The control of lower limb sensory inputs associated with a seated inverted-pendulum balancing task
This thesis is an investigation of the control of sensory inputs during the performance of inverted-pendulum balancing tasks. Three experiments were conducted to examine modulation of proprioceptive inputs during balance tasks of varying difficulty. It was hypothesized that (1) proprioceptive inputs to the cortex would be facilitated during a challenged balance task, (2) such facilitation would not be observed at the spinal level, (3) cortical facilitation would be unaffected by peripheral inhibitory influences, and (4) the availability of visual inputs would attenuate the facilitation of proprioceptive inputs. The hypotheses were supported by the data. It is concluded that there is task-specific re-weighting of sensory inputs to the cortex during challenged balance control. This re-weighting may depend on the availability of alternate sensory inputs. The increased transmission of proprioceptive inputs to the cortex and the decreased transmission at the spinal level suggest that the cortex plays an important role in challenged balance, whereas the role for the spinal (H) reflex appears to be less important.