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PubMedDate not supplied

Impairment of learning the voluntary control of posture in patients with cortical lesions of different locations: the cortical mechanisms of pose regulation.

The process of learning to produce voluntary changes in the position of the center of pressures using biological feedback was studied by stabilography in patients with hemipareses due to cerebrovascular lesions in the zone supplied by the middle cerebral artery. There were significant impairments to learning in all groups of patients, who had lesions in different sites, demonstrating that cortical mechanisms are involved in learning to control posture voluntarily. These studies showed that patients with lesions in the right hemisphere had rather greater deficits in performing the task than those with lesions in the left hemisphere. There were significant differences in the initial deficit in performing the task on the first day of training depending on the side of the lesion. All groups of patients differed from healthy subjects in that significant learning occurred only at the initial stages of training (the first five days). Learning at the initial stage in patients with concomitant lesions of the parietal-temporal area and with combined lesions with motor, premotor, and parietal-temporal involvement was significantly worse and the level of task performance at the end of the initial stage was significantly worse than in patient with local lesions of the motor cortex. The level of learning was independent of the severity of the motor deficit (paresis, spasticity), but was associated with the severity of impairment of the proprioceptive sense and the severity of disruption to the upright posture (asymmetry in the distribution of support pressures, amplitude of variation in the position of the center of pressures). The learning process had positive effects on the severity of motor impairment and on the asymmetry of the distribution of support pressures in the standing posture. Reorganization of posture during bodily movements occurred mainly because of impairment to the developed "non-use" stereotype of the paralyzed lower limb.

Biomechanical Phenomena↗

PubMed2003

Postural stability in children with autism spectrum disorder.

Maintaining upright posture is a complex process involving multiple afferent systems. The aim of this study was to measure the postural stability of children with Autism Spectrum Disorder (ASD) compared with children with typical neurodevelopment and to measure the relative contributions of the visual, somatosensory, and vestibular afferent systems in each group. Eight boys with ASD and eight age-, race-, and gender-matched controls participated in this study using force platform technology with customized software to measure postural sway under conditions designed to eliminate or modify visual and somatosensory input. Children with ASD had significantly larger sway areas under all test conditions in which afferent input was modified. These results are consistent with a deficit in the integration of visual, vestibular, and somatosensory input to maintain postural orientation.

Autistic Disorder↗

PubMed1999

Postural coordination modes considered as emergent phenomena.

The coordination of multiple body segments (torso and legs) in the control of standing posture during a suprapostural task was studied. The analysis was motivated by dynamical theories of motor coordination. In 2 experiments it was found that multisegment postural coordination could be described by the relative phase of rotations around the hip and ankle joints. The effective length of the feet, the height of the center of mass, and the amplitude of head motions in a visual tracking task were varied. Across these variations, 2 modes of hip-ankle coordination were observed: in-phase and anti-phase. The emergence of these modes was influenced by constraints imposed by the suprapostural tracking task, supporting the idea that such tasks influence postural control in an adaptive manner. Results are interpreted in terms of a dynamical approach to coordination in which postural coordination modes can be viewed as emergent phenomena.

Adult↗

PubMed1986

Morphine subtracts subcomponents of haloperidol-isolated postural support reflexes to reveal gradients of their integration.

Although cataleptic rats do not spontaneously orient, scan, or walk, they will cling, stand, right themselves in the air, and resist being displaced from a stable position (Schallert, Whishaw, De Ryck, & Teitelbaum, 1978). Morphine produces a state of immobility in which all reflexes used for stable static support (e.g., standing, righting, clinging, and bracing) appear to be inhibited (De Ryck, Schallert, & Teitelbaum, 1980). Addition of morphine to haloperidol abolished or reduced those reflexes used to defend against slow postural displacements (e.g., bracing) but left intact those used to protect against fast postural displacements (e.g., righting in the air). However, although intact, these responses to fast postural displacements were completely abolished by labyrinthectomy, showing that they were controlled only by vestibular inputs. During recovery from morphine's effects, the responses to slow postural displacements reemerged, revealing fractional subcomponents. Furthermore, the reorganization of the subcomponents proceeded along specific body gradients; for example, bracing and standing reemerged caudorostrally, while at the same time, righting and clinging reemerged rostrocaudally.

Animals↗

PubMed1995

Planning reaches by evaluating stored postures.

