Effects of 10 min tilt and visual directional information on ocular counterrolling

The effects of 10 min of static tilt on ocular counterrolling (OCR) were investigated. Seven healthy volunteers were tilted 45 degrees around the naso-occipital axis, fixed at that position for 10 min, and the pre- and post-tilt OCRs were recorded. OCR was video-recorded using an infrared CCD camera and subjected to computer image analysis. The subjects were directed to fixate on an imagined target in the dark (experiment 1), or viewed an earth vertical, striped pattern placed in front of his/her eyes to enhance the recognition of extent of body tilt (experiment 2). In experiment 1, the average OCRs recorded before and after 10 min of tilt showed no significant changes. However, in experiment 2, OCR decreased significantly after 10 min of tilt. These results suggest that visual perception of spatial verticality can produce time-dependent adaptation of OCR.