Abstract
Although it is widely accepted that visual and vestibular (mainly otolith) systems affect tilt perception, the contribution of somatosensory system to the tilt perception is still unclear. To investigate the influence of somatosensory inputs from lower limb on the tilt perception, subjective visual vertical (SVV) and head stability were measured during upright standing on the platform tilted to the right (0, 3, 6 and 9 degrees) under the dark in five healthy subjects (22-32 years) for over 3 minutes. The values of SVV (between -1.5 and 3.5 degrees) and the head tilt (between -2.5 and 3.5 degrees) were small and they had almost no relationship to the platform tilt: the correlation coefficients were 0.15 (p>0.18) and 0.13 (p>0.21), respectively. On the other hand, the correlation coefficients between the SVV value and the head tilt at 0, 3, 6 and 9 degrees of platform tilt were -0.17 (p>0.32), 0.06 (p>0.50), 0.53 (p>0.10) and 0.75 (p<0.02), respectively. These results indicate that the SVV (=the tilt perception) is determined by the combination of the platform tilt (=the somatosensory inputs from lower limb) and the head tilt (=the vestibular and/or the neck somatosensory inputs). [J Physiol Sci. 2007;57 Suppl:S110]
