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Results for “Postural control”

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PubMed2004

Multiple reference frames for motion in the primate cerebellum.

Knowledge of body motion through space is necessary for spatial orientation, self-motion perception, and postural control. Yet, sensory afferent signals may not directly provide such information to the brain. Because motion detected by the vestibular end organs is encoded in a head-fixed frame of reference, a coordinate transformation is thus required to encode body motion. In this study, we investigated whether cerebellar motion-sensitive neurons encode the translation of the body through space. We systematically changed both the direction of motion relative to the body and the static orientation of the head relative to the trunk. The activities of motion-sensitive neurons in the most medial of the deep cerebellar nuclei, the rostral fastigial nucleus, were compared with those in the brainstem vestibular nuclei. We found a distributed representation of reference frames for motion in the rostral fastigial nucleus, in contrast to cells in the vestibular nuclei, which primarily encoded motion in a head-fixed reference frame. This differential representation of motion-related information implies potential differences in the functional roles of these areas.

Acceleration↗

PubMed2006

Measurement and evaluation of dynamic joint stability of the knee and ankle after injury.

Injuries to the lower extremity, specifically the knee and ankle joints of the human body can occur in any athletic event and are most prevalent in sports requiring cutting and jumping manoeuvres. These joints are forced to rely on the dynamic restraints to maintain joint stability, due to the lack of bony congruence and the inability of the static restraints to handle the forces generated during functional tasks. Numerous variables (proprioception, postural control, electromyography, kinetics/kinematics, dynamic stability protocols) have been measured to better understand how the body maintains joint stability during a wide range of activities from static standing to dynamic cutting or landing from a jump. While the importance of dynamic restraints is not questioned, a recent impetus to conduct more functional or sport-specific testing has emerged and placed a great deal of emphasis on dynamic joint stability and how it is affected by lower extremity injuries. Evidence suggests that surgery and aggressive rehabilitation will not necessarily restore the deficits in dynamic joint stability caused by injury to the anterior cruciate ligament or lateral ankle ligaments. In today's athletic society, there is a major push to return athletes to play as quickly as possible. However, the ramifications of those decisions have not been fully grasped. If an athlete is not fully recovered, a quick return to play could start a vicious cycle of chronic injuries or permanent disability.

Ankle Injuries↗

PubMed2006

Rehabilitation after anterior cruciate ligament reconstruction: criteria-based progression through the return-to-sport phase.

Rehabilitation following anterior cruciate ligament (ACL) reconstruction has undergone a relatively rapid and global evolution over the past 25 years. However, there is an absence of standardized, objective criteria to accurately assess an athlete's ability to progress through the end stages of rehabilitation and safe return to sport. Return-to-sport rehabilitation, progressed by quantitatively measured functional goals, may improve the athlete's integration back into sport participation. The purpose of the following clinical commentary is to introduce an example of a criteria-driven algorithm for progression through return-to-sport rehabilitation following ACL reconstruction. Our criteria-based protocol incorporates a dynamic assessment of baseline limb strength, patient-reported outcomes, functional knee stability, bilateral limb symmetry with functional tasks, postural control, power, endurance, agility, and technique with sport-specific tasks. Although this algorithm has limitations, it serves as a foundation to expand future evidence-based evaluation and to foster critical investigation into the development of objective measures to accurately determine readiness to safely return to sport following injury.

Algorithms↗

PubMedDate not supplied

Labyrinthine and somatosensory convergence upon vestibulospinal neurons.

