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PubMed2002

Studies of the role of the paramedian pontine reticular formation in the control of head-restrained and head-unrestrained gaze shifts.

Results of three experiments related to the role of the paramedian pontine reticular formation (PPRF) in the control of gaze are described. (1) Chronic unit recording methods, used to study the on-directions of short-lead burst neurons in head-restrained monkeys, and (2) reversible inactivation techniques confirmed the traditional view of the importance of PPRF in the control of horizontal eye movements. Reversible inactivation of neurons in the vicinity of identified short-lead burst neurons produced dramatic reductions in the speed of saccades to horizontal target displacements. The reductions in velocity were largely compensated for by an increase in saccade duration. Only minor, if any, effects were observed upon the velocity, duration, and amplitude of saccades to upward target displacements. (3) Microstimulation was applied to omnipause neurons to gate activity of excitatory burst neurons that discharge during coordinated eye-head movements. The microstimulation failed to noticeably slow (prevent) head movements when stimulation was applied during (prior to onset of) gaze shifts, suggesting that signals relayed to motoneurons innervating the neck muscles are not inhibited by the omnipause neurons. In other words, the desired gaze signal is parsed into eye and head pathways upstream of the excitatory burst neurons.

Animals↗
PubMed1984

Ingestion in fetal sheep and its relation to sleep states and breathing movements.

Swallowing was recorded electromyographically in unanaesthetized fetal sheep in utero during the last third of gestation. In control fetuses bouts of swallowing were, on average, 2.0 min in duration and occurred at intervals of 2.31 h. Swallowing bouts were associated with a low-voltage electrocorticogram, eye movements and, in 82% of instances, with phasic activity in the dorsal neck muscles. These data indicate that fetuses are not in quiet (non-rapid eye movement; n.r.e.m.) sleep when swallowing and also suggest that they are not in r.e.m. sleep as conventionally defined; we consider that fetuses may be in a state of heightened activity resembling wakefulness. Swallowing bouts were always accompanied by fetal breathing movements. When a swallow coincided with an inspiratory effort the diaphragm was briefly inhibited. Evidence was obtained that bouts of fetal ingestive activity were not dependent upon outpourings of fluid from the lungs and were not significantly influenced by volume information from the gastric compartments.

Animals↗
PubMed1989

Vagal gastric efferent activity and its reflex changes in conscious sheep.

Electromyographical recordings from neck muscles reinnervated by the vagus nerve allowed monitoring of vagal output to the reticulo-rumen in conscious sheep. The vagus nerve was sectioned below the nodose ganglion and its central end anastomosed with the peripheral end of the spinal accessory nerve, which innervates the trapezius and mastoido-humeral muscles. Fifty-three vagal efferent units recorded were identified and classified into seven distinguishable types on the basis of their temporal relationship with gastric movements. With respect to their patterns of discharge during the primary cycles type I to type V units were similar to units of the corresponding types described by Iggo & Leek (1967a) in anaesthetized sheep. Evidence for the hypothesis that each type of gastric unit innervates a distinct region of the reticulo-rumen is strongest for types I and IV. Type I units which exhibited a bimodal pattern of discharge closely associated with reticular motility, are presumed to innervate the reticulum. Some of them, so-called Ib because of their second burst with a long tail and their activity during the secondary cycles, are considered to activate the zone of attachment of the reticulum to the rumen. Type IV units which were active during the ruminal contractions of both primary and secondary cycles are considered to innervate the dorsal rumen. Discharges in these gastric units were observed when gastric motility was partially or totally abolished after administering autonomic blocking drugs for each unit tested (n = 25). They consisted of (i) a shortening of intervals between the onset of two successive bursts, and (ii) an increase in the duration of discharge and the number of potentials in the efferent units. As the abolition of gastric motility led to a decrease of gastric afferent input, these results suggest that the gastric centres are under a permanent inhibitory influence from the afferent drive.

Action Potentials↗
PubMed1988

Somatosensory projections to the superior colliculus of the anaesthetized cat.

