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PubMed2003

Evidence of an influence of asymmetrical occlusal interferences on the activity of the sternocleidomastoid muscle.

To investigate the hypothesis of a functional coupling between occlusion and neck muscles, the immediate effect of asymmetrical occlusal interferences on the pattern of contraction of the sternocleidomastoid muscles (SCM) during maximum voluntary clench (MVC) was analysed in 30 healthy subjects. All subjects had a complete and sound permanent dentition, without temporomandibular joint (TMJ) and craniocervical disorders. A 5-s surface electromyogram (EMG) examination of the SCM was performed during (1) MVC in intercuspal position and (2) MVC with a single 200-microm occlusal interference alternatively positioned on teeth 16, 13, 23, 26. All subjects had a symmetrical EMG activity during MVC in intercuspal position. For each subject, SCM potentials were standardized as percentage of the mean potentials recorded during the MVC on natural dentition and the EMG waves of left- and right-side muscles were compared by computing the relevant percentage overlapping coefficient (POC). For each subject, the best and the worst POCs computed during the four MVC tests with occlusal interferences were found and the percentage difference between them was calculated. In the four MVC tests with occlusal interferences, SCM symmetry was very different from that recorded during MVC on natural dentition. The difference between the best and worst POCs computed within each subject was very variable, ranging from 1.52 to 41.57%. In conclusion, when young healthy subjects with a normal occlusion clench on an asymmetrical occlusal interference, they have an altered left-right side pattern of contraction of their SCM. In almost all subjects, a previously symmetrical pattern became asymmetrical.

Adult↗

PubMed1987

Cross-correlation of EMG reveals widespread synchronization of motor units during some slow movements in intact cats.

It is commonly assumed that the motor units comprising a single mammalian muscle will be recruited asynchronously at subtetanic firing rates to produce smoothly modulated force output. However, electromyograms from certain neck muscles, recorded by implanted bipolar "patch" electrodes having large contacts, often exhibited a rhythmic clustering of spike activity whose patterns suggested that motor-unit firing was synchronized both within and across muscles. We have developed a computerized processing system that digitizes EMG activity and calculates auto- and cross-correlation products of selected segments. The presence or absence of synchronization caused by neural mechanisms can be identified and differentiated from that due to the rhythmicity of the behavior itself (e.g. shaking) or due to cross-talk, according to the shapes of the resultant correlograms. These methods have so far been applied to the study of hindlimb and neck muscle EMG during various natural motor behaviors, but they provide a general, quantitative tool for the study of an important aspect of motor control that may be overlooked by conventional sampling and smoothing techniques.

Animals↗

PubMed2002

Neck motor unit activities induced by inputs from periodontal mechanoreceptors in rats.

Clinical evidence suggests that head movements may be coupled with oro-facial functions, which are predominantly controlled by somatosensory inputs from the oro-facial area. However, the effects of specific modalities of sensory inputs on the neck muscles' motor activity are still unclear. In the present study, natural pressure stimulation was applied to the rat's upper first molars, while motor unit electromyographic activity was recorded from the dorsal neck splenius muscle. During the hold phase of pressure stimulation, clear tonic discharges were elicited in the splenius muscles on both sides. Mean threshold values were 622.3 mN (+/- 19.6 SEM, n = 39) and 496.8 mN (+/- 26.4 SEM, n = 43) for ipsi- and contralateral sides, respectively (p < 0.001, Mann-Whitney U test). Analysis of our data suggests that periodontal inputs may play an important role in controlling the motor activity of neck muscles, in addition to its well-known coordination of the masticatory function.

Analysis of Variance↗

PubMed1998

Decrease in gastric sensitivity to distension by 5-HT1A receptor agonists in rats.