In awake cats cells forming the lateral (LVST) and medial (MVST) vestibulospinal tracts were identified by employing antidromic stimulation of the spinal cord. Neuronal responses to bilateral vestibular, forelimb, hindlimb, and neck electrical nerve stimulation were analysed. Extracellular recording in the vestibular nuclei was performed via a glass micropipette saturated with Fast Green, to aid in later histological tract identification. The number of cells projecting to cervical and lumbar regions in the dorsal and ventral division of Deiters' nucleus did not differ significantly. An unexpectedly large number of MVST units was found in the descending nucleus. Some MVST units projected to the lumbar cord but in both the medial and descending nuclei, projections to the cervical cord were in majority. Almost all spinal projecting vestibular neurons received labyrinthine input and more than half received somatosensory input. The units could be separated into several populations on basis of excitatory and inhibitory labyrinthine response latencies indicating multiple pathways. As regards labyrinthine-somatosensory integration the two tracts were found to be quite similar. The extent and complexity of labyrinthine-somatosensory convergence indicate the importance of feed-back mechanisms upon postural controls also at the level of the vestibular nuclei.

Action Potentials↗

PubMedDate not supplied

Semicircular canal orientation in the adult resting rabbit.

Photographs of rabbits in the alert resting position were used to record head position. Semicircular canals were surgically exposed and points measured along each canal were used to compute the best-fit plane using a least-squares method. Computations of mean best-fit planes showed that the horizontal canals were not carried horizontally in the rabbit. The anteromedial edges were superior by 16 degrees. The anterior canals were vertically oriented and made an angle of 43 degrees to the sagittal plane. The posterior canal was tipped in the anterior direction slightly and also made an acute angle (26 degrees) with the frontal plane. Rabbit semicircular canals deviated significantly from orthogonality. The range was 86 degrees (anterior canals) to 133 degrees (posterior canals). Thus, there were no co-planar canals. Such semicircular canal geometry has implications for the neural circuitry controlling posture in the rabbit.

Animals↗

PubMed1989

The effects of glycerol on vestibular function and the endolymphatic sac after pre-treatment with colchicine.

The endolymphatic sac (ES) is believed to absorb endolymph. Recent studies have suggested that the ES also has a secretory capacity, a function that may be related to the regulation of inner ear fluid volume and pressure. Other studies indicate that hyperosmolar substances, such as glycerol and urea, may initiate a secretion of glycoprotein into the ES. This function was suggested to be related to a regulatory function of the ES by which it can compensate for a decrease in endolymph pressure. In order to investigate this regulatory potential of the ES, the effect of glycerol on the ES was investigated with or without the presence of pharmacological inhibition of glycoprotein secretion through colchicine treatment. Animals treated in such a way showed marked signs of impaired inner ear function, including loss of postural control and loss of Preyer's reflex. Significant ultrastructural changes were noted in the endolymphatic sac suggesting a disturbed secretory activity. The results may indicate that the endolymphatic sac may actively respond to changes in endolymph homeostasis through secretion of macromolecular substances and that alterations in this secretion may lead to functional disturbances of the inner ear.

Animals↗

PubMed1996

Brief communication: bilateral footedness and task complexity.

The primary intent of this investigation was to determine if stabilizing complexity (postural control) influenced lower limb selection while performing a bilateral footedness task. Right- and left-footed subjects (as determined by a bilateral preference inventory) were asked to stand on one foot and tap a telegraph key with the opposite foot repeatedly. The bilateral task was conducted in two conditions of stabilizing complexity, with the intent to augment focus of attention between stabilizing and mobilizing limb: simple (lights on) and complex (limitation of visual cues). Results indicated that in both simple and complex conditions, 50% or more of subjects switched stabilizing limbs or showed no preference when comparing preference inventory behavior to experimental conditions, suggesting, in general, that foot preference may be in part dependent on the context of the task and not tied predominantly to biological theory.

Female↗

PubMed1997

Hypotension: a forgotten illness?.

