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At least 127 records · Page 7Linked to original sources

PubMed1981

Neck muscle resistance to head impact.

The role of neck muscles in the body's response to the "whiplash" type of motion which occurs during frontal impact has been studied. This type of motion was simulated by a sudden backward pull of a subject's head. Head and neck response to low-level acceleration has been researched by recording the externally applied force, the head accelerations in the median sagittal plane, and the electrical activity in the sternomastoid muscle (EMG) as functions of time. The resultant acceleration-time curve and recorded EMG have been analyzed, with numerical values of applied resistance to the external force recorded. An analog computer model was built incorporating resistance developed by two main variable: 1) the elasticity coefficient; 2) the active damping factor. Together these two variables, combined with a resistance function, enable us to measure the resistance of the head/neck response. Using this model, variations in magnitude of these two components were studied under six varying conditions of impact: 1) length of warning time; 2) type of instruction given to the subject; 3) amount of previous experience on the part of the subject in similar situations; 4) anticipation of impact by the subject; 5) magnitude and kind of impact; 6) presence or absence of a preload.

Acceleration↗

PubMed2006

Effects of neck muscles vibration on the perception of the head and trunk midline position.

The present study focused on the influence of neck vibration on the perception of the head and trunk midline position (orientation and localization). The orientation of the head and trunk was investigated by the rolling adjustment of a rod on their midline while their localization was investigated by the adjustment of the position of a visual dot as being straight-ahead the eyes or the sternum. The first experiment investigated whether a head-trunk dissociation was induced by the unilateral vibration of neck muscles in upright and restrained subjects. Results showed that the subjective orientation and localization of whole-body midline were shifted toward the vibrated side. The second experiment determined the effect of the neck muscles vibration when the subjects were lying on their side. The effect of vibration disappeared when the side of vibration was opposed to the side of postural inclination and it was stronger than in the upright position when the side of vibration and the side of postural inclination were congruent. Whereas, results suggested that the input from neck muscle proprioceptors participates directly to the elaboration of the egocentric space, the question may be raised as to how the sensory cues interacted in their contribution to the neural generation of an egocentric, body centred coordinate system.

Adult↗

PubMed1995

Effects of inflammatory irritant application to the rat temporomandibular joint on jaw and neck muscle activity.

An electromyographic (EMG) study was carried out in 40 anaesthetized rats to determine if the activity of jaw and neck muscles could be influenced by injection of the small-fibre excitant and inflammatory irritant mustard oil into the region of the temporomandibular joint (TMJ). Injection of a vehicle (mineral oil, 20 microliters) did not produce any significant change in EMG activity. In contrast, injection of mustard oil (20 microliters, 20%) evoked increases in EMG activity in the jaw muscles but not in the neck muscles. The increased EMG activity evoked by mustard oil was reflected in 1 or 2 phases of increased activity. The early EMG increase occurred soon after the mustard oil injection (mean latency +/- SD: 3.5 +/- 2.3 sec), peaked within 1 min, and then subsided (mean duration: 7.5 +/- 5.2 min). The later EMG increase occurred at 14.6 +/- 10.0 min after the mustard oil injection and lasted 14.3 +/- 12.3 min. These excitatory effects of mustard oil on the EMG activity of jaw muscles appear to have a reflex basis since they could be abolished by pre-administration of local anaesthetic into the TMJ region. These results document that TMJ injection of mustard oil results in a sustained and reversible activation of jaw muscles that may be related to the reported clinical occurrence of increased muscle activity associated with trauma to the TMJ.

Animals↗

PubMed1986

Neck muscle afferent projections to the brainstem of the monkey: implications for the neural control of gaze.

Brainstem projections of first-order afferent neurons that innervate the suboccipital muscles of the monkey have been determined by using the technique of transganglionic transport of wheat-germ-agglutinin-conjugated horseradish peroxidase (WGA/HRP) and HRP. Neck muscle afferents distribute to several distinct regions located within the caudal brainstem and rostral spinal cord. Terminal labeling was heaviest within the ventral portion of the ipsilateral lateral cuneate nucleus. Muscle afferent terminals also distributed to ventrolateral portions of the pars triangularis division of the cuneate nucleus. Projections were consistent with the known somatotopic (i.e., both place and modality) organization of the cuneate nucleus. Moreover, neck muscle projections to the cuneate nucleus were, in part, coincident with those previously demonstrated for the extraocular muscles (Porter: J. Comp. Neurol. 247:133-143, '86). Sparse terminal projections were noted in the central cervical nucleus. In addition, light terminal labeling was present in group x of the vestibular complex and in an ill-defined region along the lateral margin of the brainstem. Present observations, which provide the first complete description of the central distribution of neck muscle afferent neurons in the primate, may contribute to the known substrate for eye/head coordination.