Using an in vivo model for evaluation of gastric sensitivity in awake rats, we aimed to determine whether 5-hydroxytryptamine 1A (5-HT1A) agonists modify pain threshold and gastric compliance specifically through 5-HT1A receptors. Isobaric gastric distensions were performed with a barostat using steps of 5 mm Hg in male rats equipped with a gastric balloon and electrodes implanted in the neck muscles. Gastric distension at 15 or 20 mm Hg induced a typical posture associated with contractions of the neck muscles. Rats received drugs 30 min before gastric distension. The 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), administered intraperitoneally (0.5 mg/kg) increased gastric pain threshold and gastric tone. These effects were reproduced when administered centrally (0.05 mg/kg) and blocked by intracerebroventricular administration of the 5-HT1A antagonist WAY 100635. Flesinoxan (4 mg/kg, intraperitoneally), another 5-HT1A agonist reproduced the effects of 8-OH-DPAT on pain threshold and gastric tone and the alpha2-receptor antagonist yohimbine did not modify the action of 8-OH-DPAT. Our results indicate that activation of 5-HT1A receptors at the level of the central nervous system increases gastric tone and decreases gastric sensitivity to distension.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed1986

Organization of motor pools supplying the cervical musculature in a cryptodyran turtle, Pseudemys scripta elegans. II. Medial motor nucleus and muscles supplied by two motor nuclei.

In this paper we describe the medial motor nucleus of Pseudemys cervical spinal cord and the motor pools of three neck muscles that exhibit an unusual pattern of innervation. Cells of the medial motor nucleus form a longitudinal column at the dorsomedial gray/white border of the ventral horn from C1 through C8. In Nissl-stained transverse sections they appear fusiform with prominent medially projecting dendrites; in HRP material these dendrites are seen to cross into the contralateral ventral funiculus. Medial nuclear cells vary in size (12-31 micron in diameter) and are often relatively large (greater than 21 micron in diameter). They are significantly larger and more numerous in caudal than in rostral cervical segments. Medial nuclear cells supply three of the cervical muscles examined in this study: mm. retrahens capitis collique (RCCQ), testocervicis, and longus colli. These three muscles differ from other cervical muscles in Pseudemys and from vertebrate limb muscles in that they are supplied in parallel by two populations of motor neurons: the medial and ventral motor nuclei (cf. Yeow and Peterson, '86). Ventral nuclear cells supplying these three muscles are organized into a musculotopic pattern with m. testocervicis motor neurons most medial and m. RCCQ motor neurons lateral; in contrast, the location of medial nuclear motor neurons is invariant with respect to muscle position. HRP-positive medial nuclear cells are sometimes smaller (m. testocervicis) but more often are as large or larger (mm. RCCQ and longus colli) than ventral nuclear cells supplying the same muscles, thus suggesting that they supply extrafusal muscle fibers, perhaps different muscle unit types in the three muscles. Based on the morphology of medial nuclear cells and the probable actions of the muscles they innervate, we hypothesize that the medial motor nucleus may represent a discrete functional system for producing bilaterally synchronous muscle activation, and that this system is accessed by a subset of muscles in the cervical complex.

Animals↗

PubMed2005

Gender differences in pain modulation evoked by repeated injections of glutamate into the human trapezius muscle.

Gender differences in pain habituation, temporal summation, and pressure hyperalgesia evoked by repeated injections of glutamate into the dominant trapezius muscle were investigated. The glutamate-evoked muscle pain intensity and pressure pain threshold (PPT) were assessed. The PPTs were measured bilaterally in the trapezius muscles (local pain area) and posterolateral neck muscles (referred pain area) after glutamate injection in healthy and age-matched males and females (each n=14). Two glutamate injections (0.4 ml, 2M each) were injected with an interval of 5 min. One injection of glutamate (0.4 ml, 2M) served as a control. Males, but not females, rated the second injection (maximal pain intensity) significantly less painful than the first injection. The area under the visual analogue scale pain curve of the second injection was significantly larger than the first injection in females. Repeated glutamate injections, but not one-glutamate injection, significantly decreased PPTs in the local pain area, with no significant gender differences. No PPTs changes were observed either in the contralateral trapezius muscle or bilaterally in the referred pain areas in either sex. These results suggest that a less efficient pain habituation and a greater susceptibility to the development of temporal summation of muscle pain in females, but not in males, might be one of the contributing factors to the higher incidence of neck shoulder pain in females. In addition, the reduction of PPTs in the local pain area evoked by intramuscular glutamate injection may represent an early process of peripheral pressure hyperalgesia, which is most likely gender independent.

Adult↗

PubMed1997

Nitric oxide synthase (NOS) I during postnatal development in rat and mouse skeletal muscle.

