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At least 145 records · Page 8Linked to original sources
PubMed2005

Use of the head shake-sensory organization test as an outcome measure in the rehabilitation of an individual with head movement provoked symptoms of imbalance.

BACKGROUND AND PURPOSE: The purpose of this case report is to highlight the Head Shake (HS) Sensory Organization Test (SOT) (HS-SOT) as an outcome measure in the rehabilitation of a patient with head movement provoked symptoms of dysequilibrium. Despite complaints of imbalance and head movement provoked symptoms, there are individuals who are able to score within normal limits on measures such as the SOT and Berg Functional Balance Test. The HS modification to the SOT can objectively identify abnormal vestibular inputs associated with head motion and maintaining balance. METHODS: This case report describes the examination, intervention, and outcomes for a 71-year old female with a history of imbalance and decreased ambulatory endurance. During examination, the patient presented with SOT scores within functional limits. The HS-SOT was then implemented to assess vestibular function during head motion in standing, with eyes closed. The intervention included balance retraining, dynamic gait activities, lower extremity strengthening, and instruction in a home exercise program. RESULTS: Improvements were noted for all measures. Initially, during the HS-SOT, the patient fell during all 6 trials of the HS modification to condition 5 and her equilibrium score was 12.Posttreatment, she was able to maintain her balance in 5 out of 6 trials and her score increased to 55. The patient reported increased ambulatory endurance and independence with functional activities (ie, walking and turning her head, and stair negotiation without use of a railing). CONCLUSIONS: The HS-SOT quantified the complaint of head movement provoked symptoms for this individual with dysequilibrium and was useful in measuring success of an intervention.

Aged↗
PubMed1991

Bypassing the Saccadic Pulse Generator: Possible Control of Head Movement Trajectory by Rat Superior Colliculus.

Saccades produced by electrical stimulation of the superior colliculus in primates are influenced primarily by the location of the stimulating electrode, with the suprathreshold intensity or frequency of the stimulating pulse train having little effect. Any given collicular site produces a characteristic movement of relatively fixed amplitude and velocity. In accordance with this finding, in models of the saccadic eye movement system the superior colliculus specifies the change of eye position: the velocity of movement components are determined by 'pulse generators' located between the superior colliculus and the oculomotor neurons. Previous findings in rodents, however, have suggested that eye and head movements induced by stimulation at some collicular sites may be critically dependent on stimulation parameters, implying that in these animals the superior colliculus has access to a non-saccadic control system. To investigate this possibility, rats with electrodes implanted into the lateral intermediate layers were stimulated with pulse trains of varying frequency and duration, and the resultant head movements analysed from video tape. At seven of the nine sites studied, amplitude of the horizontal component of the head movement was linearly related to stimulating frequency for fixed-duration trains, in some cases over a ten-fold range. Subsequent variation of train duration showed that amplitude was affected not by frequency as such, but by the number of pulses in the train; frequency was related to the mean velocity of the movement. By appropriate setting of these parameters, independent control of head movement amplitude and velocity could be achieved. These results suggest that the rodent superior colliculus may be able to control head movement without recourse to a pulse generator, and thus influence the trajectory of the movement directly. If so, it may prove to be a useful preparation for testing theories of trajectory formation.

Journal Article↗
PubMed1992

Sensitivity coefficients, trajectories and graphs of a human head-movement model.

With time as the criterion to be optimized, the divergences from optimal head movements show systematic differences in their control signal variables with respect to single behaviours. To clarify these relationships, this study applies manipulation and mathematical analysis of the 6th-order nonlinear head movement model, using the three-fold approach of sensitivity analysis. The sensitivity analysis of the improved and refined head movement model explains the different tasks of the control parameters and their relation to the plant. It shows that width more than height of the agonistic and antagonistic pulses dominate the important behaviours of the movement: acceleration, magnitude and duration.

Head↗
PubMed2006

Discrimination between active and passive head movements by macaque ventral and medial intraparietal cortex neurons.