1. Experiments in anaesthetized cats have shown that the superior colliculus receives deep afferent input from the forelimb and hindlimb, but not from the large superficial neck muscles. 2. Neuronal activity in the superior colliculus is readily elicited by electrical stimulation of C2 and C3 cutaneous nerves. A significant proportion of neurones so activated have multiple receptive fields and some with no identifiable receptive fields in regions innervated by C2 and C3 nerves have receptive fields elsewhere on the body surface. Many collicular neurones activated by C2 and C3 stimulation had no identifiable receptive fields. 3. Natural stimuli to the limbs, hitherto believed to activate only cutaneous receptors, are sufficient to activate deep receptors which contribute to the neuronal responses in the superior colliculus elicited by the natural stimulus. These same natural stimuli set up transmitted vibration adequate to excite receptors some distance from the applied stimulus. 4. No evidence was found for a rigorous somatotopy in the superior colliculus. The great majority of neurones received trigeminal input which is widely distributed throughout the superior colliculus. 5. Tactile stimuli to the face are most effective in eliciting unit activity in the superior colliculus and many neurones activated by these stimuli were shown to be tectospinal neurones. In particular, the specialized receptors of the face, including the glabrous skin of the snout (the planum nasale) and the vibrissae, are major sources of input to collicular neurones including tectospinal neurones. 6. It is suggested that a major role of the superior colliculus is in the organization of head movements associated with the use of the specialized receptor organs of the face in exploratory behaviours. The superior colliculus may also be involved in the organization of aversion movements of the head.

Action Potentials↗
PubMed1989

Head-free pursuit in the human of a visual target moving in a pseudo-random manner.

1. Head and eye movements have been recorded in man during head-free pursuit of a target moving in a pseudo-random manner in the horizontal plane with a motion stimulus composed of the sum of four sinusoids. 2. In an initial experiment the three lowest frequencies remained constant at 0.11, 0.24 and 0.37 Hz, whilst the highest frequency (F4) took values of 0.39, 0.78, 1.56 and 2.08 Hz. Peak velocity of each component was 10 deg/s. When F4 was 0.39 Hz gaze displacement (i.e. the sum of head and eye displacement) was relatively smooth and had a mean velocity gain of 0.95. As F4 was increased gaze displacement contained more saccadic activity and gaze velocity gain for the three lower-frequency components was significantly (P less than 0.001) reduced to a minimum level of 0.66 when F4 was 1.56 Hz. 3. A similar reduction in gain of the lower-frequency components was obtained when the velocity of F4 was increased as a ratio of the velocity of the lower frequencies from 0 to 4. 4. When the frequency composition of the stimulus was varied so that the two highest frequencies were closely spaced, gaze velocity gain for the highest frequency was always significantly higher than that of the next lower frequency, indicating a true enhancement of the highest-frequency component. 5. Changing the lowest-frequency component of the stimulus resulted in a significant shift in the gaze velocity phase profile as a function of frequency, so that phase advance was always associated with the lowest frequency even when this was as high as 0.89 Hz. 6. These changes in gain and phase of gaze velocity with the frequency content of the stimulus were similar to those previously described for head-fixed pursuit and visual suppression of the vestibulo-ocular reflex (VOR) and implicate the frequency-dependent, non-linear visual feed-back mechanisms in gaze control. 7. A number of the non-linear characteristics of gaze velocity were also observed in a somewhat modified form in the head displacement gains and phases, implying that the drive to the neck muscles is also derived from the same non-linear visual feed-back source. 8. The role of the VOR in head-free pursuit was tested by exposing the subject to whole-body motion on a turntable which countered the volitional head movement generated by the subject.(ABSTRACT TRUNCATED AT 400 WORDS)

Eye Movements↗
PubMed1998

Cervical spine vertebral and facet joint kinematics under whiplash.

Whiplash injuries sustained during a rear-end automobile collision have significant societal impact. The scientific literature on whiplash loading is both diverse and confusing. Definitive studies are lacking to describe the local mechanisms of injury that induce either acute or chronic pain symptoms. A methodology has been presented to quantify the kinematics of the cervical spine components by inducing controlled whiplash-type forces to intact human head-neck complexes. The localized facet joint kinematics and the overall segmental motions of the cervical spine are presented. It is anticipated that the use of this methodology will assist in a better delineation of the localized mechanisms of injury leading to whiplash pain.

Acceleration↗
PubMed1964

DYNAMICS OF MOTION PERCEPTION IN THE DESERT LOCUST.

The torque produced by the neck muscles of a locust mounted coaxially in an illuminated cylindrical striped drum follows small sinusoidal oscillations of the drum. Peak-to-peak oscillations of 0.03 degree (+/- 0.02 degree) at 0.1 cy/sec elicit measurable responses. Several features of this visual response to drum oscillation can be expected theoretically on the basis of a formal neural mechanism similar to that inferred by Hassenstein and Reichardt for constant-velocity motion perception in the bettle eye.

Animals↗
PubMed2005

Effect of intensive acupuncture on pain-related social and psychological variables for women with chronic neck and shoulder pain--an RCT with six month and three year follow up.

