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1.
Paraskevi Giagazoglou Ioannis G. Amiridis Andreas Zafeiridis Maria Thimara Vassiliki Kouvelioti Elefthrerios Kellis 《European journal of applied physiology》2009,107(5):571-579
The aim of the present study was to examine isokinetic and isometric strength of the knee and ankle muscles and to compare
center of pressure (CoP) sway between blind and sighted women. A total of 20 women volunteered to participate in this study.
Ten severe blind women (age 33.5 ± 7.9 years; height 163 ± 5 cm; mass 64.5 ± 12.2 kg) and 10 women with normal vision (age
33.5 ± 8.3 years; height 164 ± 6 cm; mass 61.9 ± 14.5 kg) performed 3 different tasks of increasing difficulty: Normal Quiet
Stance (1 min), Tandem Stance (20 s), and One-Leg Stance (10 s). Participants stood barefoot on two adjacent force platforms
and the CoP variations [peak-to-peak amplitude (CoPmax) and SD of the CoP displacement (CoPsd)] were analyzed. Sighted participants
performed the tests in eyes open and eyes closed conditions. Torque/angular velocity and torque/angular position relationships
were also established using a Cybex dynamometer for knee extensors and flexors as well as for ankle plantar and dorsiflexors.
The main finding of this study was that the ability to control balance in both anterior/posterior and medio/lateral directions
was inferior in blind than in sighted women. However, when sighted participants performed the tests blindfolded, their CoP
sway increased significantly in both directions. There were no differences in most isometric and concentric strength measurements
of the lower limb muscles between the blind and sighted individuals. Our results demonstrate that vision is a more prominent
indicator of performance during the postural tasks compared to strength of the lower limbs. Despite similar level of strength,
blind individuals performed significantly worse in all balance tests compared to sighted individuals. 相似文献
2.
R. D. Easton Anthony J. Greene Paul DiZio James R. Lackner 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1998,118(4):541-550
This study assessed whether stationary auditory information could affect body and head sway (as does visual and haptic information)
in sighted and congenitally blind people. Two speakers, one placed adjacent to each ear, significantly stabilized center-of-foot-pressure
sway in a tandem Romberg stance, while neither a single speaker in front of subjects nor a head-mounted sonar device reduced
center-of-pressure sway. Center-of-pressure sway was reduced to the same level in the two-speaker condition for sighted and
blind subjects. Both groups also evidenced reduced head sway in the two-speaker condition, although blind subjects’ head sway
was significantly larger than that of sighted subjects. The advantage of the two-speaker condition was probably attributable
to the nature of distance compared with directional auditory information. The results rule out a deficit model of spatial
hearing in blind people and are consistent with one version of a compensation model. Analysis of maximum cross-correlations
between center-of-pressure and head sway, and associated time lags suggest that blind and sighted people may use different
sensorimotor strategies to achieve stability.
Received: 11 November 1996 / Accepted: 29 July 1997 相似文献
3.
Dozza M Horak FB Chiari L 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2007,178(1):37-48
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. 相似文献
4.
Passive tactile sensory input improves stability during standing 总被引:5,自引:0,他引:5
Rogers MW Wardman DL Lord SR Fitzpatrick RC 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2001,136(4):514-522
The effects of passive tactile cues about body sway on stability during standing were evaluated in subjects with a wide range of sensorimotor and balance performance. Healthy young adults, diabetic subjects with varying degrees of peripheral sensory neuropathy and older subjects aged 70-80 years were studied. Body sway was measured when subjects stood on the floor and on a foam rubber mat, with or without an applied stimulus that rubbed on the skin at the leg or shoulder as the body swayed. The results show that this stimulus reduced body sway (mean reduction 24.8%+/-1.5) and thus had a stabilizing effect as big as vision or sensory information from the feet. The reduction in sway was not based on active touch. The stimulus was not restricted to a particular region of the body, but was more effective on the shoulder than the leg, and was more effective when standing with eyes shut or when standing on the foam mat. It was also most effective in those subjects who had the greatest sway during normal standing. Thus, the response appears to be graded with the amplitude of the stimulus. We concluded that, if passive sensory input about posture is available, the postural control process adapts to this input, modulating postural stabilizing reactions. 相似文献
5.