Low blood pressure is a frequently encountered phenomenon in clinical practice. Few practitioners in the Western world however regard chronic low blood pressure as a genuinely pathological disease state. Evidence is emerging that chronic hypotension is associated with considerable morbidity in the community. It has recently been implicated as the causative mechanism in patients with the chronic fatigue syndrome. Identification of low blood pressure can prove probjlematic, so ambulatory blood pressure monitoring may prove a more reliable method both for determining mean blood pressure levels and for identifying episodes of marked hypotension. Low blood pressure is broadly divided into two categories, chronic constitutional hypotension and hypotension associated with abnormal postural control. The causes are examined and the clinical presentations are discussed. An approach to investigation and diagnosis is outlined, and current options regarding treatment and management are described. The clinical spectrum of low blood pressure is wide. From young patients with vagally mediated syncope or patients with iatrogenic hypotension to elderly patients with autonomic degenerative conditions, there exists a substantial body of patients with potentially avoidable or treatable morbidity. Such a group requires more rigorous scientific investigation and a more sympathetic clinical approach.

Journal Article↗

PubMed2000

Short-term analysis of the relationship between blood pressure and urinary sodium excretion in normotensive subjects.

The aim of this study was to investigate whether, in the short term, physiological blood pressure changes are coupled with changes in urinary sodium excretion in normotensive subjects, maintained at fixed sodium intake and under controlled postural and behavioural conditions. Twelve normotensive subjects were recruited. For each subject, seven urine samples were collected at fixed time intervals during an overall 26 h period: late afternoon (16.00-20.00 hours), evening (20.00-24.00 hours), night (24.00-06.00 hours), quiet wakefulness (06.00-09.00 hours), morning (09.00-12.00 hours), post-prandial (12.00-15.00 hours) and afternoon (15.00-18.00 hours). Blood pressure was monitored by an ambulatory blood pressure device during the whole 26 h period. Each urine sample was used to measure urinary sodium excretion and glomerular filtration rate (creatinine clearance). Blood pressure, heart rate, urinary sodium excretion and glomerular filtration rate recorded in the daytime were higher than those measured during the night-time. A significant positive correlation between mean blood pressure and urinary sodium excretion was found during the night, over the whole 26 h period, and during two subperiods of the daytime: quiet wakefulness and the post-prandial period. The coefficient of the pressure-natriuresis curve was significantly decreased by postural changes. We conclude that, in normotensive subjects, blood pressure and urinary sodium excretion are coupled in the short term. The assumption of an upright posture can mask this relationship, presumably by activating neurohumoral factors.

Adult↗

PubMed2000

Falls in the elderly.

Falls are the leading cause of injury-related visits to emergency departments in the United States and the primary etiology of accidental deaths in persons over the age of 65 years. The mortality rate for falls increases dramatically with age in both sexes and in all racial and ethnic groups, with falls accounting for 70 percent of accidental deaths in persons 75 years of age and older. Falls can be markers of poor health and declining function, and they are often associated with significant morbidity. More than 90 percent of hip fractures occur as a result of falls, with most of these fractures occurring in persons over 70 years of age. One third of community-dwelling elderly persons and 60 percent of nursing home residents fall each year. Risk factors for falls in the elderly include increasing age, medication use, cognitive impairment and sensory deficits. Outpatient evaluation of a patient who has fallen includes a focused history with an emphasis on medications, a directed physical examination and simple tests of postural control and overall physical function. Treatment is directed at the underlying cause of the fall and can return the patient to baseline function.

Accidental Falls↗

PubMedDate not supplied

Ocular motility and visuo-spatial attention in children with periventricular leukomalacia.

Periventricular leukomalacia (PVL) is known to cause visual, motor, and cognitive impairments varying in their severity. Most studies focused on impairment at early ages. Little is known about the PVL's later outcome. Effects of neural plasticity are for instance insufficiently known to prognose precisely their behavioral outcome. It is even hard to determine the consequence of one defect on global development over time. Because of the established neural link between eye motion and space perception, 5-to-9 year-old PVL's were tested in visual detection, postural control, and space attention tasks. In this paper, discussion will focus on behavioral asymmetry, developmental outcome, and brain injury.

Attention↗

PubMed2000

[Study of click-induced vestibule-sternocleidomastoid reflex recorded with surface electromyography].

