779 research outputs found
Sensory supplementation system based on electrotactile tongue biofeedback of head position for balance control
The present study aimed at investigating the effects of an artificial head
position-based tongue-placed electrotactile biofeedback on postural control
during quiet standing under different somatosensory conditions from the support
surface. Eight young healthy adults were asked to stand as immobile as possible
with their eyes closed on two Firm and Foam support surface conditions executed
in two conditions of No-biofeedback and Biofeedback. In the Foam condition, a
6-cm thick foam support surface was placed under the subjects' feet to alter
the quality and/or quantity of somatosensory information at the plantar sole
and the ankle. The underlying principle of the biofeedback consisted of
providing supplementary information about the head orientation with respect to
gravitational vertical through electrical stimulation of the tongue. Centre of
foot pressure (CoP) displacements were recorded using a force platform. Larger
CoP displacements were observed in the Foam than Firm conditions in the two
conditions of No-biofeedback and Biofeedback. Interestingly, this destabilizing
effect was less accentuated in the Biofeedback than No-biofeedback condition.
In accordance with the sensory re-weighting hypothesis for balance control, the
present findings evidence that the availability of the central nervous system
to integrate an artificial head orientation information delivered through
electrical stimulation of the tongue to limit the postural perturbation induced
by alteration of somatosensory input from the support surface
Muscle fatigue degrades force sense at the ankle joint
To investigate the effects of muscle fatigue on force sense at the ankle
joint, 10 young healthy adults were asked to perform an isometric
contra-lateral force ankle-matching task in two experimental conditions of: (1)
no-fatigue and (2) fatigue of the plantar-flexor muscles. Measures of the
overall accuracy and the variability of the force matching performances were
determined using the absolute error and the variable error, respectively.
Results showed less accurate and less consistent force matching performances in
the fatigue than no fatigue condition, as indicated by decreased absolute and
variable errors, respectively. The present findings evidence that muscle
fatigue degrades force sense at the ankle joint
Re-weighting of somatosensory inputs from the foot and the ankle for controlling posture during quiet standing following trunk extensor muscles fatigue
The present study focused on the effects of trunk extensor muscles fatigue on
postural control during quiet standing under different somatosensory conditions
from the foot and the ankle. With this aim, 20 young healthy adults were asked
to stand as immobile as possible in two conditions of No fatigue and Fatigue of
trunk extensor muscles. In Experiment 1 (n = 10), somatosensation from the foot
and the ankle was degraded by standing on a foam surface. In Experiment 2 (n =
10), somatosensation from the foot and ankle was facilitated through the
increased cutaneous feedback at the foot and ankle provided by strips of
athletic tape applied across both ankle joints. The centre of foot pressure
displacements (CoP) were recorded using a force platform. The results showed
that (1) trunk extensor muscles fatigue increased CoP displacements under
normal somatosensatory conditions (Experiment 1 and Experiment 2), (2) this
destabilizing effect was exacerbated when somatosensation from the foot and the
ankle was degraded (Experiment 1), and (3) this destabilizing effect was
mitigated when somatosensation from the foot and the ankle was facilitated
(Experiment 2). Altogether, the present findings evidenced re-weighting of
sensory cues for controlling posture during quiet standing following trunk
extensor muscles fatigue by increasing the reliance on the somatosensory inputs
from the foot and the ankle. This could have implications in clinical and
rehabilitative areas
Differential postural effects of plantar-flexor muscles fatigue under normal, altered and improved vestibular and neck somatosensory conditions
The aim of the present study was to assess the effects of plantar-flexor
muscles fatigue on postural control during quiet standing under normal, altered
and improved vestibular and neck somatosensory conditions. To address this
objective, young male university students were asked to stand upright as still
as possible with their eyes closed in two conditions of No Fatigue and Fatigue
of the plantar-flexor muscles. In Experiment 1 (n=15), the postural task was
executed in two Neutral head and Head tilted backward postures, recognized to
degrade vestibular and neck somatosensory information. In Experiment 2 (n=15),
the postural task was executed in two conditions of No tactile and Tactile
stimulation of the neck provided by the application of strips of adhesive
bandage to the skin over and around the neck. Centre of foot pressure
displacements were recorded using a force platform. Results showed that (1) the