Alary F Goldstein R Duquette M Chapman CE Voss P Lepore F 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2008,187(4):587-594
Growing evidence suggests that blind subjects outperform the sighted on certain tactile discrimination tasks depending on
cutaneous inputs. The purpose of this study was to compare the performance of blind (n = 14) and sighted (n = 15) subjects in a haptic angle discrimination task, depending on both cutaneous and proprioceptive feedback. Subjects actively
scanned their right index finger over pairs of two-dimensional (2-D) angles (standard 90°; comparison 91–103°), identifying
the larger one. Two exploratory strategies were tested: arm straight or arm flexed at the elbow so that joint movement was,
respectively, mainly proximal (shoulder) or distal (wrist, finger). The mean discrimination thresholds for the sighted subjects
(vision occluded) were similar for both exploratory strategies (5.7 and 5.8°, respectively). Exploratory strategy likewise
did not modify threshold in the blind subjects (proximal 4.3°; distal 4.9°), but thresholds were on average lower than for
the sighted subjects. A between-group comparison indicated that blind subjects had significantly lower thresholds than did
the sighted subjects, but only for the proximal condition. The superior performance of the blind subjects likely represents
heightened sensitivity to haptic inputs in response to visual deprivation, which, in these subjects, occurred prior to 14 years
of age. 相似文献
6.
L. E. Sergio Stephen H. Scott 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1998,122(2):157-164
This study examines whether the kinematics of pointing movements are altered by the sensory systems used to select spatial
targets and to guide movement. Hand and joint paths of visually guided reaching movements of human subjects were compared
with two non-visual conditions where only proprioception was available: (1) movements of the same subjects with blindfolds,
and (2) movements by congenitally blind subjects. While hand-path curvatures were overall quite small, sighted subjects wearing
a blindfold showed a statistical increase in hand-path curvature compared with their visually guided movements. Blindfolded
subjects also showed greater hand-path curvature than blind subjects. These increases in hand-path curvature for blindfolded
subjects did not always lead to a decrease in joint-path curvature. While there were differences between blind subjects and
sighted subjects using vision for some movement directions, there was no systematic difference between these two groups. The
magnitude of joint-path curvature showed much greater variation than hand-path curvature across the movement directions. We
found variation in joint-path curvature to be correlated to two factors, one spatial and one geometrical. For all subject
groups, joint-path curvature tended to be smaller for sagittal-plane movements than for transverse or diagonal movements.
As well, we found that the magnitude of joint-path curvature was also related to the relative motion at each joint. Joint-path
curvature tended to increase when movements predominantly involved changes in shoulder angle and was minimal when movements
predominantly involved elbow motion. The consistently small curvatures of hand trajectory across blind and sighted subjects
emphasize the powerful tendency of the motor system to generate goal-directed reaching movements with relatively straight
hand trajectories, even when deprived of visual feedback from very early in life.
Received: 16 July 1997 / Accepted: 20 May 1998 相似文献
7.
In a well-executed golf swing, golfers must maintain good balance and precise control of posture. Golfing also requires prolonged
walking over uneven ground such as a hilly course. Therefore, repeated golf practice may enhance balance control and confidence
in the golfers. The objective is to investigate whether older golfers had better balance control and confidence than non-golfing
older, healthy adults. This is a cross-sectional study, conducted at a University-based rehabilitation center. Eleven golfers
and 12 control subjects (all male; mean age: 66.2 ± 6.8 and 71.3 ± 6.6 years, respectively) were recruited. Two balance control
tests were administered: (1) functional reach test which measured subjects’ maximum forward distance in standing; (2) sensory
organization test (SOT) which examined subjects’ abilities to use somatosensory, visual, and vestibular inputs to control
body sway during stance. The modified Activities-specific Balance Confidence (ABC) determined subject’s balance confidence
in daily activities. The golfers were found to achieve significantly longer distance in the functional reach test than controls.
