The vestibular system provides vital information about head position and motion; which is used for the control of balance through vestibulospinal reflexes. Chapter 2 explores the process of transforming head position to body coordinates, with and without vision. The results show when vision is available, the evoked response is less precise. Chapter 3 explores the transformation process before and after 60 days of bedrest. After this period of inactivity, participants swayed more, and their EVS-evoked sway response was less precise. This decrement in precision appears to begin recovery 6 days postbedrest.
Chapter 4 focuses on vestibulo-ocular reflexes rather than postural reflexes. Electrical vestibular stimulation is used to evoke measurable torsional eye-movements. The magnitude of the response is modulated by stimulus frequency. Results suggest that CNS interprets electrical vestibular stimulation as a velocity signal rather than a position or acceleration signal. This technique is an ideal measure of pure vestibular function, Chapter 5 utilised the technique in a clinical environment. Vestibular schwannoma patients, with known unilateral vestibular deficit, were tested to identify if the proposed technique can detect this deficit. Results showed that asymmetries could be detected, and, the test may be more sensitive than previously used measures of vestibular asymmetries