontics, Faculty of Dentistry, University of Debrecen, Nagyerdei krt. 98, Debrecen, 4032, Hungary.,MTA-DE Neuroscience Research Group, University of Debrecen, Nagyerdei krt. 98, Debrecen, 4032, Hungary.,Department of Oral Anatomy, Faculty of Dentistry, University of Debrecen, Nagyerdei krt. 98, Debrecen, 4032, Hungary
| | - Gabriella Kovalecz
- Department of Pediatric Dentistry and Orthodontics, Faculty of Dentistry, University of Debrecen, Nagyerdei krt. 98, Debrecen, 4032, Hungary
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Treffel L, Dmitrieva L, Gauquelin-Koch G, Custaud MA, Blanc S, Gharib C, Millet C. Craniomandibular System and Postural Balance after 3-Day Dry Immersion. PLoS One 2016; 11:e0150052. [PMID: 26913867 PMCID: PMC4767814 DOI: 10.1371/journal.pone.0150052] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 02/09/2016] [Indexed: 12/30/2022] Open
Abstract
The objective of the study was to determine the influence of simulated microgravity by exposure to dry immersion on the craniomandibular system. Twelve healthy male volunteers participated in a 3-day dry immersion study. Before and immediately after exposure we measured maximal bite force using piezoresistive sensors. The mechanical properties of the jaw and cervical muscles were evaluated before, during, and after dry immersion using MyotonPRO. Because recent studies reported the effects of jaw motor activity on the postural stability of humans, stabilometric measurements of center of pressure were performed before and after dry immersion in two mandibular positions: rest position without jaw clenching, and intercuspidal position during voluntary teeth clenching. Results revealed no significant changes of maximal bite force after dry immersion. All postural parameters were significantly altered by dry immersion. There were however no significant differences in stabilometric data according to mandibular position. Moreover the masseter tonicity increased immediately after the end of dry immersion period. Dry immersion could be used as a valid model for studying the effects of microgravity on human subjects. However, 3 days appear insufficient in duration to evaluate the effects of weightlessness on maximal bite force. Our research suggests a link between postural disturbance after dry immersion and masseter tonicity.
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Affiliation(s)
- Loïc Treffel
- Université Claude Bernard Lyon 1, Lyon, France
- Université de Strasbourg, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7178, Strasbourg, France
| | - Liubov Dmitrieva
- Institute of Biomedical Problems, Moscow, Russia
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 6214 - Institut National de la Santé et de la Recherche Médicale 1083, Université d’Angers, Angers, France
| | | | - Marc-Antoine Custaud
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 6214 - Institut National de la Santé et de la Recherche Médicale 1083, Université d’Angers, Angers, France
- Centre de Recherche Clinique, Centre Hospitalo-Universitaire d’Angers, Angers, France
| | - Stéphane Blanc
- Université de Strasbourg, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7178, Strasbourg, France
| | - Claude Gharib
- Université Claude Bernard Lyon 1, Lyon, France
- Centre International d’Ostéopathie, Saint-Etienne, France
| | - Catherine Millet
- Université Claude Bernard Lyon 1, Lyon, France
- Service d’Odontologie, Hospices Civils de Lyon, Lyon, France
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Inokuchi H, González-Fernández M, Matsuo K, Brodsky MB, Yoda M, Taniguchi H, Okazaki H, Hiraoka T, Palmer JB. Electromyography of Swallowing with Fine Wire Intramuscular Electrodes in Healthy Human: Amplitude Difference of Selected Hyoid Muscles. Dysphagia 2015; 31:33-40. [PMID: 26487062 DOI: 10.1007/s00455-015-9655-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Accepted: 10/03/2015] [Indexed: 11/27/2022]
Abstract
Few studies have examined the intensity of muscle activity during swallowing in healthy humans. We examined selected hyoid muscles using fine wire intramuscular electromyography (EMG) during swallowing of four food consistencies. Thirteen healthy adults were studied using videofluorography and EMG of the anterior belly of digastric (ABD), geniohyoid (GH), sternohyoid (SH), and masseter (MA; surface electrodes) while ingesting thin liquid (three trials) and solid food of three consistencies (banana, tofu, and cookie, three trials each). After rectification, integration, and normalization, peak EMG amplitudes for each muscle in each trial were measured. Hyoid displacements were measured in two dimensions. Data were analyzed using repeated measures ANOVA with Bonferroni correction. GH had the highest adjusted amplitude for both solids and liquid. For MA and ABD, amplitude was highest with triturated cookie. For ABD, amplitude was lowest with liquid. There were no significant food consistency effects for GH or SH. Hyoid displacements were greatest for cookie and the lowest for liquid. EMG amplitude varied with initial food consistency. The high peak EMG amplitude of GH is consistent with its essential role in opening the upper esophageal sphincter. High MA amplitude with hard solid foods is likely due to the higher tongue-palate pressure with triturated solids. The higher ABD amplitude with solid food is associated with greater hyoid displacement. These findings support the existence of a central pattern generator that modifies the level of muscle activity during pharyngeal swallowing in response to input from mechanoreceptors in the oral cavity.
