Investigating the functional role of sensory receptors in human movement and postural control

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As humans, we use visual and vestibular (inner ear) information, as well as input from sensors in muscles and skin, to maintain balance. The long term objective of my research program is to understand the physiological mechanisms which enable information from the skin, muscles and vestibular system to modulate ongoing tasks and generate appropriate postural responses during standing and walking. My immediate goal is to investigate the mechanisms by which skin and vestibular information are able to contribute to balance during standing. Information from skin on the foot sole has been shown to have a role in postural stability. This can be demonstrated by an increase in sway with either anaesthesia or through cooling of the foot soles. There are different types of sensory receptors in the foot sole; they have been shown to alter muscle activity in the leg. This observation suggests a motor connection from skin for the control of lower limb movement, and perhaps balance control. By using the novel technique of microneurography, where recordings are made from single afferent nerve fibres in the human, we can isolate individual types of skin afferents. Correlating changes in sway to the activation of individual receptors will enable us to test the type of information from the skin that is important to maintain stability. Although input from the vestibular system has also been shown to change muscle activity in the legs, it is poorly understood how skin and vestibular input are integrated to control balance. My work will test how vestibular inputs interact with information from independent foot sole cutaneous receptors at the level of the spinal cord. This work is fundamental to understanding the mechanisms behind the cutaneous and vestibular involvement in balance and is a first step towards long term solutions for deficits in cutaneous input (such as diabetic neuropathy, age). Knowledge of the contributions from specific receptors, and their interaction with vestibular input will ultimately help streamline rehabilitative strategies and lead to improvements in our ability to aid individuals with mobility and balance deficits.