At least two main cognitive strategies can be used to solve a complex navigation task: the allocentric or map-based strategy and the sequential egocentric or route-based strategy. The sequential egocentric strategy differs from a succession of independent simple egocentric responses as it requires a sequential ordering of events, possibly sharing functional similarity with episodic memory in this regard. To question the possible simultaneous encoding of sequential egocentric and allocentric strategies, we developed a paradigm in which these two strategies are spontaneously used or imposed. Our results evidenced that sequential egocentric strategy can be spontaneously acquired at the onset of the training as well as allocentric strategy. Allocentric and sequential egocentric strategies could be used together within a trial, and bidirectional shifts (between trials) were spontaneously performed during the training period by 30% of the participants. Regardless of the strategy used spontaneously during the training, all participants could execute immediate shifts to the opposite non previously used strategy when this strategy was imposed. Altogether, our findings suggest that subjects acquire different types of spatial knowledge in parallel, namely knowledge permitting allocentric navigation as well as knowledge permitting sequential egocentric navigation.

None of the previous studies on aging have tested the influence of action with respect to the degree of interaction with the environment (active or passive navigation) and the source of itinerary choice (self or externally imposed), on episodic memory (EM) encoding. The aim of this pilot study was to explore the influence of these factors on feature binding (the association between what, where, and when) in EM and on the subjective sense of remembering. Navigation in a virtual city was performed by 64 young and 64 older adults in one of four modes of exploration: (1) passive condition where participants were immersed as passengers of a virtual car [no interaction, no itinerary control (IC)], (2) IC (the subject chose the itinerary, but did not drive the car), (3) low, or (4) high navigation control (the subject just moved the car on rails or drove the car with a steering-wheel and a gas pedal on a fixed itinerary, respectively). The task was to memorize as many events encountered in the virtual environment as possible along with their factual (what), spatial (where), and temporal (when) details, and then to perform immediate and delayed memory tests. An age-related decline was evidenced for immediate and delayed feature binding. Compared to passive and high navigation conditions, and regardless of age-groups, feature binding was enhanced by low navigation and IC conditions. The subjective sense of remembering was boosted by the IC in older adults. Memory performance following high navigation was specifically linked to variability in executive functions. The present findings suggest that the decision of the itinerary is beneficial to boost EM in aging, although it does not eliminate age-related deficits. Active navigation can also enhance EM when it is not too demanding for subjects’ cognitive resources.

During locomotion, a top-down organization has been previously demonstrated with the head as a stabilized platform and gaze anticipating the horizontal direction of the trajectory. However, the quantitative assessment of the anticipatory sequence from gaze to trajectory and body segments has not been documented. The present paper provides a detailed investigation into the spatial and temporal anticipatory relationships among the direction of gaze and body segments during locomotion. Participants had to walk along several mentally simulated complex trajectories, without any visual cues indicating the trajectory to follow. The trajectory shapes were presented to the participants on a sheet of paper. Our study includes an analysis of the relationships between horizontal gaze anticipatory behavior direction and the upcoming changes in the trajectory. Our findings confirm the following: 1) The hierarchical ordered organization of gaze and body segment orientations during complex trajectories and free locomotion. Gaze direction anticipates the head orientation, and head orientation anticipates reorientation of the other body segments. 2) The influence of the curvature of the trajectory and constraints of the tasks on the temporal and spatial relationships between gaze and the body segments: Increased curvature resulted in increased time and spatial anticipation. 3) A different sequence of gaze movements at inflection points where gaze plans a much later segment of the trajectory.