OBJECTIVES: This study examines whether intensive acupuncture treatment can improve several social and psychological variables for women with chronic pain in the neck and shoulders, and whether possible effects are long-lasting. The effects on pain have been reported elsewhere. METHODS: Twenty-four female office workers (47 +/- 9 years old, mean +/- SD) who had had neck and shoulder pain for 12 +/- 9 years, were randomly assigned to a test group or a control group. Acupuncture was applied 10 times during three to four weeks either at presumed acupuncture points for pain (test group) or at sham points (control group). In addition, acupressure was given to patients between treatments, at either real or sham points. Questionnaires for social and psychological variables were completed before each treatment, just after the course, and six months and three years later. RESULTS: The pain-related activity impairment at work was significantly less in the test group than the controls by the end of treatment (P < 0.04). Also there were significant differences between the groups for quality of sleep, anxiety, depression and satisfaction with life (P < 0.05). At six months and three years follow ups the acupuncture group showed further improvements in most variables and was again significantly different from the control group. CONCLUSION: Intensive acupuncture treatment may improve activity at work and several relevant social and psychological variables for women with chronic pain in the neck and shoulders. The effect may last for at least three years.

Acupuncture Analgesia↗
PubMed1994

Postmortem angiographic study of degenerative vascular changes in arteries supplying the cervicobrachial region.

OBJECTIVES: To study the prevalence of degenerative changes in the arteries supplying the cervicobrachial region, and their relation to cervical disc degeneration. METHODS: Fifty postmortem aortic arch angiographies were evaluated for occlusions and variations in the diameter of the vertebral arteries and thyro- and costocervical trunks, as well as for tortuosity, average diameter and the highest cervical level to which the ascending cervical artery, an upward continuation of the thyrocervical trunk, and the deep cervical artery, an upward continuation of the costocervical trunk, ascended. RESULTS: Localised segmental narrowings, usually situated close to the ostia of the arteries, were common, whereas total occlusions were rare. Thirty (60%) of the subjects showed a segmental narrowing at least in one of the six arteries analysed, while only two (4%) showed an occluded artery, which in both the cases was the thyrocervical trunk. Narrowings were most common in vertebral arteries, followed by costocervical and thyrocervical trunks. Segmental narrowings, as well as general tortuosity of the arteries, increased with age. It was also found that ascending and deep cervical arteries did not run as high up in the posterior neck muscles in older people as in younger ones. Twenty three subjects with marked cervical disc degeneration showed on average 2.3 arteries with segmental narrowings, while the corresponding figure for twenty seven subjects without disc degeneration was 0.6. Both the segmental narrowings and the disc degeneration, however, were strongly associated with age, and thus the causality between the former two remained unclear. CONCLUSION: The study showed that degenerative changes are common in the arteries supplying the cervicobrachial area, indicating that impaired blood flow might play a part in some cervicobrachial disorders.

Adolescent↗
PubMed2001

Two cases of isolated first rib fracture.

Isolated first rib fractures are uncommon. They are usually associated with severe blunt trauma, although other mechanisms have been suggested, these being (a) indirect trauma, (b) sudden contraction of the neck muscles, and (c) stress or fatigue fractures attributable to repeated pull of muscles. Two cases are reported of stress fracture of the first rib, who presented to the accident and emergency department.

Adolescent↗
PubMed1979

Abnormal head movements.

Abnormal head movements have been studied in a variety of diseases using objective recording techniques and the data analysed with respect to the frequency content of the movement. Flopping, nodding, tic, chorea, myoclonic jerks, and most head tremors involve frequencies of approximately 2 and 4 Hz which correspond to the natural fundamental and second harmonic resonances of the head as determined by the mechanical properties of the head/neck system. These findings provide a basis for classification of abnormal head movements as well as an explanation of the characteristics of those arising from hypotonia of the neck muscles. The similarities between tremor frequencies and natural resonances suggest that in the case of the head, tremor arises from disorders of neural mechanisms normally responsible for the fine control of voluntary head movement and for stabilisation of the head during disturbance of posture. Head movements in cases of congenital nystagmus were found to be of two types. Some were of bizarre waveform, in no way assisted vision, and were taken to be of primarily pathological origin and classified as tremors. Others were learned adaptive responses which assisted vision either by interrupting the nystagmus, as in the case of spasmus nutans, or by compensating for the nystagmus with an inverse waveform and were called nodding. A prerequisite for true compensatory nodding is modified vestibulo-ocular reflex.

Adult↗
PubMed1986

Weakness of head turning in hemiplegia: a quantitative study.

The strength of head turning was measured in normal subjects and in patients with hemiplegia of vascular origin. In normals the strength of head turning to the two sides was not significantly different. In most patients with a cortical, capsular or high brainstem lesion the strength of head turning away from the side of the lesion was reduced. In patients with a medullary lesion the strength of head turning towards the side of the lesion was reduced. The significance of these findings is discussed in relation to the cortical control of the sternocleidomastoid muscle and other muscles involved in the movement of head turning.

Adult↗