Fatigue condition yielded increased CoP displacements relative to the No
Fatigue condition (Experiment 1 and Experiment 2), (2) this destabilizing
effect was more accentuated in the Head tilted backward posture than Neutral
head posture (Experiment 1) and (3) this destabilizing effect was less
accentuated in the condition of Tactile stimulation than that of No tactile
stimulation of the neck (Experiment 2). In the context of the multisensory
control of balance, these results suggest an increased reliance on vestibular
and neck somatosensory information for controlling posture during quiet
standing in condition of altered ankle neuromuscular function
The magnitude of the effect of calf muscles fatigue on postural control during bipedal quiet standing with vision depends on the eye-visual target distance
The purpose of the present experiment was to investigate whether, with
vision, the magnitude of the effect of calf muscles fatigue on postural control
during bipedal quiet standing depends on the eye-visual target distance. Twelve
young university students were asked to stand upright as immobile as possible
in three visual conditions (No vision, Vision 1m and Vision 4m) executed in two
conditions of No fatigue and Fatigue of the calf muscles. Centre of foot
pressure displacements were recorded using a force platform. Similar increased
variances of the centre of foot pressure displacements were observed in the
fatigue relative to the No fatigue condition for both the No vision and Vision
4m conditions. Interestingly, in the vision 1m condition, fatigue yielded: (1)
a similar increased variance of the centre of foot pressure displacements to
those observed in the No vision and Vision 4m conditions along the
medio-lateral axis and (2) a weaker destabilising effect relative to the No
vision and Vision 4m conditions along the antero-posterior axis. These results
evidence that the ability to use visual information for postural control during
bipedal quiet standing following calf muscles fatigue is dependent on the
eye-visual target distance. More largely, in the context of the multisensory
control of balance, the present findings suggest that the efficiency of the
sensory reweighting of visual sensory cues as the neuro-muscular constraints
acting on the subject change is critically linked with the quality of the
information the visual system obtains
Can a Plantar Pressure-Based Tongue-Placed Electrotactile Biofeedback Improve Postural Control Under Altered Vestibular and Neck Proprioceptive Conditions?
We investigated the effects of a plantar pressure-based tongue-placed
electrotactile biofeedback on postural control during quiet standing under
normal and altered vestibular and neck proprioceptive conditions. To achieve
this goal, fourteen young healthy adults were asked to stand upright as
immobile as possible with their eyes closed in two Neutral and Extended head
postures and two conditions of No-biofeedback and Biofeedback. The underlying
principle of the biofeedback consisted of providing supplementary information
related to foot sole pressure distribution through a wireless embedded
tongue-placed tactile output device. Centre of foot pressure (CoP)
displacements were recorded using a plantar pressure data acquisition system.
Results showed that (1) the Extended head posture yielded increased CoP
displacements relative to the Neutral head posture in the No-biofeedback
condition, with a greater effect along the anteroposterior than mediolateral
axis, whereas (2) no significant difference between the two Neutral and
Extended head postures was observed in the Biofeedback condition. The present
findings suggested that the availability of the plantar pressure-based
tongue-placed electrotactile biofeedback allowed the subjects to suppress the
destabilizing effect induced by the disruption of vestibular and neck
proprioceptive inputs associated with the head extended posture. These results
are discussed according to the sensory re-weighting hypothesis, whereby the
central nervous system would dynamically and selectively adjust the relative
contributions of sensory inputs (i.e., the sensory weights) to maintain upright
stance depending on the sensory contexts and the neuromuscular constraints
acting on the subject
Inter-individual variability in sensory weighting of a plantar pressure-based, tongue-placed tactile biofeedback for controlling posture
The purpose of the present experiment was to investigate whether the sensory
weighting of a plantar pressure-based, tongue-placed tactile biofeedback for
controlling posture could be subject to inter-individual variability. To
achieve this goal, 60 young healthy adults were asked to stand as immobile as
possible with their eyes closed in two conditions of No-biofeedback and
Biofeedback. Centre of foot pressure (CoP) displacements were recorded using a
force platform. Overall, results showed reduced CoP displacements in the
Biofeedback relative to the No-biofeedback condition, evidencing the ability of
the central nervous system to efficiently integrate an artificial