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Affiliation(s)
- Haruhi Inokuchi
- Department of Physical Medicine and Rehabilitation, Johns Hopkins University School of Medicine, Baltimore, MD, USA. .,Department of Rehabilitation Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
| | - Marlís González-Fernández
- Department of Physical Medicine and Rehabilitation, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Koichiro Matsuo
- Department of Physical Medicine and Rehabilitation, Johns Hopkins University School of Medicine, Baltimore, MD, USA.,Department of Dentistry, Fujita Health University, Toyoake, Aichi, Japan
| | - Martin B Brodsky
- Department of Physical Medicine and Rehabilitation, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Mitsumasa Yoda
- Department of Physical Medicine and Rehabilitation, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Hiroshige Taniguchi
- Department of Physical Medicine and Rehabilitation, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Hideto Okazaki
- Department of Physical Medicine and Rehabilitation, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Takashi Hiraoka
- Department of Physical Medicine and Rehabilitation, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Jeffrey B Palmer
- Department of Physical Medicine and Rehabilitation, Johns Hopkins University School of Medicine, Baltimore, MD, USA.,Department of Otolaryngology-Head and Neck Surgery and Center for Functional Anatomy and Evolution, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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Reflex responses of masseter muscles to sound. Clin Neurophysiol 2010; 121:1690-9. [DOI: 10.1016/j.clinph.2009.11.093] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2009] [Revised: 10/19/2009] [Accepted: 11/09/2009] [Indexed: 11/18/2022]
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Deriu F, Ortu E, Capobianco S, Giaconi E, Melis F, Aiello E, Rothwell JC, Tolu E. Origin of sound-evoked EMG responses in human masseter muscles. J Physiol 2007; 580:195-209. [PMID: 17234698 PMCID: PMC2075422 DOI: 10.1113/jphysiol.2006.123240] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Sound is a natural stimulus for both cochlear and saccular receptors. At high intensities it evokes in active masseter muscles of healthy subjects two overlapping reflexes: p11/n15 and p16/n21 waves, whose origin has not yet been demonstrated. Our purpose was to test which receptor in the inner ear is responsible for these reflexes. We compared masseter EMG responses induced in normal subjects (n = 9) by loud clicks (70-100 dB normal hearing level (NHL), 0.1 ms, 3 Hz) to those evoked in subjects with a selective lesion of the cochlea (n = 5), of the vestibule (n = 1) or with mixed cochlear-vestibular failure (n = 5). In controls, 100 dB clicks induced bilaterally, in the unrectified mean EMG (unrEMG), a clear p11 wave followed by a less clear n15 wave and a subsequent n21 wave. Lowering the intensity to 70 dB clicks abolished the p11/n15 wave, while a p16 wave appeared. Rectified mean EMG (rectEMG) showed, at all intensities, an inhibitory deflection corresponding to the p16/n21 wave in the unrEMG. Compared to controls, all deaf subjects had a normal p11 wave, together with more prominent n15 wave; however, the p16/n21 waves, and their corresponding inhibition in the rectEMG, were absent. The vestibular patient had bilaterally clear p11 waves only when 100 dB clicks were delivered bilaterally or to the unaffected ear. Stimulation of the affected ear induced only p16/n21 waves. Data from mixed patients were consistent with those of deaf and vestibular patients. We conclude that click-induced masseter p11/n15 waves are vestibular dependent, while p16/n21 waves depend on cochlear integrity.
