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Session: Prostheses
Session starts: Thursday 24 January, 13:30
Presentation starts: 14:45
Room: Lecture room 558

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Erwin Maaswinkel ()
DirkJan Veeger ()
Jaap van Dieën ()

Abstract:
Introduction: There is evidence that touch cues from any part of the body in contact with a stable external object may have a profound influence on the control of body orientation. The influence of touch has been illuminated specifically in studies of standing postural sway. However, to our knowledge, this work has not investigated the influence of touch feedback on the control of trunk posture. Therefore, the objective of the current study was to investigate the contribution of different sensory systems, in particular touch, to maintaining a seated upright posture. Methods: 13 subjects sat on a stool and were instructed to sit as still as possible. Trunk sway was measured with a motion capture system. During selected trials, a sensory perturbation was applied in the form of vibration of the paraspinal back muscles (90 Hz) or galvanic vestibular stimulation (GVS, 1.5 mA, 1 Hz). In addition, during some trials, subjects were allowed to maintain a very light contact (< 2 N) with the actuator of a force-controlled motor with either the index finger of the dominant hand or the back (T7). Results: Muscle vibration increased postural sway sharply. In contrast, GVS had no significant effect on seated postural sway. Touch feedback did not decrease sway in neutral conditions. However, touch through both the index finger and the back greatly reduced the effect of muscle vibration on postural sway. Conclusion: The results presented indicate that vestibular information either does not play a significant role in maintaining a seated upright posture or is easily compensated for when the system is challenged by GVS. In contrast, local information from muscle spindles appears to play an important role, as perturbing the spindles with muscle vibration resulted in a large increase of sway. Touch appears to play a unique role as the effects are only observed when local information from muscle spindles is perturbed. When no perturbations are applied, touch provides no additional benefit to controlling the trunk in a seated upright posture. These results support the notion that different sensory systems are integrated to control trunk posture and that the contribution of these systems can be reweighted. In particular, sensory reweighting between touch and muscle spindles seems to occur when muscle spindle information is perturbed. This research is supported by the Dutch Technology Foundation STW, which is part of the Netherlands Organisation for Scientific Research (NWO) and partly funded by the Ministry of Economic Affairs, Agriculture and Innovation. See www.neurosipe.nl - Project 10732: QDISC