Navigating in a Virtual 3d-maze: Two Competitive Frames of References for Perceiving and Memorising

Although recent studies have brought new insights concerning the mechanisms of spatial memory and cognitive strategies during navigation, most of these studies have concerned 2D navigation and little is know concerning the problem of 3D spatial memory. In a previous experiment we have studied the influence of the relation between egocentric and allocentric frame of references on memorisation of complex 3D-structured environments in which one moved. These environments could represent buildings with several floors or a space station. In terrestrial navigation, self-motion includes yaw rotations and eventually vertical translations at vertical sections whereas in weightless navigation one can move along or turn about any axis. Results have shown that when only one mental rotation (the yaw) had to be performed to shift from egocentric to allocentric reference frame, memorisation of such corridors was improved. In a first experiment, we investigated if any single rotation axis is enough to facilitate this reference shift, and if not what in the terrestrial condition lead to better performances since three aligned axes could facilitate the reference shift (gravity, body and displacement’s rotation axes). We compared in a computerised 3D-reproduction of the maze task the four conditions defined by dissociating these axes. Field dependent (FD) and independent (FI) subjects as determined by the rod and frame test showed distinct effects of the navigation conditions. FD group performances strongly degraded when gravity and body axis were conflicting, independently of the rotation axis whereas FI subjects performances only slightly decreased when the body was tilted and the rotation axis aligned with gravity. Besides tilting the body in the control condition only deteriorated performances for FD group. A third experiment was sent on board of the International Space Station and three cosmonauts were involved in this study. Since gravity could provide the reference frame for the terrestrial condition, we wanted to check if the suppression of sensed gravity would change the relative performances of weightless and terrestrial condition. Results apparently indicate that the suppression of sensed gravity doesn’t affect at short term the performances of each condition, but could affect performances at long term in longer flights.