This article describes a theory of the computations underlying the selection of coordinated motion patterns, especially in reaching tasks. The central idea is that when a spatial target is selected as an object to be reached, stored postures are evaluated for the contributions they can make to the task. Weights are assigned to the stored postures, and a single target posture is found by taking a weighted sum of the stored postures. Movement is achieved by reducing the distance between the starting angle and target angle of each joint. The model explains compensation for reduced joint mobility, tool use, practice effects, performance errors, and aspects of movement kinematics. Extensions of the model can account for anticipation and coarticulation effects, movement through via points, and hierarchical control of series of movements.

Biomechanical Phenomena↗

PubMed2004

Adaptive utilization of optical variables during postural and suprapostural dual-task performance: comment on Stoffregen, Smart, Bardy, and Pagulayan (1999).

T. A. Stoffregen, L. J. Smart, B. G. Bardy, and R. J. Pagulayan (1999) combined a postural task (upright stance) with a suprapostural task (visual fixation) to show that sway variability was not driven by optic flow in a task-independent manner (autonomous control) but governed by the demands of the supra-postural task (facilitatory control). The present study used a novel combination of Stoffregen et al.'s task conditions but obtained clear evidence of autonomous control and no indication of facilitatory control. The theoretical adequacy of the stabilization-by-looking versus stabilization-of-looking contrast was examined, as was emerging evidence that posture control and common cognitive tasks place concurrent demands on the same capacity-limited resources. An adaptive resource-sharing view of postural-suprapostural multitasking was proposed as an alternative to both the autonomous- and facilitatory-control views.

Adaptation, Ocular↗

PubMed2006

Turning configural processing upside down: part and whole body postures.

Like faces, body postures are susceptible to an inversion effect in untrained viewers. The inversion effect may be indicative of configural processing, but what kind of configural processing is used for the recognition of body postures must be specified. The information available in the body stimulus was manipulated. The presence and magnitude of inversion effects were compared for body parts, scrambled bodies, and body halves relative to whole bodies and to corresponding conditions for faces and houses. Results suggest that configural body posture recognition relies on the structural hierarchy of body parts, not the parts themselves or a complete template match. Configural recognition of body postures based on information about the structural hierarchy of parts defines an important point on the configural processing continuum, between recognition based on first-order spatial relations and recognition based on holistic undifferentiated template matching.

Depth Perception↗

PubMed1996

Postural asymmetries and language lateralization in humans (Homo sapiens).

Is hemispheric specialization for speech more closely related to left hemisphere specialization for manual skill and sequencing, as is usually supposed, or to control of asymmetries in whole body posture, as recent findings of right-handedness in nonhuman primates suggest? This question can be evaluated in the 10% of humans who have mixed handedness and footedness. Footedness entails postural asymmetry, and persons with mixed limb preferences often prefer the hand ipsilateral to the preferred foot in asymmetrical actions for which whole body postural adjustments are obligatory (e.g., throwing). The dichotic listening test , and indicator of language laterality, was administered to 4 groups of 48 persons with the 4 possible combinations of hand and foot preference. As in 2 past studies, language lateralization was somewhat more strongly related to postural asymmetries than to asymmetries in manual skill and sequencing.

Adolescent↗

PubMed1991

The effect of posture on the intraocular pressure and pulsatile ocular blood flow in patients with non-arteritic anterior ischaemic optic neuropathy.

Intraocular pressure (IOP) and pulsatile ocular bloodflow (POBF) have been recorded in 15 patients with unilateral non-arteritic anterior ischaemic optic neuropathy (na-AION) and in 28 healthy subjects of comparable age. Measurements were obtained in both the upright and lying postures with a pneumotonometer linked to a Langham ocular bloodflow system. By comparison with the healthy subjects, patients with na-AION were found to have a significantly greater postural pressure change in IOP (3.9 +/- 0.4 mmHg in the affected eye and 3.6 +/- 0.6 mmHg in the unaffected eye of the patients with na-AION compared to 2.2 +/- 0.4 mmHg in the right eye of the healthy subjects P less than 0.01 and less than 0.05 respectively). There was no significant difference between the IOP in the affected and unaffected eyes of patients with na-AION nor between this group and the healthy subjects in either posture. Pulsatile ocular bloodflow measurements were similar in both groups and in both eyes of the patients with na-AION. In both groups POBF fell significantly on lying down (healthy right eyes -84 +/- 16 ul/min p less than 0.01, na-AION affected eye -84 +/- 24 ul/min p less than 0.01, unaffected eye -83 +/- 26 ul/min p less than 0.001). These figures represent decrements of 19% in all groups. These findings suggest that assumption of the supine posture may be associated with a reduction in the pulsatile component of ocular perfusion. The importance of this in the pathogenesis of na-AION is discussed.