They manifested significantly better balance than controls in the visual ratio and vestibular ratio, but not the somatosensory
ratio of the SOT. The golfers also reported significantly higher balance confidence score ratios. Furthermore, older adults’
modified ABC score ratios showed positive correlations with functional reach, visual and vestibular ratios, but not with somatosensory
ratio. Golfing is an activity which may enhance both the physical and psychological aspects of balance control. Significant
correlations between these measures reveal the importance of the balance control under reduced or conflicting sensory conditions
in older adults’ balance confidence in their daily activities. Since cause-and-effect could not be established in the present
cross-sectional study, further prospective intervention design is warranted. 相似文献
8.
M. Lacour J. Barthelemy L. Borel J. Magnan C. Xerri A. Chays M. Ouaknine 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1997,115(2):300-310
Vestibular inputs tonically activate the antigravitative leg muscles during normal standing in humans, and visual information
and proprioceptive inputs from the legs are very sensitive sensory loops for body sway control. This study investigated the
postural control in a homogeneous population of 50 unilateral vestibular-deficient patients (Ménière’s disease patients).
It analyzed the postural deficits of the patients before and after surgical treatment (unilateral vestibular neurotomy) of
their diseases and it focused on the visual contribution to the fine regulation of body sway. Static posturographic recordings
on a stable force-plate were done with patients with eyes open (EO) and eyes closed (EC). Body sway and visual stabilization
of posture were evaluated by computing sway area with and without vision and by calculating the percentage difference of sway
between EC and EO conditions. Ménière’s patients were examined when asymptomatic, 1 day before unilateral vestibular neurotomy,
and during the time-course of recovery (1 week, 2 weeks, 1 month, 3 months, and 1 year). Data from the patients were compared
with those recorded in 26 healthy, age- and sex-matched participants. Patients before neurotomy exhibited significantly greater
sway area than controls with both EO (+52%) and EC (+93%). Healthy participants and Ménière’s patients, however, displayed
two different behaviors with EC. In both populations, 54% of the subjects significantly increased their body sway upon eye
closure, whereas 46% exhibited no change or significantly swayed less without vision. This was statistically confirmed by
the cluster analysis, which clearly split the controls and the patients into two well-identified subgroups, relying heavily
on vision (visual strategy, V) or not (non-visual strategy, NV). The percentage difference of sway averaged +36.7%±10.9% and
–6.2%±16.5% for the V and NV controls, respectively; +45.9%±16.8% and –4.2%±14.9% for the V and NV patients, respectively.
These two distinct V and NV strategies seemed consistent over time in individual subjects. Body sway area was strongly increased
in all patients with EO early after neurotomy (1 and 2 weeks) and regained preoperative values later on. In contrast, sway
area as well as the percentage difference of sway were differently modified in the two subgroups of patients with EC during
the early stage of recovery. The NV patients swayed more, whereas the V patients swayed less without vision. This surprising
finding, indicating that patients switched strategies with respect to their preoperative behavior, was consistently observed
in 45 out of the 50 Ménière’s patients during the whole postoperative period, up to 1 year. We concluded that there is a differential
weighting of visual inputs for the fine regulation of posture in both healthy participants and Ménière’s patients before surgical
treatment. This differential weighting was correlated neither with age or sex factors, nor with the clinical variables at
our disposal in the patients. It can be accounted for by a different selection of sensory orientation references depending
on the personal experience of the subjects, leading to a more or less heavy dependence on vision. The change of sensory strategy
in the patients who had undergone neurotomy might reflect a reweighting of the visual and somatosensory cues controlling balance.
Switching strategy by means of a new sensory selection of orientation references may be a fast adaptive response to the lesion-induced
postural instability.
Received: 3 October 1996 / Accepted: 9 December 1996 相似文献
9.