Previous studies on adult rat and mouse skeletal muscles have shown the spatial association of nitric oxide synthase (NOS) I to the dystrophin complex (DC) in the sarcolemma of type II fibers and, in combination with the NMDA receptor-1 (NMDAR-1), an accumulation of the enzyme at the neuromuscular junctions (NMJ) of this fiber type. Using immunohistochemistry, enzyme histochemistry and alpha-bungarotoxin labeling we report here temporal relationships of NOS I, members of the DC, other components of the cortical cytoskeleton in the junctional and non-junctional sarcolemma as well as of molecules involved in NMJ transmission of either type I or II myofibers especially in head and neck muscles during postnatal rat and mouse development. Fiber typing was performed by specific anti-myosin antibodies. Beginning with postnatal day (PD) 1 in both fiber types dystrophin, dystrophin-associated glycoproteins (DAG), beta-dystroglycan, alpha-sarcoglycan (adhalin) and spectrin were present in the junctional and extrajunctional sarcolemma, while utrophin, acetylcholinesterase, alpha-bungarotoxin labeled acetylcholine receptors were concentrated in the NMJ of both fiber types. NOS I activity and immunoreactivity were only found in the NMJ region of type II fibers, where NMDAR-1 appeared around PD 15. Primarily in the tongue there was no strict correlation between muscle fiber type and NOS I behaviour during early postnatal development, and muscle fibers not reactive for myosin antibodies against both fiber types were negative or positive for NOS I but always positive for the other molecules either in both the junctional and extrajunctional sarcolemma or in the NMJ only; later all muscle fibers of the tongue were of type II and NOS I-positive. Maturation of enzyme activities, immunoreactivities and AChR intensity depended on the respective muscle and can last until PD 50; in the tongue and neck muscles they appeared to increase approximately until PD 20 or 25. In conclusion, in type II fibers of rat and mouse skeletal muscle all molecules with the exception of NMDAR-1 and relevant for NOS I targeting and positioning as well as function inside and outside the NMJ are already present at birth, but their concentrations and/or activities increase postnatally, and the adult situation appears to be reached between the third and seventh week of postnatal life. Therefore, initial interactions between NOS I and the other molecules necessary for the formation of the NOS I-DC in and on the way to the sarcolemma presumably take place before birth.

Animals↗

PubMed1988

Models of sensorimotor transformations and vestibular reflexes.

The vestibulo-ocular and vestibulo-collic reflexes are well-studied sensorimotor systems with dynamic properties that have been successfully modeled. Recently proposed matrix and tensorial models attempt to describe the spatial organization of these reflexes in three dimensions. Here we describe experiments that test these models. We show that a matrix model of the vestibulo-ocular reflex provides a satisfactory description of its spatial properties. The vestibulo-collic reflex is more complex, but a tensorial model makes close predictions of neck muscle excitation by the vestibulo-collic reflex. In addition, our preliminary data show that the cervico-collic or neck stretch reflex produces essentially the same spatial pattern of neck muscle excitation as the vestibulo-collic reflex, a finding predicted by the tensorial model. We conclude by showing electromyographic and single neuron responses that can be modeled only by combining models of dynamics with models of spatial organization. We believe that the development of such models is the next major challenge in the application of quantitative methods to analysis of reflex behavior.

Animals↗

PubMed2002

Disturbed jaw behavior in whiplash-associated disorders during rhythmic jaw movements.

As shown previously, "functional jaw movements" are the result of coordinated activation of jaw as well as neck muscles, leading to simultaneous movements in the temporomandibular, atlanto-occipital, and cervical spine joints. In this study, the effect of neck trauma on natural jaw function was evaluated in 12 individuals suffering from whiplash-associated disorders (WAD). Spatiotemporal characteristics of mandibular and concomitant head movements were evaluated for three different modes of rhythmic jaw activities: self-paced continuous maximal jaw-opening/-closing movements, paced continuous maximal jaw-opening/-closing movements at 50 cycles/minute, and unilateral chewing. Compared with healthy subjects, the WAD group showed smaller magnitude and altered coordination pattern (a change in temporal relations) of mandibular and head movements. In conclusion, these results show that neck trauma can derange integrated jaw and neck behavior, and underline the functional coupling between the jaw and head-neck motor systems.

