Human subjects during upright stance show random postural oscillations which are controlled by central nervous system. The sensory feedback is based on information from the visual, vestibular, proprioceptive and cutaneous systems. A deficit in any of these sensory systems causes a loss in the performance of the postural control system, leading to increased amplitude of the postural oscillations, which is associated with a greater likelihood of falling. On the other hand, if there is an addition or amplification of sensory information in relation to those occurring naturally, there may be a significant improvement in posture control. An example of this effect occurs when the experimental subject lightly touches the fingertip ("light touch" or LT) on a surface fixed to the ground. This sensory (somestetic) cue is enough to reduce the amplitude of the postural oscillations during quiet stance. In a recent paper, we showed that if the supporting surface of the finger is stochastically vibrated, there is a further improvement as compared to LT. Such an improvement was attributed to the phenomenon resonance stochastic (RS) in sensory receptors. However, we need improve our knowledge on the mechanisms associated with LT, both in terms of sensory and motor aspects associated with the phenomenon. One of the objectives of the proposed research is to evaluate the degree of contribution of different populations of sensory receptors of the finger, hand, forearm and arm of the subject to the effect of LT. A question to be answered is whether a habituation effect of stochastic vibration of the contact surface occurs during SR. A second objective is to better understand the mechanisms of the improved motor performance during upright posture supplemented with LT. For example, we propose to investigate whether the main mechanism is associated with a stabilizing force generated by the plantar flexors, or wheter the main mechanism would be a minor wobble around the hip joint. Experimental approaches will merge tools and knowledge from Biomedical Engineering, neurophysiology and human biomechanics. There is potential applicability of the results to the clinical practice.
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