Vestibular control of posture and gait.
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Animals↗
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Results for “Postural control”
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[New trends in the treatment of sports injuries. Shortest possible immobilization. Teach the control of posture and movement].
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Athletic Injuries↗
A biofeedback study of postural sway.
An experiment was performed to control postural sway under auditory and visual feedback signals using a new apparatus. The subjects of 52 healthy high school girls were divided into 13 small groups. Each small group had four subjects who were assigned to one of the following four groups; 1) visual feedback group, 2) auditory feedback group, 3) auditory and visual feedback group, and 4) control group. Comparisons were made as to the duration of the green lamp being on, which indicated sway stayed around the initial central gravity. The results showed that auditory and visual feedback groups had a significant increase in the duration as compared to other three groups. With regard to the changes in the areas of postural sway, the largest increase was seen in the auditory and visual group. While the three feedback groups showed downward curves, the control group showed an upward one. Thus it is suggested that postural sway can be voluntarily controlled by a combination of an auditury feedback procedure and a visual feedback procedure, but not be either of them independently.
Adolescent↗
A biofeedback study of postural sway.
An experiment was performed to control postural sway under auditory and visual feedback signals using a new apparatus. The subjects of 52 healthy high school girls were divided into 13 small groups. Each small group had four subjects who were assigned to one of the following four groups; 1) visual feedback group, 2) auditory feedback group, 3) auditory and visual feedback group, and 4) control group. Comparisons were made as to the duration of the green lamp being on, which indicated sway stayed around the initial central gravity. The results showed that auditory and visual feedback groups had a significant increase in the duration as compared to other three groups. With regard to the changes in the areas of postural sway, the largest increase was seen in the auditory and visual group. While the three feedback groups showed downward curves, the control group showed an upward one. Thus it is suggested that postural sway can be voluntarily controlled by a combination of an auditory feedback procedure and a visual feedback procedure, but not by either of them independently.
Adolescent↗
Stereotactic posterioventral pallidotomy improves balance control as assessed by computerized posturography.
Postural instability is arguably the most debilitating symptom of Parkinson's disease (PD). Recently, posterioventral pallidotomy/pallidoansotomy (PVP) has been advocated to improve a multitude of symptoms associated with PD. Dyskinesias, rigidity and bradykinesia are the most talked about improved symptoms, but posture and gait are also affected after PVP. To analyze the effect of PVP on postural control, 14 patients with PD were prospectively studied using a computerized dynamic posturography machine. Seven males and 7 females underwent a total of 18 procedures, 6 left PVP, 6 right PVP, 2 bilateral and 2 had Vim thalamotomies in addition to PVP. Data were collected pre- and postoperatively after a 12-hour drug-free interval ('off' period) and 1-2 h after medications ('on' period). Postoperative analyses were performed between 1 and 3 months postoperatively. As a group, patients' balance, in the off period, improved after surgery in a dynamic setting. Prior to surgery, patients' anterior-posterior sway exceeded their stability limits (patient fell) on 31% of the trials. After surgery, the fall rate decreased to 23%. Anterior-posterior sway decreased significantly (p < 0.05) postoperatively when the platform was sway referenced. In comparing the effect of surgery in decreasing sway with that of medication preoperatively, improvement after surgery (off period) was better than the preoperative on period (p < 0.05). Patients also improved in ostoperative off state when compared to preoperative off state with the platform sway referenced (p < 0.05), controlling for improvement in dyskinesia-induced imbalance. In conclusion, PVP improves standing balance performance better than that achieved with medications preoperatively. Since central input parameters were improved, the mechanism of PVP may be centralized.
Aged↗
Synergistic influences of the striatum and the globus pallidus on postural and locomotor control.
We have investigated the role of the globus pallidus in locomotor and postural control in a previously established animal model of striatal dysfunction. Striatal efferent activity was suppressed by intracerebral infusions of antisense oligodeoxynucleotides targeted to the messenger RNA of the proto-oncogene, c-fos. This suppression produced robust circling behavior and an atypical expression of c-fos in the ipsilateral globus pallidus following psychostimulant challenge. Simultaneous infusions of antisense oligodeoxynucleotides into both the caudate-putamen and the ipsilateral globus pallidus produced an approximate threefold increase in the intensity of rotation elicited by D-amphetamine. Excitotoxic lesioning of the globus pallidus produced marked postural asymmetry and circling behavior upon stimulation. The intensity of this rotational behavior was similar to that produced by dual infusions of antisense oligodeoxynucleotides into the caudate-putamen and the globus pallidus, and was not further potentiated by suppression of striatal c-fos expression. These results demonstrate the importance of the globus pallidus in postural and motor control, and suggest that activation of this nucleus through a reduction in striatopallidal inhibition may function to balance the output activity of the basal ganglia.