The otolithic organs serve to control posture and maintain the visual objective during linear accelerations. Recent experimental research in man and animals has suggested that it may be possible to explore the function of these organs by studying the vestibule-sternocleidomastoid reflex induced by high intensity clicks. The aim of the present work was to identify the parameters which are most reproducible in normal subjects and, therefore, best suited to this purpose. The instrument normally used to study evoked auditory potentials (ERA) was used to perform an electromyographic recording at the surface of the sternocleidomastoid muscle (SCM) and then average the electromyographic response to short clicks (0.1 ms) introduced through the headphones. In normal subjects clicks at an intensity of 85-100 dB HL evoked a reproducible electromyographic response in the venter of the SCM muscle with an average latency of 8.75 ms. The latency parameter proved to present the most suitable characteristics for possible clinical use. The possibility of using this method to study human vestibular lesions is certainly enticing although further research is needed to better characterize the precise site of origin for the vestibule-sternocleidomastoid reflex.

Adult↗

PubMed1998

Potential targets for skeletal muscle impairment by hypogravity: basic characterization of resting ionic conductances and mechanical threshold of rat fast- and slow-twitch muscle fibers.

Prolonged hypogravity such as during space flights affects skeletal muscle function by inducing postural changes as well as reduced muscle strength and locomotion capacity. Also in rats, space flight as well as useful models of groundbased hypogravity induce marked atrophy in the slow-twitch soleus (SOL) muscle as opposed to slight or none in the fast-twitch ones such as extensor digitorum longus (EDL). Biochemical and histological studies on hindlimb suspended animals, showed a hypogravity-induced impairment of muscle function involving the transition of slow-twitch muscle type, responsible for postural control, toward the fast-twitch phenotype by modification of excitation-contraction pattern. In slow muscles of rats, hindlimb suspension induced upregulation of the fast isoform of myosin heavy-chain and increased expression of fast Ca2+ pump mRNA and protein, which is consistent with the increased Ca(2+)-dependent ATPase activity and the speeding of muscle relaxation, typical of fast muscles. Little is known about the modifications induced by hypogravity in the sarcolemmal ion channels function, which controls the pattern of muscle excitability and contractility. The normally high resting chloride conductance, which is required for the electrical stabilization of mammalian muscle fibers, may be a target of hypogravity modifications since a pharmacological block of this parameter determines, though an increase of excitability, the transition of the fast-twitch muscle phenotype toward the slow one either in adult or in developing rats. Hypogravity also induced increased expression of dihydropyridine receptors in soleus muscle, that are normally lower than that found in the fast ones. In this study, we characterized the electrical and contractile properties of rat extensor digitorum longus (EDL) and slow-twitch soleus SOL muscles fibers at the aim to better understand the molecular mechanisms leading to fiber transition.

Animals↗

PubMed1999

Elicitation of otolithic nystagmus by step and sinusoidal modes of linear acceleration (Gy) in humans.

The vestibular otolith organ, a sensor of linear acceleration, is known to be important not only for posture control and spatial orientation, but also for eye movement control. Niven et al. (1966) have reported that linear acceleration along the Y (left-right, interaural) head axis by using a linear track induces compensatory horizontal eye movements including nystagmus. This was confirmed by several authors using a linear accelerator and a parallel swing. We have already found that a step mode of Gy linear acceleration is useful to elicit otolithic nystagmus and that nystagmus have directional preponderance (DP) (Mori and Katayama, 1998). In the present report, we attempted to compare two modes of acceleration, step and sinusoidal, in nystagmic elicitation induced by linear acceleration.

Acceleration↗

PubMed1998

[Masticatory muscles. Part VIII. Reflexes in the masticatory system].