Adult↗

PubMed2006

Effect of obesity on posture and hip joint moments during a standing task, and trunk forward flexion motion.

OBJECTIVE: Effects of obesity on trunk forward flexion motion in sitting and standing, and postural adaptations and hip joint moment for a standing work task. DESIGN: Cross-sectional comparison of obese and normal weight groups. SUBJECTS: Ten obese subjects (waist girth 121.2+/-16.8 cm, body mass index (BMI) 38.9+/-6.6 kg m(-2)) and 10 age- and height-matched normal weight subjects (waist girth 79.6+/-6.4 cm, BMI 21.7+/-1.5 kg m(-2)). METHODS: Trunk motion during seated and standing forward flexion, and trunk posture, hip joint moment and hip-to-bench distance during a simulated standing work task were recorded. RESULTS: Forward flexion motion of the thoracic segment and thoracolumbar spine was decreased for the obese group with no change in pelvic segment and hip joint motion. Obese subjects showed a more flexed trunk posture and increased hip joint moment and hip-to-bench distance for a simulated standing work task. CONCLUSIONS: Decreased range of forward flexion motion, differing effects within the trunk, altered posture during a standing work task and concomitant increases in hip joint moment give insight into the aetiology of functional decrements and musculoskeletal pain seen in obesity.

Adult↗

PubMed1985

Intra-individual variability in postural blood pressure in the elderly.

Orthostatic hypotension, an age-related phenomenon, has been associated with hypertension and body weight variability. To evaluate the relative contributions of blood pressure elevation and abnormalities in extracellular volume regulation to orthostatic hypotension, elderly institutionalized subjects (mean age = 87 +/- 7 years), taking no cardiovascular medications, underwent measurement of body weight (n = 15) and first morning supine and standing blood pressures (n = 19), 12-13 times per subject over a 2-4 week period. There was a wide day-to-day variability in postural systolic blood pressure change (coefficient of variation = 533%) and a strong negative correlation between each day's postural change in systolic blood pressure and basal supine blood pressure (r = -0.55, P less than 0.0001). There was no association between postural blood pressure change and heart rate response or body weight changes, which were very small over the duration of the study (coefficient of variation = 0.6%). Elderly individuals have intact homeostatic mechanisms for the control of standing pressure when basal blood pressure is normal. Postural hypotension in the elderly is a variable phenomenon related to elevations in basal blood pressure.

Age Factors↗

PubMed1987

Effect of dietary sodium chloride and posture on plasma immunoreactive atrial natriuretic peptide concentrations in man.

The effect of changes of dietary sodium chloride intake and posture on plasma atrial natriuretic peptide concentration and renal function was studied in 11 normal human volunteers. Plasma atrial natriuretic peptide concentration was higher in the upright posture on a high than it was on a medium or low salt diet. On the medium and high but not on the low salt diet the concentration increased significantly on adoption of the supine posture. Creatinine, sodium, lithium and fractional lithium clearances, fractional distal sodium excretion and total distal water and sodium reabsorption, which were estimated by the lithium clearance technique, were significantly higher on the high than on the low salt diet. The medium salt intake gave intermediate values. Heart rate while upright was significantly higher on the low than on either the medium or the high salt diets. Systolic blood pressure was unaffected by salt intake. Diastolic blood pressure in the supine position was significantly higher on the low than on the medium or high salt diets. Both plasma noradrenaline concentrations and plasma renin activity were significantly higher on the low than on the high salt diet. Values on the medium salt intake were intermediate. Plasma concentrations of both hormones were higher in the upright than in the supine posture on all three salt intakes. The data are consistent with the hypothesis that atrial natriuretic peptide contributes to the cardiovascular and renal adjustments to changes in dietary sodium chloride, and the possible role of the peptide is discussed.

Adult↗

PubMed1990

Postural vasoconstriction in women during the normal menstrual cycle.

