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PubMed2005

Perinatal development of the motor systems involved in postural control.

Motor behaviors of some species, such as the rat and the human baby, are quite immature at birth. Here we review recent data on some of the mechanisms underlying the postnatal maturation of posture in the rat, in particular the development of pathways descending from the brain stem and projecting onto the lumbar enlargement of the spinal cord. A short-lasting depletion in serotonin affects both posture and the excitability of motoneurons. Here we try to extrapolate to human development and suggest that the abnormalities in motor control observed in childhood--e.g. deficits in motor coordination--might have their roots in the prenatal period, in particular serotonin depletion due to exposure to several environmental and toxicological factors during pregnancy.

Animals↗
PubMed1992

[Visuo-postural control of schizophrenics--variations of sway area during horizontal eye movement].

In the present study, we investigated the neurological mechanism of commonly known specific or unnatural postures in schizophrenic patients. Using a gravimeter, body sway studied in 26 chronic schizophrenic patients, 10 schizoaffective disorder patients and 21 normal subjects. During eye fixation at a target while keeping an upright posture, schizophrenic patients presented a larger gravimetric area than the normal subjects and the patients with schizoaffective disorder. There was a negative correlation (r = -0.509) between the standard deviation of the sway gravimetric area during fixation and the dose of neuroleptics in schizophrenic patients, but no correlation was found in patients with schizoaffective disorder (r = -0.01), although they took neuroleptics in a similar regimen to that for the schizophrenics. There was no correlation between the standard deviation of the sway gravimetric area during fixation and the duration of illness. There was also no correlation between the former and the amplitude ratio of saccades during smooth pursuit eye movements. When horizontal eye movements pursuing the target were loaded in this experiment, both the normal subjects and the patients with schizoaffective disorder showed a decrease in a loaded gravimetric area and a tendency towards postural stabilization. However, schizophrenic patients having higher SANS scores (Andreasen) presented an increase in gravimetric area. This suggests that schizophrenic patients with higher SANS score may have organic cerebellar changes related to impairment of the mechanism of visual and postural coordinations.

Adult↗
PubMed2002

Subjective symptoms and postural control during a disabled submarine simulation.

To simulate conditions aboard a disabled submarine, 7 submariners were confined for 5 d to a normobaric environment of 16.75% O2, 2.5% CO2, 4 degrees C, and 85% relative humidity (RH). After 2 control days and 1 d of hypoxia, the remaining environmental conditions were imposed for the next 5 d, followed by 1 additional day of just hypoxia. Daily morning symptoms were assessed using the Environmental Symptoms Questionnaire (ESQ). Postural stability was determined on 4 occasions using a computerized balance system: control period, after 2.7 and 4.7 d of steady-state test conditions, and after 5.7 d (with return to normal ambient temp, RH, and CO2). Three balance tests were performed: eyes open, eyes closed, and a dynamic test. Postural stability deteriorated after 2.7 d (87% eyes open, P < 0.001 and 26% eyes closed, P = 0.01). ESQ symptom subsets for acute mountain sickness, exertion, fatigue, alertness, and ear/nose/throat were not significantly different. Cold symptom subsets were increased after 3-7 d (P < 0.001); distress and muscle discomfort subsets after 7 d (P = 0.02). Continued exposure to the combination of cold and hypoxia elicited subjective symptom changes and disturbances in postural stability that are statistically significant. These observations may be of practical importance when tasks aboard a disabled submarine involve balance and mobility.

Adult↗
PubMed2005

Postural control in children with developmental coordination disorder.

The development of static balance is a basic characteristic of normal motor development. Most developmental motor tests include a measure of static balance. Children with Developmental Coordination Disorder (DCD) often fail this item. This study reviews the balance problems of children with DCD. The general conclusion is drawn that under normal conditions static balance control is not a problem for children with DCD. Only in difficult, unattended, or novel situations such children seem to suffer from increased postural sway. These findings raise the question of what happens when balance is lost. The present study addresses the strength of correlation between the electromyography (EMG) and force plate signals in one-leg stance over epochs of stable and unstable balance. Four groups of children were involved in the study: two age groups and a group of children with DCD and balance problems and their controls. The results show a clear involvement of tibialis anterior and peroneus muscles in the control of lateral balance in all conditions and groups. The group of children with DCD and balance problems, however, showed a weaker coupling between EMG and corrective force compared with control children, indicating non-optimal balance control. An evaluation of the existing data in terms of evidence of specific structural deficits associated with DCD provided converging evidence that suggests cerebellar involvement.