A reflex is an involuntary response on a specific nerve stimulus. Several types of receptors are present in the masticatory system which can be involved in reflex activity. A short mechanical tap on an incisor, for example, evokes a specific pattern of several so-called exteroceptive reflexes in the electromyographic (EMG) activity of jaw-closing muscles, which includes periods with decreased activity (inhibitory reflex) as well as increased activity (excitatory reflex). In this case, periodontal mechanoreceptors are detecting the stimulus. The second type of reflex that is dealt with is the jaw-jerk reflex as an example of a proprioceptive reflex. A transient increase in length of a jaw-closing muscle, detected by length sensors (muscle spindles), evokes an excitatory reflex in the EMG. Dependent on the motor task, the amplitude of both reflexes is modified. The various reflex mechanisms play an important role in normal physiological functions such as posture control and chewing.

Electromyography↗

PubMed2002

[Whiplash injuries--a psychosomatic perspective].

BACKGROUND: Psychosocial impairment after whiplash injury could be extensive; presumably about 15% of whiplash patients suffer from long lasting disabling health problems and about 5% do not return to work. MATERIAL AND METHODS: A PubMed search of all available literature on whiplash and whiplash-associated disorders was performed. RESULTS: Psychosocial impairment following whiplash injury is influenced by vulnerability factors, the biomechanical trauma and factors affecting symptom formation. Vulnerability factors indicating a poorer prognosis include low mental abilities, previous mental illness, old age and female sex, pre-existing cervical degenerative changes, narrow spinal canal and high neurobiological reactivity to sustained activation. The actual physical trauma consists of a nonphysiologic kinematic response in the cervical column, which may induce stress in neural structures, facet joints and musculature. Activation of reflex connections may lead to disturbances in the posture control and autonomic system. Trauma-related prognostic factors include head position at impact and degree of acute psychological stress reactions. Manual work, expectation of disability and an ongoing compensation claim case seem to be important moderator variables affecting symptom formation. INTERPRETATION: An integrated psychosomatic model is needed to explain psychosocial impairment after whiplash injury as presented.

Accidents, Traffic↗

PubMed2003

[Medical care and support in school and community life to very severe neurologically-impaired children--advance and problems in medical, educational and social management for improvement of QOL].

With an increasing number of children with severe neurological impairment living in their houses, there is growing demand for medical care and support in school and community life. In such cases, respiratory disorder, gastro-esophageal reflux and dysphagia are closely related. To improve these disorders, appropriate rehabilitation and daily managements, such as posture control, are important as well as medical and surgical treatment. Social and educational support is also necessary for improvement of the QOL of these children and their family. For example, daily medical care such as tube feeding and sputum suctioning should be provided by school staffs. Pediatric neurologists should actively participate in such educational and social activities.

Cerebral Palsy↗

PubMed2003

[Treatment of respiratory disturbance in children with severe physical disabilities to improve their quality of life].

Children with severe physical disabilities frequently have respiratory problems which affect their quality of life (QOL). They commonly stem from central nervous system dysfunctions and/or severe motor disabilities, and consist of various impairments deriving primarily from central and motor dysfunctions, such as dysmyotonia, deformation, dysphagia, and gastro-esophageal reflux (GER), which often influence each other and result in respiratory insufficiency without adequate interventions. Aging is also an important factor to worsen respiratory involvements and to change their underlying pathophysiology gradually, even if the primary cause of the disability is non-progressive. A key to effective treatment and improvement of their QOL is to understand the pathophysiology. Evaluation is primarily based on regular physical examination. Other examinations include blood sampling to examine inflammation, nutritional state and blood gas analysis, round-the-clock SpO2 and TcPCO2 or EtCO2 monitoring, chest X ray and computed tomography, polysomnography, laryngoscopy, bronchoscopy, evaluation of swallowing function, and evaluation of GER. Postural control, relaxation, respiratory physiotherapy, and treatment of dysphagia are the most important and common therapeutic procedures. Treatment of GER, treatment of upper airway obstruction, oxygen therapy, tracheostomy, or mechanical ventilation may be needed. It is also important to take into account the possibility that the treatment procedures themselves could affect the patient's QOL. Counseling should be performed before and throughout the treatment process about how patient's and family's everyday life will be influenced positively and negatively by the treatment, and a multidisciplinary team should support all aspects of their needs.

Cerebral Palsy↗