Asymmetrical influence of bi-thermal caloric vestibular stimulation on a temporal order judgment task.

Abstract

Recent evidences suggest that binaural vestibular stimulation affects tactile temporal processing. However, it remains difficult to determine the physiological mechanisms supporting the vestibular-somatosensory interactions observed during a TOJ task. Controlling the activation of the right or left vestibular system separately could allow to better understand the physiological bases of these findings and reconcile previous studies. The objective of the present study was to examine tactile temporal processing using a temporal order judgment task following selective stimulation of the right and left vestibular system with bi-thermal caloric vestibular stimulation (CVS). A total of 24 right-handed participants received bi-thermal CVS either in the right ear (n = 12) or the left ear (n = 12). Participants held vibrators in both hands which delivered a signal temporally separated by a variable asynchrony. Participants had to report the hand where the vibration was perceived first. The task was performed in three different CVS conditions: (1) baseline, (2) warm CVS, and (3) cold CVS. Analysis of the logistics curve parameters-just noticeable difference (JND) and point of subjective simultaneity (PSS)-for each participant in each CVS conditions revealed an increase in JND greater following warm CVS. A significant increase in JND following warm CVS was measured bilaterally. However, cold CVS increased JND only when CVS was applied in the left ear, but not in the right ear. Finally, no influence of CVS on PSS was observed.