Effect of navigation direction on the dual-task of counting backward during blind navigation

Blind navigation towards a remembered target is associated with large direction errors when executed with a side stepping walking pattern. To investigate whether sideways navigation requires higher attention resource than forward navigation, a dual-task paradigm of backward counting during blind navigation was used. The objectives were to determine the effect of this dual-task on navigation errors, gait velocity and the rate of backward counting and to establish whether this effect is larger during sideways than forward navigation. A group of 17 subjects participated. The primary task was to navigate without vision towards previously seen targets located on the floor 8 m away in four directions (ahead, behind, to the right or left) and to stop at the place the target was presumed to be. Forward, backward and side stepping gait patterns were used to reach corresponding targets. The secondary task was to count backwards in steps of three. The dual-task was to perform blind navigation while counting backwards. The rate of backward counting was significantly decreased in the dual-task relative to a controlled sitting condition (p < 0.05), but this reduction was similar among navigation directions. Navigation errors were not changed between navigation only and dual-task. Gait velocity was significantly slower in the dual-task than in navigation only (p < 0.05). This suggests that counting backward while navigating without vision towards a remembered target exceeded the subjects' attention capacity. However, sideways navigation did not seem to require more attention than forward navigation, even though navigation was much less precise in sideways than forward navigation.