In this experiment, the authors studied subjects' capacity to determine the position of a fixed target after varying head-in-space positions. The subject sat on a chair positioned at the centre of a semicircular black cylinder. The chair could be rotated by the examiner about the vertical axis. Subjects were instructed to gaze at a straight-ahead target and then to indicate the perceived position of the target after head-trunk rotations. Subjects were found to be able to retrieve the position of the target when their head remained stationary: but when the subjects were rotated during active head rotations, their precision in target position estimation was markedly decreased. Overall, the results suggest that cervical signals are likely to be the source of information that allows accurate coding of target position after head rotations when the trunk remains stationary. The finding highlights the danger that a driver may encounter during non-instrumental navigation in the dark. (A)
Abstract