An important prerequisite for effective motor action is the discrimination between active and passive body movements. Passive movements often require immediate reflexes, whereas active movements may demand suppression of the latter. The vestibular system maintains correct body and head posture in space through reflexes. Since vestibular inputs have been reported to be largely suppressed in the vestibular nuclei during active head movements, we investigated whether head movement-related signals in the primate parietal cortex, a brain region involved in self-motion perception, could support both reflex functions and self-movement behaviour. We employed a paradigm that made available direct comparison of neuronal discharge under active and passive movement conditions. In this study, we demonstrate that a population of intraparietal (VIP (ventral) and MIP (medial)) cortex neurons change their preferred directions during horizontal head rotations depending on whether animals have performed active movements, or if they were moved passively. In other neurons no such change occurred. A combination of these signals would provide differential information about the active or passive nature of an ongoing movement. Moreover, some neurons' responses clearly anticipated the upcoming active head movement, providing a possible basis for vestibular-related reflex suppression. Intraparietal vestibular neurons thus distinguish between active and passive head movements, and their responses differ substantially from those reported in brainstem vestibular neurons, regarding strength, timing, and direction selectivity. We suggest that the contextual firing characteristics of these neurons have far-reaching implications for the suppression of reflex movements during active movement, and for the representation of space during self-movement.

Action Potentials↗
PubMed2002

Brainstem control of head movements during orienting; organization of the premotor circuits.

When an object appears in the visual field, animals orient their head, eyes, and body toward it in a well-coordinated manner (orienting movement). The head movement is a major portion of the orienting movement. Interest in the neural control of head movements in the monkey and human have increased in the 1990's, however, fundamental knowledge about the neural circuits controlling the orienting head movement continues to be based on a large number of experimental studies performed in the cat. Thus, it is crucial now to summarize information that has been clarified in the cat for further advancement in understanding the neural control of head movements in different animal species. The superior colliculus (SC) has been identified as the primary brainstem center controlling the orienting. Its output signal is transmitted to neck motoneurons via two major separate pathways: one through the reticulospinal neurons (RSNs) in the pons and medulla and the other through neurons in Forel's field H (FFH) in the mesodiencephalic junction. The tecto-reticulo-spinal pathway controls orienting chiefly in the horizontal direction, while the tecto-FFH-spinal pathway controls orienting in the vertical direction. In each pathway, a subgroup of neurons functions as premotor neurons for both extraocular and neck motoneurons, while others are specified for each, which allows both coordinated and separate control of eye and head movements. Head movements almost always produce shifts in the center of gravity that might cause postural disturbances. The postural equilibrium may be maintained by transmitting the orienting command to the limb segments via descending axons of the reticulospinal and long propriospinal neurons. The SC and brainstem relay neurons receive descending inputs from higher order structures such as the cerebral cortex, cerebellum, and basal ganglia. These inputs may serve context-dependent control of orienting by modulating the activities of the primary brainstem pathways.

Animals↗
PubMed1994

Eye and head movements in patients with achromatopsia.

The diagnosis of patients with rod monochromatism (RM) and blue-cone monochromatism (BCM) may be difficult. The relative direction and symmetry of nystagmus of the two eyes, as well as the existence or nature of rhythmic head movements, are not known. We analyzed simultaneous eye and head movement recordings of 16 patients with RM and three patients with BCM. Longitudinal examinations were performed in seven patients. Younger patients had pendular, intermittent or continuous oblique nystagmus with both eyes oscillating in phase or out of phase with equal amplitudes. Older patients had continuous symmetrical oblique jerk nystagmus with decreasing velocities in the slow phase. In two children, we demonstrated evolution from pendular to predominantly jerk nystagmus. Rhythmic head movements were detected in all children. Patients with RM and BCM exhibit a distinct entity of nystagmus and can be differentiated from patients with congenital or latent nystagmus. However, eye and head movements can mimic spasmus nutans.

Adolescent↗
PubMed1997

Modeling study of compensatory head movements in lame horses.

OBJECTIVE: To study the role of head movements in lame horses. SAMPLE POPULATION: 11 Dutch Warmblood horses. PROCEDURE: A 2-segment 2-dimensional inverse dynamic model of trotting horses was developed: trunk and head/neck segment joined in a neck joint. Model input consisted of averaged segmental inertial properties and averaged kinematic data, taken from 11 horses, trotting on a treadmill (3.5 m/s) in 3 conditions of induced lameness: sound, mildly lame, and moderately lame. Dynamic and static effects were analyzed. RESULTS: Dynamic effects were found to be considerably larger than static effects. In the moderately lame condition, the maximal neck joint vertical force during the lame stance phase had a 27% decrease, compared with the sound situation. Neck joint sagittal torque and maximal vertical force on the trunk decreased by 31 and 13%, respectively. Load distribution between forelimb and hind limb indicated a relative load shift from the lame forelimb to the diagonal hind limb during the lame stance phase. The sound contralateral forelimb carried a higher load while the ipsilateral hind limb was unloaded. CONCLUSION: It could be concluded that asymmetric head movements have a major role in lameness compensation, which can be explained by inertial interaction between trunk and head/neck segment. Static effects, such as caudad shifting of the body center of mass, are of minor importance. CLINICAL RELEVANCE: This report clarifies the mechanism of lameness compensation and the method of lameness diagnosis.