Animals↗

PubMed1990

Organization of neck muscle motoneurons in the cervical spinal cord of the pigeon.

As a first step towards the analysis of the neural control of pecking behaviour in the pigeon, the cell bodies of neck muscle motoneurons were localized and their somatotopic organization in the cervical spinal cord examined. Fluorescent tracers were injected into single neck muscles and labelled motoneuron cell bodies identified. Labelled perikarya were arranged in longitudinal columns within layers VIII and IX of the ventral horn ipsilateral to the injection site. Cell bodies of neurons innervating different muscles formed distinct columns that extended mainly rostrally from the injection level. Labelling of adjoining portions of one muscle revealed one continuous column of cell bodies. Relative to the neck muscles, the motoneuron perikarya were arranged in a mediolaterally inversed pattern.

Amidines↗

PubMed2005

The activity patterns of neck muscles in professional classical singing.

The study aimed to characterize the activity patterns of neck muscles during classical singing. Muscle usage during inhalation and phonation and the relationship to changes in pitch and vocal loudness was of particular interest. Five professional opera singers (2 males, 3 females) participated. Surface electromyographic activity (EMG) was recorded from the upper trapezius (TR), the sternocleidomastoideus (STM), and the scalenus (SC) muscles and the muscles in the posterior neck region (PN). EMG activity in TR and STM was lowered by EMG biofeedback (BF), and the possible effect of lowered EMG activity in these muscles on the EMG activity of SC and PN was analyzed. A strain gauge sensor recorded the chest circumference of the thorax. Three singing tasks were performed. Each task was performed three times with variation in vocal loudness and pitch. After the first performance of the singing tasks, the BF session was carried out. Thereafter muscle activity was recorded in repeat performances of the same tasks, and the EMG amplitude of all muscles was compared before and after BF. We conclude that STM and SC showed correlated activity patterns during inhalation and phonation by classical singers. Second, substantial muscle activity was observed in PN during inhalation and phonation. BF performed on TR and STM had a secondary effect of lowering EMG activity in SC and PN. The activity of all neck muscles was markedly elevated when singing in the highest pitch. There was no consistent task-based difference in EMG amplitude for the other singing tasks.

Adult↗

PubMed1980

[Projection of neck muscle afferents to the brain stem of the cats (author's transl)].

In order to investigate the afferent projection of neck muscles biventer cervicis, splenius and occipitoscapularis, extremities were performed on cats anaesthetized with chloralose urethane. 246 neurons were found to respond to electrical stimulation of these muscle nerves and they were located mainly in the ipsilateral external cuneate nucleus (242; 98.3%) and the remaining 4 neurons were in the rostral tip of the main cuneate nucleus. It was found that 241 neurons responded to only one of these afferent nerves, 3 neurons received convergent inputs from biventer cervicis and occipitoscapularis nerve and one neuron from biventer cervicis and great auricural nerve. Out of 241 neurons studied, 97 neurons (40.3%) responded to biventer cervicis, 88 (36.5%) to splenius and 56 (23.2%) to occipitoscapularis. 40 out of the 97 biventer cervicis responded neurons showed the monosynaptic firing. 51 out of the biventer cervicis responded neurons, 35 out of the splenius and 34 out of the occipitoscapularis responded neurons fired the first spike response at stimulus strength below 1.7 times the threshold of the largest afferents of each nerves suggesting group I afferents are responsible for the discharges. The monosynaptically activated neurons showed somatotopic distribution in the nucleus; biventer cervicis responded neurons locate in the most lateral part, splenius locate in the middle and occipitoscapularis locate in the medial part of the external cuneate nucleus. Antidromic discharges were evoked in 43/143 (30.1%) of the external cuneate neurons by electrical stimulation of the ipsilateral inferior peduncle and anterior lobes IV and V of the cerebellum. No such and antidromic discharges could be evoked by electrical stimulation of the contralateral thalamus. It was concluded that the relay neurons of the external cuneate nucleus from biventer cervicis, splenius and occipitoscapularis neck muscles projected their axons to the ipsilateral cerebellum but not to ventral posterolateral (VPL) and ventral posteromedial (VPM) nucleus of the contralateral thalamus.

