Without vestibular input, humans tend to become visually dependent and construct perceptions of upright from visual clues. The risk for spatial disorientation is substantial in altered states of gravity, which may cause both acute and chronic issues. Non-invasive vestibular prosthetics offer a promising approach to this matter. Galvanic vestibular stimulation (GVS) involves placing electrodes on the mastoid process and activating central vestibular areas directly. However, the efficacy of this method is highly inconsistent between individuals. This project aims to construct an automated calibration process for the GVS, allowing the wearer to receive enhanced vestibular input without causing disorientation. As the GVS activates the vestibular system, the eyes will reflexively move through the vestibulo-ocular reflex (VOR). The eye position will be recorded through an eye-tracker and fed-back into a microcontroller powering the GVS. The relative intensity of either side can then be automatically adjusted until no eye-movements are recorded and vestibular equilibrium has been achieved, which will also be ascertained through physiological and psychomotor tests. In order to ascertain that prolonged use of the GVS does not negatively impact the central nervous system, animal trials will be performed using the lamprey. This vertebrate possesses a well-developed vestibular system, which we will stimulate through the use of electrodes and vibrating coins in both ex-vivo and chronic in-vivo trials. This will allow us to perform both electrophysiological and anatomical studies on the brainstem. This project approaches a number of key questions relating to vestibular perceptions in altered states of gravity, aiming to enhance gravitational information in a safe and consistent manner. The protocols may also offer an important platform for future studies in the field and yield valuable insights into the use of GVS systems.