Animals↗
An improved technique for the extraction of stochastic parameters from stabilograms.
An improved characterization of the dynamics of postural sway can provide a better understanding about the functional organization of the postural control system as well as a more robust tool for postural pattern recognition. To this aim, a novel parameterization was applied to the stabilogram diffusion analysis formerly proposed by Collins and De Luca [Collins JJ, De Luca CJ. Open-loop and closed-loop control of posture: a random-walk analysis of center-of-pressure trajectories. Exp Brain Res 1993;95:308-18] that considered the act of maintaining posture as a stochastic process. The main purpose of the present technique was to overcome some drawbacks of the model presented by Collins and De Luca that may restrain its potential application in clinical practice. The approach uses a unique non-linear model to describe the center of pressure (COP) dynamics that reduces the number of parameters and decreases their intra-subject variability; consequently, fewer trials are required to perform reliable estimates of stochastic parameters and this is of particular importance for subjects that cannot afford many repeated measurements because of age or pathology. Four new statistical mechanics parameters (NSMP) were computed on the log-log stabilogram diffusion plots and their estimates were compared in terms of reliability and sensitivity to the visual conditions with: (1) a minimal set of four summary statistic scores (SSS); and (2) the six statistical mechanics parameters (SMP) proposed by Collins and De Luca. All four NSMP showed at least a fair-to-good reliability (intraclass correlation coefficient, ICC>0.49) while SMP (ICC>0.20) showed some poor reliability. A better overall reliability was also observed with respect to SSS. Moreover, only NSMP had a similar score for eyes open and eyes closed conditions. Three out of four NSMP were also significantly sensitive to eyes open or closed conditions (P<0.001) while only three out of six SMP were sensitive to operating conditions (P<0.01).
Humans↗
A longitudinal study of neural maturation and early mother-infant interaction: a research note.
The development of postural control of the head and of looking towards and looking away from the mother is described; the age relationship between attainment of postural head control and looking towards the mother is investigated and the relation between smiling and "pleasure" vocalizations to looking towards and away is examined. Twelve normal, full-term mother-infant pairs participated in this home-based study. En face interaction was video-taped for maximally 15 min at 3, 6, 9, 12, 15 and 18 (or 21) weeks. We conclude that postural head control constitutes an important prerequisite for the emergence of socially directed behaviours during en face interaction.
Attention↗
Electromyographic and biomechanical characteristics of segmental postural adjustments associated with voluntary wrist movements. Influence of an elbow support.
This study re-investigates the characteristics of segmental postural adjustments associated with rapid mono-articular movements and analyses their dependence on initial postural conditions. Subjects performed rapid voluntary wrist flexions and extensions while maintaining their upper limb posture as stable as possible, with or without an elbow support. Surface electromyographic activity (EMG) was recorded from Flexor carpi ulnaris, Extensor carpi radialis, Biceps brachii, Triceps brachii and Deltoideus anterior. The kinematics of the three joints and kinetics in the support condition were also recorded. A planar mechanical model was used to determine the muscle torque required to keep the upper limb posture constant while performing wrist movements. All subjects showed anticipatory postural adjustments (APA) which, unlike those described for whole-body postural control, could not counteract in advance the perturbing inter-segmental forces created by the movement. Postural muscles were activated before the wrist movement with a chronology specific to the direction of the wrist movement. Some postural muscular activities anticipated that of the prime-movers in accordance with muscle torque, which had to be applied to the joints to keep the upper limb posture constant. These results reveal that the central nervous system (CNS) uses the same organization of the motor command for the control of both segmental and whole-body posture: APA and corrective postural adjustments (CPA), which are based on well-organized anticipatory postural muscle activities (APMA), except that APA can be non-efficient in segmental postural control. The presence or absence of an elbow support influenced the level of activation of postural muscle but not their chronology. This result suggests that the CNS uses a sequence of APMA: a postural muscle synergy which is predetermined as a function of the intended direction of the movements and modulates the gain towards certain muscles, in accordance with the gravitational effects, and supports reaction changes.
Action Potentials↗
The role of plantar cutaneous sensation in unperturbed stance.
