1,721,069 research outputs found
Human Walking along a Curved Path. I. Body Trajectory, Segment Orientation, and the Effect of Vision.
No full textTask-related characteristics of gait and segment orientation during natural locomotion along a curved path have been described in order to gain insight into the neural organization of walking. The locomotor task implied continuous deviation from straight-ahead, thereby requiring continuous adjustment of body movement to produce and assist turn-related torques. Performance was compared to straight-ahead locomotion. Subjects easily reproduced both trajectories with eyes open (EO). The actual-to-required trajectory difference increased blindfolded (BF), more so during turning. Stride length was unchanged for the outer but decreased for the inner leg. The feet anticipated subsequent body rotation by pivoting toward the inner side of the curve at heel strike. A shift of body centre of mass and trunk roll toward the inner side accompanied turning. The head turned more than dictated by the heading change, and the absolute range of yaw oscillation increased. Head yaw anticipated body yaw by approximately 200 ms. Despite the minor effect of vision on the behaviour of all other segments, a difference in head pitch occurred between EO and BF; with EO, the head was flexed (P < 0.01), as to look at the path, while pitch was negligible with BF. In general, the changes in the amplitude of head, trunk and feet movements proved to be well related to the kinematics of the steering body, and constituted a sort of basic library of motor synergies
Neck muscle vibration and spatial orientation during stepping in humans
No full textUnilateral long-lasting vibration was applied to the sternomastoid muscle to assess the influence of asymmetric neck proprioceptive input on body
orientation during stepping-in-place. Blindfolded subjects performed 3 sequences of 3 trials, each lasting 60 s: control, vibration applied during stepping (VDS), and vibration applied before stepping (VBS). VDS
caused clear-cut whole body rotation toward the side opposite to vibration. The body rotated around a vertical axis placed at about arm’s length from the body. The rotation did not begin immediately on switching on
the vibrator. The delay varied from subject to subject from a few seconds to about 10 s. Once initiated, the angular velocity of rotation was remarkably constant (about 1°/s). In VBS, at the beginning of stepping, subjects rotated for a while as if their neck were still vibrated. At a variable delay,
the direction of rotation reversed, and the effects were opposite to those observed during VDS. Under no condition did head rotation, head roll, or lateral body tilt accompany rotation. The results confirm and extend the notion that the neck proprioceptive input plays a major role in body
orientation during locomotion. The body rotation does not seem to depend on the same mechanisms that modify the erect posture; rather, the asymmetric neck input would seem to modify the egocentric bodycentered coordinate system
Coordinated modulation of locomotor muscle synergies constructs straight-ahead and curvilinear walking in humans.
No full textWe describe the muscle synergies accompanying
steering of walking along curved trajectories, in order
to analyze the simultaneous control of progression
and balance-threatening emerging forces. For this purpose,
we bilaterally recorded in ten subjects the electromyograms
(EMGs) of a representative sample of leg
and trunk muscles (n=16) during continuous walking
along one straight and two curved trajectories at natural
speed. Curvilinear locomotion involved a graded, limbdependent
modulation of amplitude and timing of
activity of the muscles of the legs and trunk. The turnrelated
modulation of the motor pattern was highly
coordinated amongst muscles and body sides. For all
muscles, linear relationships were detected between the
spatial and temporal features of muscle EMG activity.
The largest modulation of EMG was observed in gastrocnemius
medialis and lateralis muscles, which showed
opposite changes in timing and amplitude during curvewalking.
Moreover, amplitude and timing characteristics
of muscle activities were significantly correlated with the
spatial and temporal gait adaptations that are associated
with curvilinear locomotion. The present results reveal
that fine-modulation of the muscle synergies underlying
straight-ahead locomotion is enough to generate the
adequate propulsive forces to steer walking and maintain
balance. These findings suggest that the turn-related
command operates by modulation of the phase relationships
between the tightly coupled neuronal assemblies
that drive motor neuron activity during walking.
This would produce the invariant templates for locomotion
kinematics that are at the base of human navigation
in space
Compte-rendu de lecture : A. Corbin, J.-J. Courtine, G. Vigarello (dir.), Histoire des émotions, vol. 1 et 2
No full textCompte-rendu de lecture : A. Corbin, J.-J. Courtine, G. Vigarello (dir.), Histoire des émotions, Paris, Seuil, 2016, vol. 1 et 2 par S. Broomhall, à consulter sur le site de H-France (décembre 2017
Personalized Neuroprosthetics
Full text linkDecades of technological developments have populated the field of neuroprosthetics with myriad replacement strategies, neuromodulation therapies, and rehabilitation procedures to improve the quality of life for individuals with neuromotor disorders. Despite the few but impressive clinical successes, and multiple breakthroughs in animal models, neuroprosthetic technologies remain mainly confined to sophisticated laboratory environments. We summarize the core principles and latest achievements in neuroprosthetics, but also address the challenges that lie along the path toward clinical fruition. We propose a pragmatic framework to personalise neurotechnologies and rehabilitation for patient-specific impairments to achieve the timely dissemination of neuroprosthetic medicine.UPCOURTINECNBITNECN
Penser les émotions à l’ombre des humanités classiques : A. Corbin, J.-J. Courtine, G. Vigarello (éds), Histoire des Émotions, vol. 1, De l’Antiquité aux Lumières, 2016
No full textSerghidou Anastasia. Penser les émotions à l’ombre des humanités classiques : A. Corbin, J.-J. Courtine, G. Vigarello (éds), Histoire des Émotions, vol. 1, De l’Antiquité aux Lumières, 2016. In: Dialogues d'histoire ancienne, vol. 44, n°1, 2018. pp. 313-325
Continuous leg muscle vibration is not detrimental to human walk.
No full textSensory feedback from the moving limbs contributes to the regulation of animal and human locomotion. However, the question of the specific role of the various modalities is still open. Further, functional loss of leg afferent fibres due to peripheral neuropathy does not always lead to major alteration in the gait pattern. In order to gain further insight on proprioceptive control of human gait, we applied vibratory tendon stimulation, known to recruit spindle primary afferent fibres, to both triceps surae muscles during normal floor walk. This procedure would disturb organisation and execution of walking, especially if spindles fire continuously and subjects are blindfolded. Vibration induced significant, though minor, changes in duration and length of stance and swing phase, and on speed of walking and kinematics of lower limb segments. No effect was induced on angular displacement of the ankle joint or trunk and
head kinematics. This paucity of effects was at variance with the perception of the subjects, who reported illusion of leg stiffness and gait imbalance. These findings would speak for a selective gating of Ia input during locomotion and emphasise the notion that the central nervous system can cope with an unusual continuous input along the Ia fibres from a key muscle like the soleus
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