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Affiliation(s)
- Franca Deriu
- Department of Biomedical Sciences, Section of Human Physiology and Bioengineering, Viale San Pietro 43/b, 07100--Sassari, Italy.
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Cuccurazzu B, Deriu F, Tolu E, Yates BJ, Billig I. A monosynaptic pathway links the vestibular nuclei and masseter muscle motoneurons in rats. Exp Brain Res 2007; 176:665-71. [PMID: 17216144 PMCID: PMC2684793 DOI: 10.1007/s00221-006-0834-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2006] [Accepted: 12/13/2006] [Indexed: 10/23/2022]
Abstract
Physiological evidence indicates that vestibular signals modulate the activity of motoneurons innervating the masseter muscle. Recently, experiments using transynaptic retrograde transport of pseudorabies virus provided anatomical evidence that many neurons concentrated in the dorsomedial part of the parvicellular division of the medial vestibular nucleus (MVePC) and the caudal prepositus hypoglossi (PH) provide inputs to motoneurons innervating the lower third of the superficial layer of the masseter muscle. However, it was not clear whether this vestibulo-trigeminal projection was monosynaptic or polysynaptic. The present study sought to determine whether neurons in the MVePC or PH project directly to motoneurons controlling the masseter muscle in rats. For this purpose, an anterograde tracer (biotinylated dextran amine, BDA) was injected into vestibular nuclei (mainly MVePC) or PH and a retrograde tracer (the beta-subunit of cholera toxin, b-CT) was injected into the masseter muscle ipsilateral or contralateral to the BDA injection site. Following injections of BDA into the vestibular nuclei or PH, anterogradely labeled axon terminals were observed bilaterally in the motor trigeminal nucleus (Mo5), particularly in the ventral, medial, and lateral portions of the nucleus; projections to dorsal Mo5 were sparse. In addition, retrogradely labeled motoneurons were located in the ventral and lateral portions of the ipsilateral Mo5. Moreover, anterogradely labeled terminals were observed to be in close proximity to motoneurons in the Mo5 that were retrogradely labeled from b-CT injections into the masseter muscle. This study provides direct evidence that a monosynaptic pathway exists between the MVePC and PH and masseter motoneurons.
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Affiliation(s)
- B Cuccurazzu
- Department of Otolaryngology, Eye and Ear Institute, School of Medicine, University of Pittsburgh, PA 15213, USA
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13
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Giaconi E, Deriu F, Tolu E, Cuccurazzu B, Yates BJ, Billig I. Transneuronal tracing of vestibulo-trigeminal pathways innervating the masseter muscle in the rat. Exp Brain Res 2005; 171:330-9. [PMID: 16307240 PMCID: PMC2396390 DOI: 10.1007/s00221-005-0275-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2005] [Accepted: 10/19/2005] [Indexed: 11/26/2022]
Abstract
Previous studies reported that the activity of trigeminal motoneurons innervating masseter muscles is modulated by vestibular inputs. We performed the present study to provide an anatomical substrate for these physiological observations. The transynaptic retrograde tracer pseudorabies virus-Bartha was injected into multiple sites of the lower third of the superficial layer of the masseter muscle in rats, a subset of which underwent a sympathectomy prior to virus injections, and the animals were euthanized 24-120 h later. Labeled masseteric motoneurons were first found in the ipsilateral trigeminal motor nucleus following a 24-h postinoculation period; subsequent to 72-h survival times, the number of infected motoneurons increased, and at > or =96 h many of these cells showed signs of cytopathic changes. Following 72-h survival times, a few transynaptically labeled neurons appeared bilaterally in the medial vestibular nucleus (MVe) and the caudal prepositus hypoglossi (PH) and in the ipsilateral spinal vestibular nucleus (SpVe). At survival times of 96-120 h, labeled neurons were consistently observed bilaterally in all vestibular nuclei (VN), although the highest concentration of infected cells was located in the caudal part of the MVe, the SpVe, and the caudal portion of PH. The distribution and density of labeling in the VN and PH were similar in sympathectomized and nonsympathectomized rats. These anatomical data provide the first direct evidence that neurons in the VN and PH project bilaterally to populations of motoneurons innervating the lower third of the superficial layer of the masseter muscle. The MVe, PH, and SpVe appear to play a predominant integrative role in producing vestibulo-trigeminal responses.