plantar-based, tongue-placed tactile biofeedback for controlling posture during
quiet standing. Results further showed a significant positive correlation
between the CoP displacements measured in the No-biofeedback condition and the
decrease in the CoP displacements induced by the use of the biofeedback. In
other words, the degree of postural stabilization appeared to depend on each
subject's balance control capabilities, the biofeedback yielding a greater
stabilizing effect in subjects exhibiting the largest CoP displacements when
standing in the No-biofeedback condition. On the whole, by evidencing a
significant inter-individual variability in sensory weighting of an additional
tactile information related to foot sole pressure distribution for controlling
posture, the present findings underscore the need and the necessity to address
the issue of inter-individual variability in the field of neuroscience
Tongue-placed tactile biofeedback suppresses the deleterious effects of muscle fatigue on joint position sense at the ankle
Whereas the acuity of the position sense at the ankle can be disturbed by
muscle fatigue, it recently also has been shown to be improved, under normal
ankle neuromuscular state, through the use of an artificial tongue-placed
tactile biofeedback. The underlying principle of this biofeedback consisted of
supplying individuals with supplementary information about the position of
their matching ankle position relative to their reference ankle position
through electrotactile stimulation of the tongue. Within this context, the
purpose of the present experiment was to investigate whether this biofeedback
could mitigate the deleterious effect of muscle fatigue on joint position sense
at the ankle. To address this objective, sixteen young healthy university
students were asked to perform an active ankle-matching task in two conditions
of No-fatigue and Fatigue of the ankle muscles and two conditions of
No-biofeedback and Biofeedback. Measures of the overall accuracy and the
variability of the positioning were determined using the absolute error and the
variable error, respectively. Results showed that the availability of the
biofeedback allowed the subjects to suppress the deleterious effects of muscle
fatigue on joint position sense at the ankle. In the context of sensory
re-weighting process, these findings suggested that the central nervous system
was able to integrate and increase the relative contribution of the artificial
tongue-placed tactile biofeedback to compensate for a proprioceptive
degradation at the ankle
A Wireless Embedded Tongue Tactile Biofeedback System for Balance Control
We describe the architecture of an original biofeedback system for balance
improvement for fall prevention and present results of a feasibility study. The
underlying principle of this biofeedback consists of providing supplementary
information related to foot sole pressure distribution through a wireless
embedded tongue-placed tactile output device. Twelve young healthy adults
voluntarily participated in this experiment. They were asked to stand as
immobile as possible with their eyes closed in two conditions of nobiofeedback
and biofeedback. Centre of foot pressure (CoP) displacements were recorded
using a force platform. Results showed reduced CoP displacements in the
biofeedback relative to the no-biofeedback condition. On the whole, the present
findings evidence the effectiveness of this system in improving postural
control on young healthy adults. Further investigations are needed to
strengthen the potential clinical value of this device.Comment: Pervasive and Mobile Computing (2008) in pres
Optimizing the Use of an Artificial Tongue-Placed Tactile Biofeedback for Improving Ankle Joint Position Sense in Humans
The performance of an artificial tongue-placed tactile biofeedback device for
improving ankle joint position sense was assessed in 12 young healthy adults
using an active matching task. The underlying principle of this system consists
of supplying individuals with supplementary information about the position of
the matching ankle relative to the reference ankle position through a
tongue-placed tactile output device generating electrotactile stimulation on a
36-point (6 X 6) matrix held against the surface of the tongue dorsum.
Precisely, (1) no electrodes were activated when both ankles were in a similar
angular position within a predetermined "angular dead zone" (ADZ); (2) 12
electrodes (2 X 6) of the anterior and posterior zones of the matrix were
activated (corresponding to the stimulation of the front and rear portion of
the tongue) when the matching ankle was in a too plantarflexed and dorsiflexed
position relative to the reference ankle, respectively. Two ADZ values of 0.5
degrees and 1.5 degrees were evaluated. Results showed (1) more accurate and
more consistent matching performances with than without biofeedback and (2)
more accurate and more consistent ankle joint matching performances when using
the biofeedback device with the smaller ADZ valu
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