1. Postural vasoconstriction in the foot was examined in 15 women during the menstrual, follicular and luteal phases of the menstrual cycle, and in 13 age-matched men on two separate occasions, in a constant-temperature environment (22 degrees C). 2. Skin blood flow was measured using laser Doppler flowmetry with the subject lying down, first with the foot maintained at heart level, then with the foot lowered passively 50 cm below the heart. In six of the women, at the time of experiment, serum oestradiol and progesterone were determined by radioimmunoassay. In four women and three men, foot swelling rate was also measured in the dependent foot using a strain gauge plethysmograph in addition to the postural changes in flow. At each visit, in all subjects, arterial blood pressure, heart rate, body temperature, foot skin temperature and body weight were also recorded. 3. The men showed no significant changes in all the variables assessed. In contrast, in women during the luteal phase diastolic and mean arterial pressures were significantly reduced, whereas heart rate, body temperature, foot skin temperature and body weight were significantly increased, as compared with the follicular and menstrual phases of the cycle. 4. During the follicular phase, when oestradiol concentration was high, there were significant reductions in dependent flow and foot swelling rate associated with a significantly augmented postural fall in flow, whereas during the luteal phase, when both oestradiol and progesterone levels were high, there were significant increases in dependent flow and foot swelling rate associated with a significantly impaired postural fall in flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

Pressor response to a postural change in cirrhosis: an experimental study in the CCl4-treated rat.

1. Systemic hypotension, blunted cardiovascular responsiveness to noradrenaline and an abnormal hypertensive pressor response to a postural change have been described in cirrhotic patients. 2. We have examined the role of blunted responsiveness in these abnormalities by studying basal arterial blood pressure and its response to a postural change (vertical head-up 90 degrees tilting) in conscious and pithed CCl4-treated (cirrhotic) rats, as well as assessing the pressor response to noradrenaline in vivo and the vascular contractile response to noradrenaline in vitro. 3. A diminished hypotensive response to a change in posture was found in pre-cirrhotic portal hypertensive rats, whereas an inverted hypertensive pressor response in the face of systemic hypotension occurred in the cirrhotic rats with portal hypertension. 4. The inverted pressor response was abolished in the pithed portal hypertensive cirrhotic rats. 5. The pressor response to noradrenaline in vivo in conscious cirrhotic rats and the vascular contractile responsiveness to noradrenaline in vitro were intact. 6. We conclude that blunted responsiveness to noradrenaline is not a contributory factor to the development of systemic hypotension or the inverted pressor response to a change in posture in cirrhosis.

Animals↗

PubMed1994

Physiological and symptomatic responses to postural change in non-diabetic subjects during hypoglycaemia.

1. Insulin-induced hypoglycaemia is characterized by an autonomic disturbance which produces some of the symptoms of hypoglycaemia. How an additional autonomic stress like postural change may alter physiological responses and symptoms of hypoglycaemia is not known. In 10 healthy male subjects (mean age 24 years) we observed physiological and symptomatic responses to postural change during acute (20 min) and prolonged (60 min) hyperinsulinaemic (60 m-units min-1 m-2) hypoglycaemia (2.5 mmol/l) and euglycaemia (4.5 mmol/l), and placebo control (saline). 2. In all studies standing increased plasma catecholamines (adrenaline, P < 0.001; noradrenaline, P < 0.0001), blood pressure (P < 0.0001) and heart rate (P < 0.0001). Catecholamine responses to standing were augmented by acute hypoglycaemia (adrenaline, P < 0.005; noradrenaline, P < 0.01), but less so by prolonged hypoglycaemia (adrenaline, P < 0.05; noradrenaline, P < 0.05). Supine heart rate was higher before standing during prolonged hypoglycaemia (P < 0.05), but did not increase as much on standing when compared with acute hypoglycaemia and prolonged euglycaemia. 3. During acute hypoglycaemia, autonomic symptoms increased on standing, but during prolonged hypoglycaemia, in the presence of generally higher symptom scores, standing had no effect. Autonomic symptoms, with the exception of hunger, tended to decrease with time (P < 0.05) during prolonged hypoglycaemia. 4. To conclude, posture does modify the catecholamine and symptomatic responses to hypoglycaemia, but this effect is dependent on the duration of hypoglycaemia. Hypoglycaemia and hyperinsulinaemia had little or no effect on the cardiovascular responses to changing posture.