Animals↗
PubMed2004

Visual prosody and speech intelligibility: head movement improves auditory speech perception.

People naturally move their heads when they speak, and our study shows that this rhythmic head motion conveys linguistic information. Three-dimensional head and face motion and the acoustics of a talker producing Japanese sentences were recorded and analyzed. The head movement correlated strongly with the pitch (fundamental frequency) and amplitude of the talker's voice. In a perception study, Japanese subjects viewed realistic talking-head animations based on these movement recordings in a speech-in-noise task. The animations allowed the head motion to be manipulated without changing other characteristics of the visual or acoustic speech. Subjects correctly identified more syllables when natural head motion was present in the animation than when it was eliminated or distorted. These results suggest that nonverbal gestures such as head movements play a more direct role in the perception of speech than previously known.

Adult↗
PubMed1998

Head movement in normal subjects during simulated brain imaging.

OBJECTIVE: Videotape images of 30 volunteers were used to classify and measure head movements that may occur during brain imaging. METHODS: A simple videotape setup was designed to record simultaneously the lateral and vertex views of the subject's head. Volunteer subjects were positioned for brain imaging and their heads were videotaped for 2 hr. Head movement was identified and measured. RESULTS: All subjects demonstrated angular movement within the transaxial plane (rotation of the head). There was angular movement in the sagittal plane and translation of the transaxial plane. There was no movement of the coronal plane, nor was there any translational movement of the sagittal plane. CONCLUSION: The most dominant head movement was rotation. The effects of other factors such as height, weight, age, smoking habits, and caffeine and alcohol intake could not be determined with this sample size.

Adolescent↗
PubMed1979

Reflex connexions of motoneurones of muscles involved in head movement in the cat.

1. The reflex connexions from muscle afferents and ventral root fibres to the motoneurones of the muscles biventer-cervicis, complexus, sternocleidomastoid, trapezius and splenius, the principal muscles involved in head movement in the cat, were studied with the technique of intracellular recording. 2. Electrical stimulation of homonymous muscle afferents of biventer-cervicis and complexus, sternocleidomastoid and trapezius, at strengths below 1.6 times threshold of the dorsal root afferent volley, produced monosynaptic e.p.s.p.s in the corresponding motoneurones. Recruitment of higher threshold muscle afferents produced additional p.s.p.s with longer central delays. 3. Stimulation of low-threshold muscle afferents did not produce any p.s.p.s in the motoneurones of the ipsilateral antagonist. Stimulation of higher threshold afferents evoked i.p.s.p.s with central delays longer than 1.6 msec, or mixed e.p.s.p.-i.p.s.p.s in the ipsilateral antagonist. 4. Mixed e.p.s.p.-i.p.s.p.s or i.p.s.p.s with central delays longer than 1.5 msec were evoked in trapezius motoneurones upon stimulation of high threshold afferents from biventer-cervicis and complexus, while stimulation of low-threshold biventercervicis and complexus afferents evoked no p.s.p.s in trapezius motoneurones. 5. Stimulation of contralateral low-threshold biventer-cervicis and complexus afferents evoked a sequence of i.p.s.p. disinhibition in sternocleidomastoid motoneurones, and vice versa, with central delays longer than 1.7 msec. 6. Stimulation of the deafferented biventer-cervicis, complexus, splenius, sternocleidomastoid and trapezius muscle nerves frequently activated interneurones in the ventral horn at monosynaptic central delays. Activation of homoynmous ventral root fibres rarely evoked p.s.p.s in biventer-cervicis, complexius, splenius or sternocleidomastoid motoneurones, while it produced disynaptic i.p.s.p.s in 80% of trapezius motoneurones. 7. It is concluded that Ia reciprocal inhibition and recurrent inhibition, two reflex circuits which are so prominent in limb segments of the spinal cord, do not play a major role in the generation of head movement. Rather, head movement may be primarily controlled from supraspinal centres.

Animals↗
PubMed2001

Vestibulospinal control of reflex and voluntary head movement.