Considerable evidence shows that sensation from the feet and ankles is important for standing balance control. It remains unclear, however, to what extent specific foot and ankle sensory systems are involved. This study focused on the role of plantar cutaneous sensation in quasi-static balance control. Iontophoretic delivery of anesthesia was used to reduce the sensitivity of the forefoot soles. In a follow-up experiment, subjects received intradermal injections of local anesthetic into the entire weight-bearing surface of the foot soles. Properties of the center-of-foot-pressure (COP) trajectories and ground reaction shear forces were analyzed using stabilogram-diffusion analysis and summary statistics. Effects of foot-sole anesthesia were generally small and mostly manifested as increases in COP velocity. Magnitude of COP displacement was unaffected by foot-sole anesthesia. Forefoot anesthesia mainly influenced mediolateral posture control, whereas complete foot-sole anesthesia had an impact on anteroposterior control. During bipedal stance, statistically significant effects of foot-sole anesthesia on COP were present only under eyes-closed conditions and included increases in COP velocity (11-12%) and shear force root-mean-square (13%), the latter indicating increases in body center-of-mass accelerations due to the foot-sole anesthesia. Similar effects were seen for unipedal stance in addition to an increase in anteroposterior COP median frequency (36%). Changes in stabilogram-diffusion parameters were confined to the short-term region suggesting that sensory information from the foot soles is mainly used to set a relevant background muscle activity for a given posture and support surface characteristic, and consequently is of little importance for feedback control during unperturbed stance. In general, this study demonstrates that plantar sensation is of moderate importance for the maintenance of normal standing balance when the postural control system is challenged by unipedal stance or by closing of the eyes. The impact of reduced plantar sensitivity on postural control is expected to increase with the loss of additional sensory modalities such as the concomitant proprioceptive deficits commonly associated with peripheral neuropathies.
Adult↗
Cat posture on a tilted platform.
The posture of cats trained to stand freely on a platform was studied during static tilts (up to +/- 30 degrees). Vertical projection of the center of mass on the support surface, as well as limb orientation in space and degree of limb flexion, varied minimally with platform tilt angle. The limbs' main axes were kept almost lined up with the vertical. This data indicates that postural control is simplified by strong internal constraints which limit the number of possible postural configurations. The mechanical advantages of this postural strategy are also considered. Finally, the data are discussed in the context of previously held views on the role of vestibular and neck reflex control of posture in intact animals.
Adaptation, Physiological↗
Transcutaneous electric nerve stimulation reduces neglect-related postural instability after stroke.
OBJECTIVE: To test the existence of a neglect-related component of postural imbalance in some stroke patients to determine whether neglect patients (1) show worse postural control compared with nonneglect patients and healthy subjects and (2) have latent postural capacities that could be unmasked by an appropriate somatosensory manipulation. DESIGN: Intervention study with and without transcutaneous electric nerve stimulation (TENS). SETTING: Rehabilitation center research laboratory. PARTICIPANTS: Twenty-two stroke patients (mean age, 58.3 +/- 2.5yr; average days since stroke, 83.2d) and 14 age-matched healthy subjects. Stroke patients were subdivided into 3 groups: 6 with spatial neglect and 16 without (8 with left lesion, 8 with right lesion). INTERVENTIONS: All participants were subjected to a dynamic balance task, performed while sitting for 8 seconds on a laterally rocking platform. Seated on this mobile support, they were asked to maintain actively an erect posture, sitting as still as possible. In patients, TENS was applied on the contralesional side of the neck during the postural task. An effective stimulation (intensity corresponding to the threshold of perception, TENS+) was compared with a placebo stimulation (.01 x threshold of perception, TENS-). MAIN OUTCOME MEASURES: Postural performance in each trial was monitored by using 2 criteria: the number of aborted trials caused by loss of balance, and the angular dispersion of the support oscillations in roll. The latter criterion, which increased with body instability, was defined as 2 standard deviations of the angular distribution. RESULTS: Patients showing neglect displayed pronounced postural instability compared with other patients and controls. Although dramatic postural instability in the neglect patients was spectacularly and systematically reduced with TENS, no effect was observed in patients without neglect. CONCLUSION: This is among the first studies to provide clinical evidence supporting the "postural body scheme" concept.
Adult↗
Auditory biofeedback substitutes for loss of sensory information in maintaining stance.
