Between 1994 and 2003 spatial disorientation resulted in at least 202 aircraft accidents, 184 of them resulting in fatalities. Galvanic Vestibular Stimulation (GVS) provides a cost effective and safe way to simulate spatial disorientation and potentially test pilot’s vestibular system prior to aircraft operation. This experiment investigates the use of GVS as an indicator of motion sensitivity and explores the effects of GVS on flight simulation performance. Bilateral bipolar rectangular pulse electrical stimulations were given to subjects via skin-mounted electrodes placed over each mastoid process to stimulate the vestibular system with roll and yaw sensations. Two studies were conducted in this work: one on motion sensitivity and one to examine the effects of GVS during flight simulator use. The motion sensitivity test consisted of an alternating GVS sequence to simulate rolling back and forth. The sequence did generate motion sickness in two out of 12 subjects. Results show no correlation to motion history scores calculated from Kennedy’s Motion Sickness Questionnaire (MSQ). The flight simulator test coupled automatically generated congruent, conflicting, and sham orientation sensations to the roll angles of the aircraft. The stimulations used in this test did not indicate any effect on the simulator flight performance of the subjects. Feedback from subjects during this test raised concern over the delay between left- and right-side stimuli. Further testing to reduce the surface skin sensation showed that a ramp or increasing exponential waveform not only reduced the sensation of current entering the body but significantly increased the orientation sensations resulting from the stimulation. Increasing the orientation response and decreasing the sensation of current breaking the surface of the skin provides a much more desired stimulation for each of the tests in this experiment and any other future tests related to GVS.

The work presented in this thesis has two distinct parts: (i) development of a spinal motion measurement technique and (ii) incorporation of the spinal motion measurement with galvanic vestibular stimulation (GVS) technology, acting as a balance assist device hereafter referred to as a galvanic vestibular stimulation device (GVSD). The developed spinal motion measurement technique fulfills seven desired attributes: accuracy, portability, real-time data capture of dynamic data, non-invasive, small device footprint, clinically useful and of non-prohibitive cost. Applications of the proposed system range from diagnosis of spine injury to postural and balance monitoring, on-field as well as in the lab setting. The system is comprised of three inertial measurement sensors, respectively attached and calibrated to the head, torso and hips, based on the subject’s anatomical planes. Sensor output is transformed into meaningful clinical parameters of rotation, flexion-extension and lateral bending of each body segment with respect to a global reference space, then collected and visualized via an interactive graphical user interface (GUI). The accuracy of the proposed sensing system has been successfully verified with subject trials using a VICON optical motion measurement system. Next, the proposed motion measurement system and technique has been used to record a standing iv subject’s motion response to GVS. The data obtained allows the development of a new GVSD with the attributes of: eligibility for commercial licensing, portability, and capable of safely providing controlled stimulating current to the mastoid bones at varying levels and frequencies. The successful combination of the spinal motion measurement technique and GVSD represents the preliminary stage of a balance prosthesis.