Head tilt response: A complementary test to the Subjective Visual Vertical

This paper studies the phenomenon of the perceived vertical by means of a novel dynamic experiment. This task is inspired in the Subjective Visual Vertical test and can be regarded as complementary in terms of how the information involved varies (visual, otolithic and neck proprioception). The experiment consists in presenting a white stripe in a pair of virtual reality goggles and adjusting the roll angle of the head until the stripe is aligned with the gravitational vertical. The roll angle of the head is measured and recorded along each trial where the white stripe changes position four times, after a specific amount of time. The task was run on a group of 28 normal subjects and a small sample of 5 patients with vestibular hypofunction. Six parameters derived from Control Theory were extracted from the data to characterize the subject transient response. All parameters for normal subjects were found to be normally distributed. Experimental results show that discrimination is possible between normal subjects and patients using just one or two of the parameters studied.