Adult↗

PubMed1977

Possible subdivisions among alpha-adrenoreceptors in various isolated tissues.

The ratio (expressed in log10 units) of the equieffective concentrations of (+)- and (-)-noradrenaline has been measured in a variety of isolated tissues in the presence of cocaine (1 x 10(-5) M), tropolone (3 x 10(-5) M) and (+/-)-propranolol (5 x 10(-7) to 5 x 10(-5) M). The values obtained fall into 3 distinct and statistically different groups. Firstly, a high group comprising (mean +/- s.e.) mouse vasdeferens (2-78 +/- 0-04), rabbit duodenum (2-91 +/- 0-07) and ileum (2-86 +/- 0-05). Secondly a middle group comprising rabbit vas deferens (2-54 +/- 0-04), bladder neck muscle (2-56 +/- 0-07) and spleen 2-50 +/- 0-02), guinea-pig vas deferens (2-55 +/- 0-10) and bladder neck muscle (2-48 +/- 0-13) and rat deferens (2-40 +/- 0-08) and thirdlya low group comprising the bladder detrusor muscle from both the rabbit (2-08 +/- 0-08) and the guinea-pig (2-07 +/- 0-04). Under the same conditions measurement of pA2 values for phentolamine and piperoxan against noradrenaline gave the following values in rat vase deferens (8-22 +/- 0-07 and 6-72 +/- 0-03 respectively) and mouse vas deferens (8-31 +/- 0-05 and 6-53 +/- 0-07 respectively). The results are discussed in relation to other findings conderning the nature of the alpha-adrenoreceptor in these tissues. In spite of the absence of any significant difference between the potency of the alpha-adrenoreceptor blocking agents in the two species it is suggested that alpha-adernoreceptors may not belong to a single homogenous population but may vary in their characteristics from tissue to tissue.

Adrenergic alpha-Antagonists↗

PubMed1983

Visual evoked potentials to light flash in cats: is a frontal sinus reference electrode truly indifferent?

In flaxedilized cats, visual cortex evoked potentials (VEPs) to an intensity series of brief light flashes were recorded differentially using either a screw over frontal sinus or an insect pin in neck muscle as the reference electrode. At the same time EPs from the cornea (the ERG) and frontal sinus were recorded differentially against the neck muscle electrode. The EP recorded from the frontal sinus screw was a miniature of the ERG recorded from the cornea, with the same latencies and shape as the ERG but only 10-30% of its amplitude. At a fast presentation rate (1/sec) the amplitude of the ERG, and consequently the frontal sinus potential, decreased with increasing intensity of light flash, whereas at a slow presentation rate (1/3 or 1/5 sec) the ERG and frontal sinus potential increased in response to all but the highest intensities. The location of the reference electrode and the rate of light flash presentation had the following effects on visual cortex EP amplitudes. A frontal sinus reference increased the amplitudes of early components (less than 100 msec) of the VEP. Also, VEP amplitudes as a function of flash intensity yielded slopes which tended to be positive at a slow presentation rate and negative at a fast presentation rate. This effect is in accord with the rate dependent slopes of the frontal sinus potential.

Animals↗

PubMed1996

Coding of peripersonal space in inferior premotor cortex (area F4).

1. We studied the functional properties of neurons in the caudal part of inferior area 6 (area F4) in awake monkeys. In agreement with previous reports, we found that the large majority (87%) of neurons responded to sensory stimuli. The responsive neurons fell into three categories: somatosensory neurons (30%); visual neurons (14%); and bimodal, visual and somatosensory neurons (56%). Both somatosensory and bimodal neurons typically responded to light touch of the skin. Their RFs were located on the face, neck, trunk, and arms. Approaching objects were the most effective visual stimuli. Visual RFs were mostly located in the space near the monkey (peripersonal space). Typically they extended in the space adjacent to the tactile RFs. 2. The coordinate system in which visual RFs were coded was studied in 110 neurons. In 94 neurons the RF location was independent of eye position, remaining in the same position in the peripersonal space regardless of eye deviation. The RF location with respect to the monkey was not modified by changing monkey position in the recording room. In 10 neurons the RF's location followed the eye movements, remaining in the same retinal position (retinocentric RFs). For the remaining six neurons the RF organization was not clear. We will refer to F4 neurons with RF independent of eye position as somatocentered neurons. 3. In most somatocentered neurons (43 of 60 neurons) the background level of activity and the response to visual stimuli were not modified by changes in eye position, whereas they were modulated in the remaining 17. It is important to note that eye deviations were constantly accompanied by a synergic increase of the activity of the ipsilateral neck muscles. It is not clear, therefore, whether the modulation of neuron discharge depended on eye position or was a consequence of changes in neck muscle activity. 4. The effect of stimulus velocity (20-80 cm/s) on neuron response intensity and RF extent in depth was studied in 34 somatocentered neurons. The results showed that in most neurons the increase of stimulus velocity produced an expansion in depth of the RF. 5. We conclude that space is coded differently in areas that control somatic and eye movements. We suggest that space coding in different cortical areas depends on the computational necessity of the effectors they control.