The importance of sensory feedback for postural control in stance is evident from the balance improvements occurring when sensory information from the vestibular, somatosensory, and visual systems is available. However, the extent to which also audio-biofeedback (ABF) information can improve balance has not been determined. It is also unknown why additional artificial sensory feedback is more effective for some subjects than others and in some environmental contexts than others. The aim of this study was to determine the relative effectiveness of an ABF system to reduce postural sway in stance in healthy control subjects and in subjects with bilateral vestibular loss, under conditions of reduced vestibular, visual, and somatosensory inputs. This ABF system used a threshold region and non-linear scaling parameters customized for each individual, to provide subjects with pitch and volume coding of their body sway. ABF had the largest effect on reducing the body sway of the subjects with bilateral vestibular loss when the environment provided limited visual and somatosensory information; it had the smallest effect on reducing the sway of subjects with bilateral vestibular loss, when the environment provided full somatosensory information. The extent that all subjects substituted ABF information for their loss of sensory information was related to the extent that each subject was visually dependent or somatosensory-dependent for their postural control. Comparison of postural sway under a variety of sensory conditions suggests that patients with profound bilateral loss of vestibular function show larger than normal information redundancy among the remaining senses and ABF of trunk sway. The results support the hypothesis that the nervous system uses augmented sensory information differently depending both on the environment and on individual proclivities to rely on vestibular, somatosensory or visual information to control sway.
Adaptation, Physiological↗
Multisensory control of human upright stance.
The interaction of different orientation senses contributing to posture control is not well understood. We therefore performed experiments in which we measured the postural responses of normal subjects and vestibular loss patients during perturbation of their stance. Subjects stood on a motion platform with their eyes closed and auditory cues masked. The perturbing stimuli consisted of either platform tilts or external torque produced by force-controlled pull of the subjects' body on a stationary platform. Furthermore, we presented trials in which these two stimuli were applied when the platform was body-sway referenced (i.e., coupled 1:1 to body position, by which ankle joint proprioceptive feedback is essentially removed). We analyzed subjects' postural responses, i.e., the excursions of their center of mass (COM) and center of pressure (COP), using a systems analysis approach. We found gain and phase of the responses to vary as a function of stimulus frequency and in relation to the absence versus presence of vestibular and proprioceptive cues. In addition, gain depended on stimulus amplitude, reflecting a non-linearity in the control. The experimental results were compared to simulation results obtained from an 'inverted pendulum' model of posture control. In the model, sensor fusion mechanisms yield internal estimates of the external stimuli, i.e., of the external torque (pull), the platform tilt and gravity. These estimates are derived from three sensor systems: ankle proprioceptors, vestibular sensors and plantar pressure sensors (somatosensory graviceptors). They are fed as global set point signals into a local control loop of the ankle joints, which is based on proprioceptive negative feedback. This local loop stabilizes the body-on-foot support, while the set point signals upgrade the loop into a body-in-space control. Amplitude non-linearity was implemented in the model in the form of central threshold mechanisms. In model simulations that combined sensor fusion and thresholds, an automatic context-specific sensory re-weighting across stimulus conditions occurred. Model parameters were identified using an optimization procedure. Results suggested that in the sway-referenced condition normal subjects altered their postural strategy by strongly weighting feedback from plantar somatosensory force sensors. Taking this strategy change into account, the model's simulation results well paralleled all experimental results across all conditions tested.
Adult↗
Effect of age on anticipatory postural adjustments in unilateral arm movement.
Aging is frequently accompanied by a deterioration in postural control. Accordingly, the elderly adopt postural strategies in order to maintain balance. The purpose of this study was to compare anticipatory postural adjustments in (healthy) 10 young and 10 elderly subjects using electromyography (EMG) and biomechanical parameters. While standing on a force platform, subjects performed voluntary, arm-raising movements under five conditions: self-paced at three different velocities, self-paced with load and an externally triggered, both at maximal velocity. The force platform provided information on vertical torque (T(z)) and center of pressure anteroposterior displacements (COP). EMG activity was recorded from the biceps femoris, quadriceps, tibialis anterior and soleus muscles. Voluntary movements were associated with an early COP backward shift and an anticipatory T(z). At low velocity, elderly subjects did not show any impairment in stability. At maximal velocity, T(z) was delayed in all conditions in the elderly group, whereas COP latency was reduced only in the self-paced condition without load. Despite this decrease in anticipation, the movement was performed at the same velocity as in younger subjects. The elderly adopted various muscle strategies in order to perform the same movement with less stability. In the self-paced condition, elderly subjects used a hip strategy, whereas young subjects used an ankle strategy. In the triggered condition, the strategy corresponded to increased activation of certain thigh muscles, rather than a sequence modification. Hence, local muscle strategies were used to counteract the overall delay in postural preparation revealed by biomechanical parameters.