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Affiliation(s)
- E Giaconi
- Department of Otolaryngology, Eye and Ear Institute, University of Pittsburgh, Room 519, Pittsburgh, PA 15213, USA
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Deriu F, Tolu E, Rothwell JC. A Sound-Evoked Vestibulomasseteric Reflex in Healthy Humans. J Neurophysiol 2005; 93:2739-51. [PMID: 15601734 DOI: 10.1152/jn.01005.2004] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Averaged responses to loud clicks were recorded in the unrectified and rectified masseter electromyogram (EMG) of 18 healthy subjects. Unilateral clicks (0.1 ms, 3 Hz, 70–100 dB NHL), delivered during a steady masseter contraction, evoked bilateral responses that appeared to consist of 2 components on the basis of threshold, latency, and their appearance in rectified EMG. The lowest threshold response appeared as a p16 wave (onset 11–13 ms) in the unrectified EMG and corresponded with a 10- to 12-ms period of inhibition in the rectified EMG. Higher-intensity clicks recruited an earlier p11 response in the unrectified EMG (onset 7.0–9.2 ms) that sometimes appeared as an initial increase in the rectified EMG before suppression. The amplitude of the p11 wave scaled with background EMG level and was asymmetrically modulated by 30° tilt of the whole body. The threshold of the early p11/n15 wave in masseter was the same as the threshold for click-induced vestibulocollic reflexes. Single motor unit recordings demonstrated that responses in masseters corresponded to a silent period in unit firing that began earlier and lasted longer at 100 dB than at 80 dB. We propose that loud clicks induce 2 partially overlapping short-latency reflexes in masseter muscle EMG: a p11/n15 response, which we suggest is of vestibular origin, and a p16/n21 response, which we suggest is equivalent to the previously described jaw–acoustic reflex.
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Affiliation(s)
- Franca Deriu
- Department of Biomedical Sciences, Section of Human Physiology and Bioengineering, University of Sassari, Italy.
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Deriu F, Tolu E, Rothwell JC. A short latency vestibulomasseteric reflex evoked by electrical stimulation over the mastoid in healthy humans. J Physiol 2003; 553:267-79. [PMID: 12949229 PMCID: PMC2343496 DOI: 10.1113/jphysiol.2003.047274] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
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.
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Affiliation(s)
- Franca Deriu
- Department of Biomedical Sciences, Section of Human Physiology and Bioengineering, University of Sassari, Sassari, Italy.
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Abstract
External loads arising as a result of the orientation of body segments relative to gravity can affect the achievement of movement goals. The degree to which subjects adjust control signals to compensate for these loads is a reflection of the extent to which forces affecting motion are represented neurally. In the present study we assessed whether subjects, when speaking, compensate for loads caused by the orientation of the head relative to gravity. We used a mathematical model of the jaw to predict the effects of control signals that are not adjusted for changes to head orientation. The simulations predicted a systematic change in sagittal plane jaw orientation and horizontal position resulting from changes to the orientation of the head. We conducted an empirical study in which subjects were tested under the same conditions. With one exception, empirical results were consistent with the simulations. In both simulation and empirical studies, the jaw was rotated closer to occlusion and translated in an anterior direction when the head was in the prone orientation. When the head was in the supine orientation, the jaw was rotated away from occlusion. The findings suggest that the nervous system does not completely compensate for changes in head orientation relative to gravity. A second study was conducted to assess possible changes in acoustical patterns attributable to changes in head orientation. The frequencies of the first (F1) and second (F2) formants associated with the steady-state portion of vowels were measured. As in the kinematic study, systematic differences in the values of F1 and F2 were observed with changes in head orientation. Thus the acoustical analysis further supports the conclusion that control signals are not completely adjusted to offset forces arising because of changes in orientation.
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