Animals↗

PubMed1998

Concomitant mandibular and head-neck movements during jaw opening-closing in man.

To test the hypothesis of a functional relationship between the human mandibular and cranio-cervical motor systems, head-neck movements during voluntary mandibular movements were studied in 10 healthy young adults, using a wireless optoelectronic system for three-dimensional (3D) movement recording. The subjects, unaware of the underlying aim of the study, were instructed to perform maximal jaw opening-closing tasks at fast and slow speed. Movements were quantified as 3D movement amplitudes. A consistent finding in all subjects was parallel and coordinated head-neck movements during both fast and slow jaw opening-closing tasks. Jaw opening was always accompanied by head-neck extension and jaw closing by head-neck flexion. Combined movement and electromyographic recordings showed concomitant neck muscle activity during head-neck movements, indicative of an active repositioning of the head. No differences in 3D movement amplitudes could be seen with respect to speed. The head movement was 50% of the mandibular movement during jaw opening, but significantly smaller (30-40%), during the jaw closing phase. In repeated tests, the 3D movement amplitudes of the concomitant head movements were less variable during slow jaw movement and during the jaw opening phase, than during fast and jaw closing movements, suggesting speed- and phase-related differences in the mechanisms controlling the integrated mandibular and head-neck motor acts. The present results give further support to the concept of a functional trigeminocervical coupling during jaw activities in man.

Adult↗

PubMed1999

Case report of malocclusion with abnormal head posture and TMJ symptoms.

Abnormal cervical muscle function can cause abnormal head posture, adversely affecting the development and morphology of the cervical spine and maxillofacial skeleton, which in turn leads to facial asymmetry and occlusal abnormality. There can be morphologic abnormalities of the mandibular fossa, condyle, ramus, and disk accompanying the imbalance of the cervical and masticatory muscles activities. Two normally growing Japanese female patients with Class II Division 1 malocclusion presented with TMJ symptoms and poor head posture as a result of abnormal sternocleidomastoid and trapezius cervical muscle activities. One patient underwent tenotomy of the two heads of the sternocleidomastoid muscle and the other patient did not. In addition to orthodontics, the 2 patients received physiotherapy of the cervical muscles during treatment. Both were treated with a functional appliance as a first step, followed by full multi-bracketed treatment to establish a stable form of occlusion and to improve facial esthetics with no head gear. This interdisciplinary treatment approach resulted in normalization of stomatognathic function, elimination of TMJ symptoms, and improvement of facial esthetics. In the growing patients, the significant response of the fossa, condyle, and ramus on the affected side during and after occlusal correction contributed to the improvement of cervical muscle activity. Based on the result, early occlusal improvement, combined with orthopedic surgery of the neck muscles or physiotherapy to achieve muscular balance of the neck and masticatory muscles, was found to be effective. Two patients illustrate the potential for promoting symmetric formation of the TMJ structures and normal jaw function, with favorable effects on posttreatment growth of the entire maxillofacial skeleton.

Birth Injuries↗

PubMed1986

Segmental projection from muscle spindles: a perspective from the upper cervical spinal cord.

The segmental connections of muscle spindle afferents originating from primary endings do not follow the same pattern at all levels of the spinal cord. This review is concerned with the characteristics of neck muscle spindle projections, which illustrate several differences between their segmental organization and the arrangement of hindlimb muscle spindle afferents in the lumbosacral spinal cord.