Adult↗
Integration of posture and locomotion in acute decerebrate cats and in awake, freely moving cats.
For the past 10 years, our group has been engaged in the study of posture and locomotion in decerebrate cats and in freely moving awake cats. Our initial objective was to analyse the neuronal mechanisms of locomotion from a viewpoint of "postural control". Therefore, in this review, I have focussed my attention on two major control aspects of the brain stem; one related to the interaction of posture and locomotion; and the other to initiation of locomotion. It is apparent that elucidation of the second aspect is feasible. In Fig. 15, I have summarized all the neuronal structures that have been functionally identified as being actively involved in the regulation of posture and locomotion. Obviously, contribution of the cerebello-cerebral pathways and the basal ganglia to both the postural and to the locomotor control cannot be elucidated in decerebrate preparations (Fig. 15A). These contributions can, to a certain degree, be elucidated in intact awake cats (Fig. 15B). Although it is difficult to directly compare the results obtained in the decerebrate cats with those obtained in intact cats, it has been encouraging that the selective activation of certain neuronal structures within the brain stem allowed us to evoke comparable postural and locomotor changes in both groups of preparations. It can be expected that the knowledge obtained from studies of the cerebello-cerebral pathways and of the basal ganglia, together with those that can be further obtained from studies of the brain stem, should result in the elucidation of the two major control aspects of the brain stem described above. In this sense, both the models of the decerebrate locomotor preparation and the freely moving, awake cat seem to provide an unique opportunity to study the nature and the sources of command signals that set the postural and the locomotor synergies into a single functional synergy, and even to approach elucidation of the intriguing question as to how and where volitional control signals for initiating and/or halting locomotion are organized. More than 70 years have passed since the pioneer studies by Sherrington (1906) and by Graham Brown (1911, 1914) on postural control and on locomotion, as exemplified by "decerebrate reflex standing, and stepping" and the "central rhythmic generator" relating to locomotion. Based on these discoveries, Shik, Severin and Orlovsky (1966) have made a splendid breakthrough in a wide area of investigation relating to locomotion.(ABSTRACT TRUNCATED AT 400 WORDS)
Animals↗
Postural behaviour responses to visual stimulation in patients with vestibular disorders.
Patients with different vestibular disorders exhibit changes in postural behaviour when they receive visual stimuli, reproducing environmental stimulation. Postural control was studied using an AMTI Accusway platform, measuring the confidential ellipse (CE) and sway velocity (SV). Postural responses were recorded according to the following stimulation paradigm: i) without specific stimuli; ii) smooth pursuit with pure sinusoids of 0.2 Hz (foveal stimulation); and iii) optokinetic stimulation (retinal stimuli). Patients with central vestibular disorders (CVD), cerebellar damage and unilateral peripheral vestibular lesions (UPVL) in asymptomatic periods were studied. A group of normal subjects was studied as control. Signal processing was done with a scalogram by wavelets in order to observe the relation between time and frequency in postural control. While patients with CVD and cerebellar disease showed a significant increase in CE and SV in the three conditions of the paradigm compared to the normal group, the patients with UPVL showed no change. Wavelets processing showed that the main sway occurs in the Y axis (antero-posterior) and below at 0.4 Hz in normal subjects, while the CVD and cerebellar patients showed sway frequencies in both the X and Y axes. The clinical implications of these findings are discussed.
Adult↗
Postural reorganization following lower limb amputation. Possible motor and sensory determinants of recovery.
Postural control was assessed in persons with a unilateral lower limb amputation before and after their rehabilitation. The centre-of-pressure fluctuations during quiet upright standing on a dual-plate force platform were registered with and without visual information in order to identify relevant determinants of balance restoration. In addition, static (weight distribution) as well as dynamic (control activity) asymmetry characteristics were examined. Besides a small improvement in balance control with full visual information (fore-aft sway, p less than 0.06; lateral sway, p less than 0.05), there was a major decrease in visual dependency (fore-aft and lateral sway, p less than 0.05) indicating a somatosensory re-integration process. Postural asymmetry in comparison with matched control subjects was most apparent and only significant in dynamic terms and remained constant across rehabilitation. It is concluded that after a lower limb amputation a central reorganization of postural control takes place, in which sensory determinants of motor recovery may play a critical role.
Aged↗