Action Potentials↗

PubMed2004

Functional synergies among neck muscles revealed by branching patterns of single long descending motor-tract axons.

In this chapter, we describe our recent work on the divergent properties of single, long descending motor-tract neurons in the spinal cord, using the method of intra-axonal staining with horseradish peroxidase, and serial-section, three-dimensional reconstruction of their axonal trajectories. This work provides evidence that single motor-tract neurons are implicated in the neural implementation of functional synergies for head movements. Our results further show that single medial vestibulospinal tract (MVST) neurons innervate a functional set of multiple neck muscles, and thereby implement a canal-dependent, head-movement synergy. Additionally, both single MVST and reticulospinal axons may have similar innervation patterns for neck muscles, and thereby control the same functional sets of neck muscles. In order to stabilize redundant control systems in which many muscles generate force across several joints, the CNS routinely uses a combination of a control hierarchy and sensory feedback. In addition, in the head-movement system, the elaboration of functional synergies among neck muscles is another strategy, because it helps to decrease the degrees of freedom in this particularly complicated control system.

Animals↗

PubMed1994

Electromyographic analysis of neck muscle fatigue in patients with osteoarthritis of the cervical spine.

Median frequency parameters of myoelectric signals were studied in 25 patients with osteoarthritis of the cervical spine and in 25 normal subjects. The median frequency parameters included initial median frequency and slope of the median frequency during 20%, 50%, 80%, and 100% of maximum voluntary contractions (MVC). The subjects performed sustained, isometric constant-force contractions of forward and backward bend of the cervical spine. The median frequency signals were obtained from the anterior (sternocleidomastoid) and posterior (upper trapezius) neck muscles. The results showed that at moderate and high forces (i.e., 50%, 80%, and 100% MVC) the anterior neck muscles in patients with osteoarthritis of the cervical spine fatigued faster than those of normal subjects. The posterior neck muscles in patients fatigued faster compared to normal subjects at high force levels (i.e., 80% and 100% MVC). This indicates a higher fatigue of the anterior and posterior neck muscles associated with arthritic changes of the cervical spine. Rehabilitation programs must consider these muscular changes to obtain optimal outcomes.

Adult↗

PubMed2001

Neck muscles in the rhesus monkey. I. Muscle morphometry and histochemistry.

Morphometric methods were used to describe the musculotendinous lengths, fascicle lengths, pennation angles, and cross-sectional areas of neck muscles in adult Macaca mulatta monkeys. Additionally, muscles were frozen, sectioned, and stained for ATPase activity to determine fiber-type composition. Individual rhesus muscles were found to vary widely in their degree of similarity to feline and human muscles studied previously. Suboccipital muscles and muscles supplied by the spinal accessory nerve were most similar to human homologs, whereas most other muscles exhibited architectural specializations. Many neck muscles were architecturally complex, with multiple attachments and internal aponeuroses or tendinous inscriptions that affected the determination of their cross-sectional areas. All muscles were composed of a mixture of type I, IIa, and IIb fiber types the relative proportions of which varied. Typically, head-turning muscles had lower proportions of type II (fast) fibers than homologous feline muscles, whereas extensor muscles contained higher proportions of type II fibers. The physical and histochemical specializations described here are known to have a direct bearing on functional properties, such as force-developing capacity and fatigue-resistance. These specializations must be recognized if muscles are to be modeled accurately or studied electrophysiologically.

Adenosine Triphosphatases↗

PubMed1988

Eye-head coupling in humans. I. Simultaneous recording of isolated motor units in dorsal neck muscles and horizontal eye movements.

A tonic coupling between the horizontal component of eye position and dorsal neck muscle activity has been demonstrated in the cat and monkey. In order to demonstrate this synergy in humans and study its characteristics, we have measured the relation between the firing rate of individual motor unit of the splenius muscle and voluntary horizontal shifts of gaze using 5 degrees steps, in head-fixed subjects. Eye movement recording was achieved by conventional binocular electro-oculography and the activity of the right splenius muscle was recorded with Bronks coaxial bipolar electrodes inserted manually at the C4-C5 intervertebral level. The activity of 51 motor units in 10 subjects has been recorded. For all subjects, motor units firing rate increased when the gaze shifted to the ipsilateral side, and both increase in firing rate and recruitment were observed. These results demonstrate that the tonic eye head synergy is also present in man.