Tactile sensitivity enhancement (TSE) observed in blind people is probably a result of intensified tactile training. Although many researchers consider TSE in the blind to be an example of use-dependent plasticity, it is unclear whether the effects of training (Braille reading) are specific, i.e. restricted to the trained function and hand, or if they are more general. To examine this issue further, blind Braille readers, low-vision subjects (Braille readers and non-Braille readers) and sighted controls were tested in two tasks: a texture task resembling the Braille system and a dissimilar groove orientation task. Braille readers, both blind and those with low vision, performed better in both tasks than low-vision non-Braille readers or sighted controls. However, the difference was significant only for the blind (more experienced) Braille readers. In the groove orientation task, the positive influence of training was detectable irrespective of the hand used in the test, but in the coarse texture task this influence was limited to the hand trained in Braille. Thus, it appears that tactile training is of significance in TSE but its effects are, to a large extent, task- and hand-specific. 相似文献
10.
Various devices have been developed to assess impairment of the autonomic nervous system, while other devices have been developed to evaluate the motor system. However, no devices have been developed to examine the interaction between the autonomic and somatic nervous systems. Therefore, the device described here, a square platform which was 0.7 × 0.7 m in length and 0.1 m thick, was developed to examine somatic-autonomic interaction. The device can be used by placing it directly on the floor or on 1 of 2 pivots; one that allowed the platform to move 0.2 m (±44.1°) in the front to back or side to side direction and one that allowed both movements together. Strain gauge load cells in the platform measured sway and tremor during the subjects attempt to balance and a continuous blood pressure monitor and the ECG were used to assess the response of the autonomic nervous system (heart rate variability). The device was tested on 5 normal subjects and the following was evaluated: (1) sway during standing, (2) weight shift during standing, (3) frequency of sway and extent of sway during standing, (4) sympathetic and parasympathetic alterations in the ANS during attempted balance, and (5) phase delays between motor and autonomic responses. The results showed that, with increasing balance challenge, sway increased, tremor increased, the sway angle increased and sway was positively correlated with heart rate and negatively correlated with blood pressure. A balance challenge significantly increased sympathetic activity but not parasympathetic activity. This device should have useful applications in assessing motor impairments and sensory and autonomic impairments in a variety of conditions. 相似文献
11.
N. Teasdale G. E. Stelmach A. Breunig H. J. Meeuwsen 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1991,85(3):691-696
Summary Numerous authors have reported that elderly persons are more affected than young adults when submitted to reduced or conflicting sensory inputs conditions. These results, however, do not permit to evaluate whether the elderly suffer from a reduced peripheral sensibility or from a deficit in the central integrative mechanisms responsible for configuring the postural set. The present experiment evaluated the ability of elderly to reconfigure the postural set when submitted to successive reduced and augmented visual sensory conditions. Results showed that young and elderly subjects' sway dispersion increased when they were exposed to a reduced visual sensory condition (i.e., vision/no-vision transition). However, when exposed to augmented sensory condition (i.e., no-vision/vision transitions) young adults were able to adapt rapidly and reduced their sway dispersion whereas the elderly exhibited an increased sway dispersion. This inability to adapt to an augmented sensory condition suggest that elderly persons, in addition to a reduced peripheral sensibility, have a deficit with central integrative mechanisms responsible for reconfiguring the postural set. 相似文献
12.
Stambolieva K Diafas V Bachev V Christova L Gatev P 《European journal of applied physiology》2012,112(5):1807-1815
We studied the postural stability of 23 canoeing and kayaking young athletes and 15 healthy untrained age matched subjects
during quiet and sensory conflicted stance (standing on stable and foam support with open and closed eyes). We measured with
a force platform the center of pressure excursions and applied mean sway amplitude (MA), mean sway velocity (SV) and their
Romberg ratios, and sway dispersion index to evaluate standing balance. During standing with eyes open, the athletes in comparison
to non-athletes showed in sagittal and frontal plane greater MA and SV when the support was stable and smaller MA and SV when
it was unstable. During standing with eyes closed, there were no differences between groups when the support was stable, however,
the athletes sway faster and have smaller MA than controls while standing on the foam support. During standing on stable support,
Romberg ratios for MA and SV revealed that unlike non-athletes the athletes’ MA and SV were vision independent. However, while
standing on unstable support the athletes’ MA and SV became vision dependent and even greater for the medio-lateral sway.