Animals↗

PubMed1998

[Characteristics of the innervation of the head and neck].

Innervation of the head and neck differs from other regions of the body in certain respects. In particular, besides the external cuneate nucleus, thick-calibre neck muscle afferents project directly, to the vestibular nuclear complex. This projection is most prominent in segments C2 and 3 and is sparse or absent in more caudal segments. Thus, proprioceptive neck muscle afferents gain direct access to vestibulospinal, vestibulooculomotor and other secondary or even higher order vestibular neurons that receive labyrinthine input. Proprioceptive input via indirect spinovestibular pathways is also most prominent from C2 and 3 compared to more caudal levels. Likewise, thin calibre, mainly nociceptive afferents from cervical segments are channelled via the parabrachial nuclei in the rostral pons to limbic structures different from the targets of thoracolumbar afferents. It is tempting to consider these neuroantomical peculiarities relevant for the pathogenesis of the puzzling symptoms after whiplash injury.

Brain Stem↗

PubMed1998

Muscle fiber type compartmentalization and expression of an immature myosin isoform in the sternocleidomastoid muscle of rabbits and primates.

The sternocleidomastoid muscle is located in the neck and is both a neck rotator and flexor. Cervical dystonia, a focal dystonia disorder, is characterized by forceful involuntary contraction of a group of neck muscles, usually including the sternocleidomastoid. Little is known about the fiber type composition, fiber type compartmentalization and innervation patterns in this muscle in rabbit and primates. Sternocleidomastoid muscles from rabbit and monkey were analyzed for muscle fiber type composition and number, muscle fiber cross-sectional area and patterns of innervation. The sternocleidomastoid muscle was composed of two distinct regions, or compartments, with different fiber type compositions: an outer or superficial region composed of mostly type 2 myofibers and an inner deep region composed of both type 2 and type 1 myofibers. Neonatal myosin heavy chain isoform was detected in approximately 25% of the myofibers in both regions of the muscle. Neuromuscular junctions were located in seven endplate bands approximately 1-3 cm apart throughout the length of the muscle. There is clear evidence of anatomical subdivisions within this muscle. Not only is there variation in fiber type composition between superficial and deep regions of the muscle, but unlike most other mature skeletal muscles, it continues to express neonatal myosin heavy chain isoform in the adult. The motor program for neck movements is extremely complex, and the histological complexity plays a role in allowing for a continuum of movements of the head and neck, from maintenance of posture to rapid head movements.

Adenosine Triphosphatases↗

PubMed2005

[Surgery for the thymoma combined with pure red cell aplasia and myasthenia gravis].

UNLABELLED: Pure red cell aplasia (PRCA) and myasthenia gravis (MG) are respectively combined with thymoma, however, these 3 complications are extremely rare coexisted as a clinical triad. A 73-year-old female with mediastinal tumor found in 2000 was pointed out anemia in June 2002. As PRCA was diagnosed by the bone marrow examination, blood transfusion had been performed. By a chest computed tomography (CT), a thymoma in size of 7 x 5 cm in diameter was recognized in the anterior mediastinum. The serum level of anti-acetylcholine receptor antibody was elevated to be 35 nmol/l. MG was simultaneously diagnosed with a decreased power of neck muscle. The extended thymectomy was performed in August 2002, and pathological diagnosis disclosed a 'type AB' by World Health Organization (WHO) classification. After the operation, the decreased power of neck muscle had been improved, however, PRCA had not been remitted in the early-postoperative term. Blood transfusion had been required (2-4 units/1-2 weeks) for the postoperative 7 months' term. A cyclosporin (250 mg/day) as an adjuvant therapy was administered in April 2003. One month later, the patient's serum level of Hb had been over 10 g/dl without blood transfusion. The patient has been followed up with reducing the dose of cyclosporin. CONCLUSIONS: Surgery for a thymoma combined with PRCA and MG was effective for MG but not for PRCA in an early-postoperative term, however, a multimodality therapy with immunosuppressant as a postoperative adjuvant should bring a favorable outcome to patient's clinical data, and the postoperative long-observation must be critical in this case.

Aged↗