Tactile cueing vs. vestibular sensation and nystagmus during yaw rotation

Introduction: It has been reported that vibrating electromechanical tactile stimulation on the torso overrides the vestibular sensation of rotation. The purpose of this study is to further examine the influence of tactile cues on real and apparent sensations of self-rotation and corresponding vestibular nystagmus during passive yaw rotation. Method: There were 15 healthy subjects (12 men and 3 women, 31 to 49 yr) who were subjected to clockwise yaw rotation at a constant velocity of 120 degrees center dot s(-1). A tactile vest using electromechanical tactors (8 columns x 3 rows) was activated either in the clockwise or counterclockwise direction in a randomized design. The sequential activation of the tactors around the body matched the velocity of chair rotation. Eye movements were monitored using infrared eye tracking. Since it is difficult to control for mental set (alertness and imagined target distance) during eye tracking, in addition to paying attention to the apparent sensation of self-motion, the sensation of rotation and the induced vestibular nystagmus were investigated separately. Results. ANOVA failed to reveal any significant effect. Our results suggested that tactile cueing did not enhance or suppress the subjective sensation of rotation during actual rotation, nor did it enhance or suppress the false sensation of rotation experienced. Also, tactile cueing had no effect on the gain and time constant of the induced per-rotation and post-rotation nystagmus with repeated exposures. Conclusion: It appears that tactile cueing delivered by a tactile garment provides a sense of direction, but it does not affect any concomitant vestibular responses.