Master of Science (MSc)
Faculty of Science
Dr. Michael Cinelli
Background: The vestibular system has been shown to contribute to mechanisms of locomotion such as distance perception. Galvanic vestibular stimulation (GVS) is a tool used to perturb the vestibular system, and causes significant deviations in path trajectory during locomotion. Previous research has suggested that applying GVS during straight-line locomotion tasks is not sufficient to determine the effects of the vestibular system on locomotion. However, spatial navigation challenges one’s ability to navigate throughout the environment using idiothetic cues to constantly update one’s position. The purpose of the current study was to determine the effects of GVS on both path trajectory and body rotation during a task of spatial navigation in the absence of visual cues, and how accuracy of this task is affected by dance training. It was hypothesized that the delivery of GVS would significantly increase errors during the triangle completion task, and this increase would be more pronounced in the control participants compared to the dancers.
Methods: Participants (n=34, all female, 18-30 years) were divided into two groups: controls (n=18) had no experience with sport-specific training while dancers (n=16) had previously experienced dance training (M = 15.6 years, SD = ±4.1) and were still currently training in dance (M = 11.5 hours/week, SD = ±7.3). Monofilament testing (Touch-Test Six Piece Foot Kit) was used to determine the plantar surface cutaneous sensitivity threshold and a joint angle-matching task was used to quantify the proprioceptive awareness of each individual. Participants completed trials of the triangle completion task in VR (via Oculus Rift DK2), during which they would navigate along the first two legs of one of two triangles using visual input, and then accurately navigate back to their initial position with the use of vision. GVS was delivered at three times the participant’s threshold in either the left or right direction prior to the final body rotation and until the participant reached their end position. The task was completed six times for each of the GVS conditions (with and without GVS) with the experimental GVS condition being further divided into right and left perturbation trials, for each of the two triangles, in both the right and left triangle directions, for a total of 48 trials (six trials x 2 GVS conditions x 2 triangles x 2 directions). Whole body kinematic data were collected at 60 Hz using an NDI Optotrak motion tracking system.
Results: No significant differences were observed between control subjects and dancers with respect to arrival error, angular error, path variability, cutaneous sensitivity or proprioceptive awareness. However, there was a significant effect of GVS on both arrival error and angular error. Conditions without GVS had significantly smaller angular error than both conditions with GVS. In addition, GVS conditions with the perturbation in the same direction as the final body rotation had significantly greater arrival error than both the condition without GVS and with the current in the opposite direction of the final body rotation. There was no significant difference between GVS conditions in path variability during the return to the initial position.
Conclusions: The significant effect of GVS on both arrival error and angular rotation demonstrates that vestibular perturbation reduced the accuracy of the triangle completion task. These findings suggest that the vestibular system plays a major role in both path trajectory and body rotation during tasks of spatial navigation in the absence of vision.
Karn, Tanya, "The effect of GVS on path trajectory and body rotation in the absence of visual cues during a spatial navigation task" (2015). Theses and Dissertations (Comprehensive). 1779.