Secondary canal-related vestibulospinal neurons respond to an externally applied movement of the head in the form of a firing rate modulation that encodes the angular velocity of the movement, and reflects in large part the input "head velocity in space" signal carried by the semicircular canal afferents. In addition to the head velocity signal, the vestibulospinal neurons can carry a more processed signal that includes eye position or eye velocity, or both (see Boyle on ref. list). To understand the control signals used by the central vestibular pathways in the generation of reflex head stabilization, such as the vestibulocollic reflex (VCR), and the maintenance of head posture, it is essential to record directly from identified vestibulospinal neurons projecting to the cervical spinal segments in the alert animal. The present report discusses two key features of the primate vestibulospinal system. First, the termination morphology of vestibulospinal axons in the cervical segments of the spinal cord is described to lay the structural basis of vestibulospinal control of head/neck posture and movement. And second, the head movement signal content carried by the same class of secondary vestibulospinal neurons during the actual execution of the VCR and during self-generated, or active, rapid head movements is presented.

Animals↗
PubMed1998

Changes in heart rate and respiration rate in patients with vestibular dysfunction following head movements which provoke dizziness.

Patients with vestibular dysfunction often complain of additional symptoms typical of panic disorder and/or hyperventilation. This study investigated whether autonomic and respiratory symptoms reported by patients with vestibular disorders were associated with objective changes in heart and respiration rate following head movements provoking dizziness. Subjective ratings of symptoms and anxiety and objective measures of heart and respiration rate were obtained from 29 patients and 16 healthy controls immediately before and after the subjects performed three standardised sets of vigorous head movements. Within-group analyses revealed greater increases in respiration rate following head movement among patients who complained of more somatic symptoms, both during the previous 2 months and following head movement.

Adult↗
PubMed1988

Contralateral head movements produced by microinjection of glutamate into superior colliculus of rats: evidence for mediation by multiple output pathways.

One of the major efferent pathways of the superior colliculus crosses midline to run caudally in the contralateral predorsal bundle, innervating targets in the brain stem and eventually reaching the cervical spinal cord. A variety of evidence suggests that this tecto-reticulo-spinal pathway may mediate the orienting movements that can be evoked by tectal stimulation. However, we have recently found that orienting head movements can still be obtained in rats after section of the tecto-reticulo-spinal pathway, implying that additional pathways are also involved. The present study sought to test this implication, by taking advantage of the fact that in rats the cells of origin of the tecto-reticulo-spinal pathway are largely segregated within the lateral part of the stratum album intermediate. It is thus possible to find out whether orienting head movements can be produced by a cell-excitant from tectal regions that contain few cells of origin of the tecto-reticulo-spinal pathway. Hooded rats in an open field were filmed during microinjections of sodium L-glutamate (50 mM, 200 nl) into the superior colliculus, and the films analysed for the appearance of contralaterally directed movements of the head and body. Subsequent histological reconstruction of the injection sites indicated that such movements could be obtained from widespread areas within the superior colliculus, including not only lateral stratum album intermediale but also the deep layers, and parts of the medial superficial and intermediate layers. Moreover, sites in or close to lateral stratum album intermediate often gave circling movements with downward pointing head, whereas some sites outside lateral stratum album intermediale gave sustained immobility with the head pointing contralaterally and upwards. This evidence supports the view that tectal efferent pathways besides the tecto-reticulo-spinal pathway are involved in the control of head movement. In addition, at least some of these pathways are not collaterals of the tecto-reticulo-spinal pathway, since the movements were obtained from collicular regions with few tecto-reticulo-spinal pathway cells. Finally, the results are consistent with the view that different collicular output pathways mediate movements that have different functions.

Animals↗
PubMed1997

Effect of direction of head movement on motion sickness caused by Coriolis stimulation.

BACKGROUND: During constant speed rotation of the body, head rotation about an axis other than the axis of rotation of the body (i.e., Coriolis is stimulation) induces motion sickness. HYPOTHESES: The position of the body relative to the center of rotation will influence the sickness caused by Coriolis stimulation; the direction of head movement will not affect the sickness caused by Coriolis stimulation. METHOD: There were 24 seated subjects (12 male, 12 female) who made 30 degrees pitch motions of the head every 30 s while rotating about a vertical axis at 10 r.p.m. on a turntable at two separate locations: a) at the center of rotation; and b) 0.75 m from the center of rotation. After each head movement the subjects gave ratings of motion illness. RESULTS: There was no significant difference between illness 0.75 m from the center of rotation and illness at the center of rotation, or between the illness ratings from male and female subjects. Moving the head up from the horizontal caused significantly fewer increases in ratings of motion illness than moving the head back down to the horizontal. CONCLUSIONS: Precise location of the body at the center of rotation is not critical during Coriolis stimulation, but the direction of head movement has a large effect on nausea. An influence of somatosensory information on sickness caused by Coriolis stimulation is suggested.

Adult↗