Acute Disease↗

PubMed2006

Sagittal spinal posture in relation to craniofacial morphology.

OBJECTIVE: The aim of this study is to determine correlations between the parameters of body posture in the sagittal profile and sagittal jaw position by obtaining objective and valid three-dimensional measurements of the dorsal profile by means of rasterstereography. MATERIALS AND METHODS: Fifty-three adults with Class II or III malocclusions were examined, and six angular parameters were determined. For the sagittal analysis of body posture, the Fleche Cervicale and Lombaire as well as trunk inclination were evaluated. RESULTS: Statistically significant correlations (P < .05) were found between Facial Axis and Fleche Cervicale, Mandibular Plane angle and Fleche Cervicale, and Facial Depth and the Fleche Cervicale. CONCLUSIONS: It can be concluded that the mandible seems to have a greater effect on body posture than other craniofacial parameters. As a clinical result of this study, patients with severe malocclusions should be examined interdisciplinarily before orthognathic surgery is performed to minimize postural influence on the altered jaw relationship after surgery.

Adult↗

PubMed1999

Postural responses to combined vestibular and hip proprioceptive stimulation in man.

Vestibular-proprioceptive interaction in human postural control in the frontal plane was studied by analysing the lateral body sway evoked in a standing subject by a weak, near-threshold galvanic vestibular stimulation combined with a balanced, bilateral vibration of the medial gluteus muscles. The intensities of the stimuli were adjusted so that none of them produced a consistent postural response when delivered alone. The pattern of the lateral body sway evoked by the combined stimulation was compared with postural responses to suprathreshold vestibular stimulation and asymmetric (unilateral) vibration of the hip abductors. During the vestibular stimulation alone the head movement started earlier and was larger than movement of the hip. During unilateral vibration the head movement was delayed with respect to the hip movement and the amplitude of head deviation was less than that of the hip. The pattern of postural response to combined vestibular stimulation and balanced vibration resembled that observed under unbalanced, unilateral vibration in terms of both the latencies and amplitudes of deviation of the body segments from their respective baseline positions. It is suggested that the asymmetric vestibular signal provided by galvanic stimulation of the labyrinth introduces a bias into the reference frame for central interpretation of proprioceptive signals so that a symmetric proprioceptive input gives rise to a lateral body sway when referenced to an asymmetric vestibular input.

Adult↗

PubMed2001

Is sinus node modification appropriate for inappropriate sinus tachycardia with features of postural orthostatic tachycardia syndrome?

Inappropriate sinus tachycardia and postural orthostatic tachycardia are ill-defined syndromes with overlapping features. Although sinus node modification has been reported to effectively slow the sinus rate, long-term clinical response has not been adequately assessed. Furthermore, whether patients with postural orthostatic tachycardia would benefit from sinus node modification is unknown. The study prospectively assessed the short- and long-term clinical outcomes of seven consecutive female patients with postural orthostatic tachycardia syndrome and inappropriate sinus tachycardia who were treated with sinus node modification. The study was conducted in a tertiary care center. The electrophysiological and clinical responses were prospectively assessed as defined by autonomic function testing, including Valsalva maneuver, deep breathing, tilt table testing, and quantitative sudomotor axonal reflex testing. Among the study population (mean age was 41+/-6 years), 5 (71%) patients had successful sinus node modification. At baseline, heart rates were 101+/-12 beats/min before modification and 77+/-9 beats/min after modification (P = 0.001). With isoproterenol, heart rates were 136+/-9 and 105+/-12 beats/min (P = 0.002) before and after modification, respectively. The mean heart rate during 24-hour Holter monitoring was also significantly reduced: 96+/-9 and 72+/-6 beats/min (P = 0.005) before and after modification, respectively. Despite the significant reduction in heart rate, autonomic symptom score index (based on ten categories of clinical symptoms) was unchanged before (15.6+/-4.1) and after (14.6+/-3.6) sinus node modification (P = 0.38). Sinus rate can be effectively slowed by sinus node modification. Clinical symptoms are not significantly improved after sinus node modification in patients with inappropriate sinus tachycardia and postural orthostatic tachycardia. A primary subtle autonomic disregulation is frequently present in this population. Sinus node modification is not recommended in this patient population.

Adult↗