Canoeists’ SV vision dependency in both planes was greater than for other groups. These results are in line with our hypothesis
that young kayaking and canoeing athletes have a different from non-athletes model of sensory integration due to their specific
sporting activity. One possible mechanism of this model may be a subtle re-adaptation deficit after disembarking to stable
ground with diminished sensitivity of vision and vestibular apparatus. 相似文献
13.
K. Hüfner T. Stephan V.L. Flanagin A. Deutschlnder A. Stein R. Kalla T. Dera G. Fesl K. Jahn M. Strupp T. Brandt 《Neuroscience letters》2009,466(1):30-34
In functional brain imaging, specific task conditions can be compared to a reference condition which is often eyes-open or eyes-closed in darkness without the execution of a specific task. Previous fMRI studies in sighted subjects have shown that eyes-open in darkness, without visual stimulation, increases the relative activity in cortical ocular motor and attentional areas (“exteroceptive” state; contrast OPEN > CLOSED). By contrast, eyes-closed causes a relative signal increase in sensory systems (“interoceptive” state; contrast CLOSED > OPEN). In the present study we used fMRI to determine whether these differential brain activity states can also be found in congenitally blind subjects: there were intragroup differences between the OPEN and CLOSED conditions. These differences were, however, less pronounced and occurred in other areas than in sighted controls. The contrast OPEN > CLOSED revealed a relative signal increase in the left frontal eye field, the middle occipital gyrus bilaterally and in the anterior cingulum. Relative signal increases in occipital cortex areas and the anterior cingulum were also apparent for this contrast in the intergroup comparison (congenitally totally blind subjects vs. sighted controls). They reflect the increased attentional load or arousal during the eyes-open condition and could be indicative of a functional reorganization of the occipital cortex in the blind. The contrast CLOSED > OPEN in the congenitally totally blind subjects lead to relative activations in the somatosensory cortex bilaterally, the middle temporal gyrus on the left and the frontal gyri on the right. These activations are residues of the “interoceptive” state found in sighted controls. 相似文献
14.
Collignon O Voss P Lassonde M Lepore F 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2009,192(3):343-358
Until only a few decades ago, researchers still considered sensory cortices to be fixed or “hardwired,” with specific cortical
regions solely dedicated to the processing of selective sensory inputs. But recent evidences have shown that the brain can
rewire itself, showing an impressive range of cross-modal plasticity. Visual deprivation is one of the rare human models that
allow us to explore the role of experience-dependent plasticity of a sensory cortex deprived of its natural inputs. The objective
of this paper is to describe recent results regarding the spatial processing of sounds in blind subjects. These studies suggest
that blind individuals may demonstrate exceptional abilities in auditory spatial processing and that such enhanced performances
may be intrinsically linked to the recruitment of occipital areas deprived of their normal visual inputs. Such results highlight
the brain’s remarkable ability to rewire its components to compensate for the challenging neurological condition that is visual
deprivation. Moreover, we shall discuss that such cross-modal recruitment may, to some extent, follow organizational principles
similar to the functional topography of the region observed in the sighted. Even if such recruitment is especially present
in individuals having lost their sight in early infancy, occipital regions also show impressive plastic properties when vision
is lost at a later age. This observation will be related to recent results demonstrating that occipital regions play a more
important role than previously expected in the spatial processing of sounds, even in sighted subjects. Putative physiological
mechanisms underlying such cross-modal recruitment will then be discussed. All these results have important implications for
understanding the role of visual experience in shaping the development of occipital regions and may guide the implementation
of rehabilitative methods such as sensory substitution or neural implants.
相似文献
Franco Lepore (Corresponding author)Email: |
15.
