Investigating the role of tactile feedback during balance and walking: stimuli, neural responses, and perception

The foot soles are the primary interface between humans and the external environment, conveying information about the environment we are standing and walking upon, and contributing to balance maintenance. However, little is known about the precise role of tactile feedback in balance and gait or what feedback during such behaviours looks like. This thesis tackles this issue by first characterising pressure distributions experienced by the foot sole, investigating neural responses to forces reflective of those experienced during gait, and finally establishing a link with perception. Using pressure sensitive insoles, Chapter 2 investigates the complexity of stimuli experienced by the foot sole during everyday behaviours including standing, walking on different surfaces and at different speeds, jogging and jumping. Results revealed spatially complex foot-surface interactions, suggesting rich tactile feedback on top of the wide ranging pressures experienced. Chapter 3 utilises a combination of experimental data and computational simulations to investigate tactile responses during gait to investigate cutaneous responses to naturalistic stimulation. Finally, tactile perception at the foot sole, including under high forces, is compared to the hand in Chapter 4. The results show that interaction type (low vs high force) influences perception more than body region, but remains highly correlated across body regions. Taken together, this thesis provides new-found insight into the breadth of stimuli experienced by the foot, shining light on the under-researched spatial component of stimuli. Furthermore, the tactile system is able to continue to respond under high forces, conveying vital information regarding the contact dynamics and the surfaces we are upon. In summary, the tactile system provides essential information during dynamic, high load behaviours that can aid in maintaining one's stability during gait.