Cerebellum↗
PubMed2001

Attentional demands for postural control: the effects of aging and sensory reintegration.

The aim of this experiment was to examine if, with aging, the task of reintegrating sensory information perturbs balance and requires additional attentional demand. Young adults and the elderly were asked to maintain a stable upright posture while standing on a force platform. Visual and ankle proprioceptive information were removed or perturbed and suddenly reinserted. Subjects also had to respond vocally as quickly as possible to an unpredictable auditory stimulus presented before or following a sensory reintegration and in control conditions. Reaction times to the auditory stimuli were used as an index of the attentional demands necessary for calibrating the postural system. Reintegration of proprioception in absence of vision and under vision yielded a faster center of pressure velocity for both groups. This effect, however, was more important for the elderly than the young adults. An increased attentional demand was observed for both groups when proprioceptive information had to be reintegrated in absence of vision. Altogether, these results propose that, for the elderly persons, postural contexts requiring a reweighting of sensory inputs could lead to increased risk for loss of balance and falls if insufficient attentional resources are allocated to the postural task.

Adult↗
PubMed2003

The influence of having the eyelids open or closed on undisturbed postural control.

To assess the possible interactions between the physiological mechanisms involved in eyelid closure and stance maintenance, 20 healthy adults were required to keep their eyes open in the dark (EOd), in daylight (EO), or to close them normally (EC), respectively and in random order. The analysis was focused on elementary motions computed from the complex centre of pressure (CP) trajectories, that is to say the vertical projection of the centre of gravity (CGv) and the difference between CP and CGv (CP-CGv). The results indicate that the mean amplitudes of the CP-CGv spectra are statistically reduced in EOd when compared to the EC condition. This diminution is thought to express a decrease in the level of activity of lower limb muscles involved in stance control. Interestingly, the CNS does not really seem to gain from these reduced horizontal accelerations at the CG level since the CGv amplitudes are in turn only slightly reduced. It can thus be hypothesised that, despite the fact that visual information in the EOd condition remains unavailable, the somesthetic cues continue to play a minor role in the detection-correction process aimed at controlling undisturbed stance.

Adult↗
PubMed1976

Static postural control in children.

The purpose of this study was to investigate "static" balance characteristics in four and eight year old children performing six developmental tasks leading to upright stance. The data were evaluated with electromyographic, center of gravity and photographic procedures. The results of the study indicated that the older age group of children demonstrated higher degrees of motor control in all the balance tasks involving upper and/or lower extremity support of the trunk. The eight year old children showed less postural sway, more definitive muscular localizations and smaller degrees of motor activity occurring during the execution of the developmental tasks.

Age Factors↗
PubMed1995

The role of haptic cues from rough and slippery surfaces in human postural control.

Haptic information is critically important in complex sensory-motor tasks such as manipulating objects. Its comparable importance in spatial orientation is only beginning to be recognized. We have shown that postural sway in humans is significantly reduced by lightly touching a stable surface with a fingertip at contact force levels far below those physically necessary to stabilize the body. To investigate further the functional relationship between contact forces at the hand and postural equilibrium, we had subjects stand in the tandem Romberg stance while being allowed physically supportive (force contact) and non-physically supportive (touch contact) amounts of index fingertip force on surfaces with different frictional characteristics. Mean sway amplitude (MSA) was reduced by over 50% with both touch and force contact of the fingertip, compared to standing without fingertip contact. No differences in MSA were observed when touching rough or slippery surfaces. The amplitude of EMG activity in the peroneal muscles and the timing relationships between fingertip forces, body sway and EMG activity suggested that with touch contact of the finger or with force contact on a slippery surface long-loop "reflexes" involving postural muscles were stabilizing sway. With force contact of the fingertip on a rough surface, MSA reduction was achieved primarily through physical support of the body. This pattern of results indicates that light touch contact cues from the fingertip in conjunction with proprioceptive signals about arm configuration are providing information about body sway that can be used to reduce MSA through postural muscle activation.

Adult↗