Vestibular Sensitivity and Vection Chronometry along the Spinal Axis in Erect Man

A study is reported of the relations between vestibular sensitivity and vection chronometry in healthy human adults. Twenty-three subjects were examined. For both vestibular and vection investigations, the subjects were seated in an armchair with the spinal axis aligned with the earth vertical and the head normally erect. The subjects' vestibular thresholds for detection of vertical upward accelerations were assessed by a double-staircase psychophysical method. The subjects' vection onset latencies were measured for both upward and downward directions. Since the vection onset latencies are presumed to be shortened by the decrease of the conflict between visual and vestibular afferents, the less-vestibular-sensitive subjects were hypothesised to have shorter vection onset latencies than the more-vestibular-sensitive ones. As expected, the results indicate a negative correlation between vestibular thresholds and vection onset latencies: the higher the vestibular thresholds, the lower the vection onset latencies.