Human movement science
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Human movement science · Apr 2011
Updating process of internal model of action as assessed from motor and postural strategies in young adults.
Internal models are constantly updated based on the actions and experiences of a person in the world. In the present study, we proposed to assess the updating process of internal models of action by providing new environmental constraints for motor planning, postural control, and execution processes in daily tasks such as STS and BTS. STS and BTS tasks were performed with different inclinations of the support surface on which the participant and the chair were positioned: horizontal support, support tilted 10° to the right, or forward. ⋯ Concerning the movement analysis our results showed (1) temporal asymmetry between STS and BTS, attributed mainly to the integration of the mechanical effects of gravity, and (2) a decrease of trunk movements when the support was tilted forward, attesting to an immediate adaptation process. Concerning the postural analysis our study revealed that adults adopted selective head stabilization on space strategy with respect to balance constraints. To conclude, young adults were able to immediately update their internal model of action in order to optimize motor control and vertical body orientation.
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Human movement science · Apr 2011
Self-motion perception and vestibulo-ocular reflex during whole body yaw rotation in standing subjects: the role of head position and neck proprioception.
Self-motion perception and vestibulo-ocular reflex (VOR) were studied during whole body yaw rotation in the dark at different static head positions. Rotations consisted of four cycles of symmetric sinusoidal and asymmetric oscillations. Self-motion perception was evaluated by measuring the ability of subjects to manually track a static remembered target. ⋯ Further, vibration (100 Hz) of the neck muscles splenius capitis and sternocleidomastoideus remarkably influenced perceived rotation during asymmetric oscillation. On the other hand, SPEP of VOR was modulated by active head deviation, but was not influenced by neck muscle vibration. Through its effects on motion perception and reflex gain, head position improved gaze stability and enhanced self-motion perception in the direction of the head deviation.
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Human movement science · Apr 2011
Proprioceptive impairment and postural orientation control in Parkinson's disease.
Impairment of postural control is a common consequence of Parkinson's disease (PD). Increasing evidences demonstrate that the pathophysiology of postural disorders in PD includes deficits in proprioceptive processing and integration. However, the nature of these deficits has not been thoroughly examined. ⋯ In the second experiment, the postural reactions of the PP were similar to those of the CS at the beginning of the perturbation and increased drastically at the end of the perturbation's period as compared to those of CS and could induce fall. These results will bring new concepts to the sensorimotor postural control, to the physiopathology of posture, equilibrium and falls in PD and to the role of basal ganglia pathways in proprioception integration. Nevertheless, in order to assess precisely the role played by sensorimotor integration deficits in postural impairments in PD, further studies establishing the links between clinical features and abnormalities are now required.