Neural adaptations to age-related changes in vestibular hair cell function

The vestibular system is a set of inertial motion sensors within the inner ear, crucial for controlling balance and eye movements. People who damage this system experience instability and blurred vision. The vestibular apparatus works by transducing head motion into neural signals through hair cells which are mechanically deformed by movement. These cells are very similar to those involved in hearing and, just like auditory hair cells, vestibular hair cells are progressively lost as part of the normal ageing process. This partly explains the increased fall risk and poor vision as we age. However, this loss of function is less than would be expected from the extent of hair cell death. This suggests an adaptive neural mechanism exists which partially compensates for age-related vestibular loss.

In this project we will investigate this compensatory mechanism with the use of Galvanic Vestibular Stimulation (GVS). GVS is a non-invasive technique for stimulating the vestibular nerve with direct current. It evokes behavioural reflexes such as sway responses and eye movements, both of which can be measured in our laboratory. Since GVS bypasses the vestibular apparatus, it informs us about the neural gain of the vestibular-motor system, independent of hair cell function. By comparing older adults’ responses to natural vestibular stimuli (e.g. chair rotation) with those to GVS, we will estimate the extent of neural compensation to hair cell loss. This can then be related to broad measures of function such as postural stability and vision.

The project will involve the use of motion capture and eye movement recording in human volunteers exposed to vestibular stimulation. Analysis will involve system identification techniques in both time and frequency domains using Matlab.

Feel free to contact Dr Reynolds for further information.
http://www.birmingham.ac.uk/staff/profiles/sportex/reynolds-raymond.aspx
https://warwick.ac.uk/fac/cross_fac/mibtp/pgstudy/phd_opportunities/neuroscience2018/neuraladaptations