Radhakrishnan SM Hatzitaki V Patikas D Amiridis IG 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2011,213(4):423-433
Achilles tendon vibration (ATV) alters proprioceptive input of the triceps surae muscles resulting in a posterior postural
shift during standing. When this is applied in combination with a more dynamic proprioceptive perturbation, postural responses
to ATV are attenuated. In this study, we applied ATV during self-paced, visually and auditory guided voluntary periodic sway
in order to examine how the vibration-induced afferent input is processed and reweighted at the presence of inter-sensory
guidance stimuli. Seventeen healthy adults (aged 26.7 ± 4.23 years) performed 15 cycles of periodic sway under three sensory
guidance conditions: (a) self-paced, (b) auditory paced (0.25 Hz), and (c) visually driven by matching the resultant force
vector to a target sine-wave (0.25 Hz). Bilateral ATV (80 Hz, 3 mm) was applied between the 5th and 10th sway cycles. ATV
evoked an earlier burst onset and increased activity of the plantarflexors consistent with a reduction in the amplitude and
duration of forward sway. This in turn resulted in an increase in dorsiflexors’ activity in order to compensate for the greater
backward sway. Postural responses to ATV were augmented when sway was auditory and visually guided. Forward sway variability
increased with ATV and remained high while backward sway variability decreased in the post-vibration phase. Our results suggest
that sensory context-dependent constraints that determine the degree of active control of posture and associated postural
challenge involved in a particular task determine how the vibration-induced Ia afferent input will be registered and further
processed by the central nervous system. 相似文献
16.
Suppression of visually evoked postural responses 总被引:5,自引:5,他引:0
Bronstein A. M. 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1986,63(3):655-658
Summary Normal subjects standing on an earth-fixed force platform inside a movable room displaced at velocities comparable to those accompanying spontaneous body sway, exhibit a visually evoked postural response (VEPR) some 600 ms after the start of the room movement. It consists of a displacement of the centre of force of the body in the direction of the stimulus (primary component), followed shortly by a corrective displacement in the opposite (secondary component). On second presentation of the stimulus VEPR is markedly reduced, but only if full proprioceptive information from the lower limbs is available to the subjects. A patient deprived of this information showed much enhanced VEPR which he was unable to suppress, in contrast to a patient with absent vestibular function who presented normal VEPR. The results show that in the presence of conflict between different sensory clues, vision is initially dominant in sway control, although adaptive processes can quickly rearrange this hierarchy. 相似文献
17.
Nagy E Feher-Kiss A Barnai M Domján-Preszner A Angyan L Horvath G 《European journal of applied physiology》2007,100(1):97-104
The changes in postural control in elderly people after an 8-week training course were characterized. Static postural stability
was measured during standing on a single force platform first with the eyes open and then with the eyes closed. Body sway
was analysed on a force plate in groups of elderly and of young subjects. Half of the elderly subjects then took part in the
training course. The posturographic measurements were repeated after the course. The sway in anteroposterior (AP) and mediolateral
(ML) directions was subjected to spectral analysis. The frequency spectrum of the platform oscillations was calculated by
fast Fourier transformation in the intervals 0.1–0.3, 0.3–1 and 1–3 Hz. It was found that the sway path was longer and the
frequency power was higher in the elderly group. The training caused a significant improvement in functional performance,
but a significantly longer sway path was observed after the training in the ML direction. The frequency analysis revealed
a significantly higher power after 8 weeks without visual control in the ML direction in the training group in the low and
the middle frequency bands. The results suggest that the participants’ balance confidence and the control of ML balance improved
in response to the training. The higher ML frequency power exhibited after the training may be indicative of a better balance
performance. Thus, the increase in the sway path in this age group did not mean a further impairment of the postural control. 相似文献
18.
Simoneau M Richer N Mercier P Allard P Teasdale N 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2006,170(4):576-582
Balance control is influenced by the availability and integrity of sensory inputs as well as the ability of the balance control mechanisms to tailor the corrective action to the gravitational torque. In this study, to challenge balance control, visual and ankle proprioceptive information were perturbed (eyes closed and/or tendon vibration). We masked sensory inputs in order: (1) to test the hypothesis that adolescent idiopathic scoliosis (AIS), compared to healthy adolescent, relies more on ankle proprioception and/or visual inputs to regulate balance and (2) to determine whether it is the variation or the amplitude of the balance control commands of AIS that leads to greater body sway oscillations during sensory deprivation. By manipulating the availability of the sensory inputs and measuring the outcomes, center of pressure (CP) range and velocity variability, we could objectively determine the cost of visual and/or ankle proprioception deprivation on balance control. The CP range was larger and the root mean square (RMS) of the CP velocity was more variable for AIS than for control participants when ankle proprioception was perturbed. This was observed regardless of whether vision was available or not. The analysis of the sway density curves revealed that the amplitude rather than the variation of the balance control commands was related to a larger CP range and greater RMS CP velocity for AIS. The present results suggest that AIS, compared to control participants, relies much more on ankle proprioception to control the amplitude of the balance control commands. 相似文献
19.