Action Potentials↗

PubMed2001

Intramuscular hemangioma of posterior neck muscles.

Intramuscular hemangiomas of the head and neck are rare tumors, sparsely reported. They usually present themselves as a mass which enlarges suddenly. A case of intramuscular hemangioma involving the posterior neck muscles is presented. Computed tomography scanning, magnetic resonance imaging and angiography revealed the vascular nature of this lesion. Surgery consisted of a wide excision. The patient is free of disease after a 4-year follow-up.

Adult↗

PubMed2001

Neck muscle responses to abrupt vertical acceleration in the seated human.

The control of neck muscle during marked changes in "g" loading must be to protect head-trunk orientation. However, little is known about the organization of reflexes. We therefore investigated the shortest latency in neck muscle evoked by abrupt ascending and descending vertical acceleration with a stroke of 20 cm and peak acceleration 0.4xg in six healthy subjects. The subjects were seated upright and restrained on a chair driven by a hydraulic servo system. Ascent induced small responses in sternocleidomastoid muscles (SCMs) with a latency of 24.0 ms (SE 1.7) from onset of head acceleration, followed by larger responses of 100 ms in duration. In comparison the responses in SCMs evoked by descent were significantly delayed, with greater interindividual variations at 44.1 ms (SE 3.1) and smaller in amplitude than responses in ascent. Latencies were consistent and showed no habituation. In order to eliminate stretch components, we measured the neck responses to vertical acceleration with the head fixed by cervical collar. The latency of the fast response of SCM evoked by ascent was not significantly different from the latency of SCMs without the collar. These results may indicate that the fast responses of SCMs to sudden ascent may be composed of a vestibular-collic reflex for making the neck and head rigid for defense to sudden gravitational change.

Acceleration↗

PubMed2002

Evaluation of cervical range of motion and isometric neck muscle strength: reliability and validity.

OBJECTIVE: To examine the test-retest reliability and construct validity of cervical active range of motion and isometric neck muscle strength as measured by the Multi Cervical Rehabilitation Unit (Hanoun Medical Inc., Ontario). DESIGN: A cross-sectional study. SETTING: Institutional practice. SUBJECTS: Twenty-one patients with neck pain and 25 healthy volunteers. METHODS: After a trial-run session, active range of motion (AROM) was measured in the subsequent two sessions, with 2-3 days in between. During each session, three measurements were taken for each direction (flexion, extension, lateral flexions and rotations). The measurement of isometric strength was after a 15-minute break following completion of the measurement of AROM. Three measurements were made for each of the six directions (flexion, extension, lateral flexions, protraction and retraction). The software of the Multi Cervical Rehabilitation Unit automatically recorded and calculated the maximum AROM and isometric strength. RESULTS: There was a good to high level of reliability in the measurement of AROM for both groups of subjects, with intraclass correlation coefficients (ICCs) ranging from 0.81 to 0.96. Results also demonstrated very good to excellent reliability in isometric strength measurement (ICCs ranged from 0.92 to 0.99). Moreover, there was a significant difference in isometric neck muscle strength (p = 0.001) and in AROM (p = 0.034) between the two groups. CONCLUSIONS: The Multi Cervical Rehabilitation Unit was found to be reliable and valid for testing the cervical active range of motion and isometric neck muscle strength for both normal and patient subjects.

Adult↗

PubMed1999

Subjective straight-ahead during neck muscle vibration: effects of ageing.

The subjective visual straight-ahead (SVA) was measured psychophysically before and during unilateral vibration of the posterior neck muscles in order to determine the particular contribution of neck muscle spindles to the perception of body orientation during ageing. We found a symmetrical increase of the vibration-induced displacement of the SVA with advancing age (R = +0.73, p < 0.01, n = 60) in 30 healthy subjects of different ages (range 20-81 years). These data indicate the cervical proprioceptive contribution to multisensory body orientation increases with ageing. One possible interpretation is that the sensorial weight of proprioception increases as the peripheral vestibular input decreases with advancing age, thereby substituting for the lack of vestibular function.

Adult↗

PubMed1983

Quantitative electromyography: response of the neck muscles to conventional helmet loading.

