Measuring Self-Motion Perception : Induced by Galvanic Vestibular Stimulation Captured by Voluntary Hand Movement

Sammanfattning

Self-motion involves the perception and awareness of one's own movement through three-dimensional space and is important for maintaining balance and spatial orientation. Self-motion sensations can be triggered using Galvanic Vestibular Stimulation (GVS), which stimulates the vestibular system, resulting in sensations of motion. Current research shows limitations in assessing perceived self-motion induced by GVS, relying on complex setups that are hard to replicate. This project develops a methodology to quantify perceived self-motion and provides a replicable setup for future research. The primary aim of this project was to develop and validate a methodology which allows us to objectively quantify perceived self-motion induced by GVS. The secondary goal was to investigate any correlation between GVS intensity and the velocity of perceived self-motion. To achieve these aims, the first step included translating the perceived self-motion into a voluntary hand movement, reflecting the perceived self-motion. The second step consisted of measuring the velocity of the hand movement, representing the velocity of perceived self-motion, by using two systems: an Inertial Measurement Unit (IMU) and a Motion Tracking Camera System (MTCS). These two systems were then used to compare and validate each other’s results. The study applied direct current (DC) intensities ranging from two to six mA with electrodes placed on the mastoid bones in a bipolar bilateral configuration to assess perceived self-motion. The developed methodology was used in a pilot trial to investigate any correlation between GVS current intensity and perceived self-motion velocity. Six healthy participants joined the trial, one of whom withdrew due to discomfort caused by GVS. When the velocity data was averaged across all subjects, the data suggested an underlying trend between GVS intensity and hand velocity. While there was considerable individual variability in hand velocity, a trend towards a moderate correlation between current intensity and hand velocity was observed, but this correlation could not be concluded with statistical significance. The developed methodology successfully compared and validated the results with both measurement systems. Even though the calculated difference between the two systems was considered small, a noticeable discrepancy remained evident. Due to drift and bias present in the IMU data, the MTCS was concluded to be more suitable for measuring hand-motion.