Julie A. E. Christensen Sbrina Aubin Tore Nielsen Maurice Ptito Ron Kupers Poul Jennum 《Journal of sleep research》2019,28(6)
There is ongoing controversy regarding the role of rapid eye movements (EMs) during rapid eye movement (REM) sleep. One prevailing hypothesis is that EMs during REM sleep are indicative of the presence of visual imagery in dreams. We tested the validity of this hypothesis by measuring EMs in blind subjects and correlating these with visual dream content. Eleven blind subjects, of whom five were congenitally blind (CB) and six late blind (LB), and 11 matched sighted control (SC) subjects participated in this study. All participants underwent full‐night polysomnography (PSG) recordings that were staged manually following American Academy of Sleep Medicine (AASM) criteria. Nocturnal EMs were detected automatically using a validated EM detector, and EM activity was represented as “EM coverage” computed as percentage of time with EM in each sleep stage. Frequency of sensory dream elements was measured in dream recall questionnaires over a 30‐day period. Both blind groups showed less EM coverage during wakefulness, N1, N2 and REM sleep than did controls. CB and LB subjects did not differ in EM activity. Validation of the detector applied to blind subjects revealed an overall accuracy of 95.6 ± 3.6%. Analysis of dream reports revealed that LB subjects reported significantly more visual dream elements than did CB. Although no specific mechanisms can be revealed in the current study, the quasi absence of nocturnal EMs in LB subjects despite preserved visual dream content does not support the visual scanning of dreams hypothesis. Specifically, results suggest a dissociation between EMs and visual dream content in blind individuals. 相似文献
20.
B. Amblard J. Crémieux A. R. Marchand A. Carblanc 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1985,61(1):21-37
Summary The differential contributions of static versus dynamic visual cues to postural control were studied in human subjects. Lateral body oscillations were measured with accelerometers located at head, hips and ankle levels, while subjects righted their balance under various mechanical conditions: i) on either a soft (foam rubber) support or a hard one, and ii) in either the classical or the sharpened Romberg stance. The visual pattern (horizontal or vertical rectangular grating) was illuminated with either a stroboscopic bulb or a normal one, and control measurements were also taken in darkness for each mechanical condition. Acceleration signals were processed into their frequency power spectra, the mean area and shape of which were taken to characterize the postural skills involved and the effects of either the visual suppressions or the mechanical destabilizations. Although dynamic visual cues have already been found to play a major role in the control of lateral body sway (Amblard and Crémieux 1976), we demonstrate here that static visual cues, the only ones available under stroboscopic illumination, also make a clear though minor contribution. Hence we suggest the existence of two modes of visual control of lateral balance in man, which are well separated in terms of the frequency range of body sway: the first mechanism, which operates below 2 Hz and is strobe-resistant, seems to control the orientation of the upper part of the body; the second mechanism, which operates above 4 Hz, centers on about 7 Hz and is strobe-vulnerable, seems to immobilize the body working upwards from the feet. Thus static visual cues may slowly control re-orientation or displacement, whereas dynamic visual cues may contribute to fast stabilization of the body. In between the frequency ranges at which these two visuomotor mechanisms come into play, at about 3 Hz, there is what we call a blind frequency, a visually neutral sway frequency which may arise from the incompatibility of visual reorientation with visual stabilization, and where vision appears unable to reduce postural sway to any marked extent. Transmission of the destabilization produced by suppression of visual cues or by mechanical methods from one anatomical level to another is also briefly discussed in terms of bio-mechanical constraints, and the correlations between various pairs of levels are considered. 相似文献