Experiments were conducted to quantify the fatigue of neck muscles which occurs during loading of these muscles by: the head itself (CON), the conventional SPH-4 helmet (HEL), and a combination of the SPH-4 helmet with Night Vision Goggles (H/NVG). Two exercise periods of 5 min and 35 min duration, respectively, were performed by the 5 subjects, during which a subject would rotate the head laterally (from side-to-side) in the CON, HEL, or H/NVG configuration. Immediately thereafter, the subject would position his head in an isometric head dynamometer and exert a sustained right lateral (LAT) neck contraction, or forward (FOR) neck contraction at 70% of his maximum strength, during which his endurance time to fatigue was recorded, and the EMG over the right sternocleidomastoid (SCM) muscle, and over the posterior trapezius/splenius muscles was continuously recorded. The root-mean-squared (RMS) amplitude of the electromyogram (EMG) continuously increased during the fatiguing contraction, being 78% greater (on the average) by the time of fatigue, and the center frequency of the EMG power spectrum continuously decreased, being 27% less (on the average) at the fatigue end-point. Some variability with head loading configuration and contraction mode was observed. These results are significant since they demonstrate that the EMG of neck muscles can be used as a noninvasive, objective and quantitative index of the neck muscle fatigue.

Adult↗

PubMed1993

Decrease of contralateral neglect by neck muscle vibration and spatial orientation of trunk midline.

Three patients with a right hemisphere lesion and marked left-sided neglect without visual field defects were asked to detect and identify stimuli which were tachistoscopically presented in the left or right visual half-field. Neglect of stimuli presented in the contralesional left visual field, which was observed when the patient's body was in a normal upright position with trunk, head and gaze oriented straight ahead to the middle of the projection screen, could be reduced by vibrating the left posterior neck muscles as well as by turning the trunk 15 degrees to the left. In contrast, unspecific stimulation on the left side of the patient's body, produced by vibrating the left hand muscles or the proprioceptive signal induced by turning the head 15 degrees to the left, had no compensatory effects. The results showed that the afferent information about real lengthening of the left posterior neck muscles (produced by turning the trunk) as apparent lengthening of these muscles (produced by their vibration), leads to a remission of contralateral neglect. Thus, the proprioceptive input from the neck muscles, i.e. the head-on-trunk signal, appears to influence the extension of the neglected part of space in patients with neglect. The signal seems to contribute substantially to the neural generation of the egocentric frame of reference that allows the determination of body position with respect to visual space. We hypothesize that the reduction of neglect by vibration of the contralateral posterior neck muscles is based on a shift of the subjective spatial localization of the sagittal midplane in the contralesional direction and a corresponding alteration of the egocentric coordinate system necessary for visuomotor coordination and exploration of space.

Aged↗

PubMed1994

Subjective body orientation in neglect and the interactive contribution of neck muscle proprioception and vestibular stimulation.

Three patients with a right, predominantly parietal lesion and marked left-sided neglect without visual field defects were asked to direct a laser point to the position which they felt to lie exactly 'straight ahead' of their bodies' orientation. Whereas in both light and darkness, the subjective body orientation was close to the objective body position in the control groups, the three neglect patients localized the body's sagittal midplane approximately 15 degrees to the right of the objective orientation. No relevant differences of 'straight ahead' were found between the neglect patients and controls in the vertical plane. The neglect patients' horizontal displacement of sagittal midplane to the right could be compensated for either by neck muscle vibration or by caloric vestibular stimulation on the left side. When vestibular stimulation was combined with neck muscle vibration, the horizontal deviation linearly combined by adding or neutralizing the effects observed when both types of stimulation were applied exclusively in the control groups as well as in the neglect patients. Moreover, data analysis revealed that the neglect patients' ipsilesionally displaced subjective body orientation does not result from a disturbed primary perception or disturbed transmission of the vestibular or proprioceptive input from the periphery. The present results support the hypothesis that the essential aspect leading to neglect in brain-damaged patients is a disturbance of those cortical structures that are crucial for transforming the sensory input coordinates from the peripheral sensory organs--here the retina, neck muscle spindles and cupulae--into an egocentric, body-centred coordinate frame of reference. In neglect patients the coordinate transformation seems to work with a systematic error and deviation of the spatial reference frame to the ipsilesional side leading to a corresponding displacement of subjective localization of body orientation. It can be concluded further that neck muscle proprioception and vestibular stimulation directly interact in contributing to the subject's mental representation of space. The data suggest that the afferent information from these different input channels is used simultaneously for computing egocentric, body-centred coordinates that allow us to determine our body position in space.

Adult↗