The Mechanisms of Path Integration in Humans

102 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007.Path integration refers to the ability to integrate self-motion information to estimate one's current position and orientation relative to the origin. We used a homing task in virtual hallway-mazes to investigate the mechanisms of path integration in humans. First, we examined spatial updating in path integration in Experiments 1 and 2. Participants traveled along random five-segment paths, either with or without distinctive landmarks at segment intersections. When they arrived at the end of the paths, they were instructed to directly return to the origin or one of the landmarks. Consequently, they showed worse homing performance in the landmark-present trials than in the landmark-absent trials. The influences of landmarks on the path completion task and the simple direction response task were compared. The results suggest that the presence of task-relevant landmarks introduced updating costs to path integration, which supports that spatial updating in path integration is egocentric. Second, we investigated the mechanism of path integration errors by examining the effects of path complexity and path configuration on homing performance in Experiments 3 and 4. In contrast to the classical hypothesis that path integration is subject to encoding error accumulation, our results suggest that path completion errors cannot be explained by the encoding errors alone and alternative models are needed. Last, we examined the effects of active selection of the outbound paths in path integration. Participants traveled along hallways and attempted to directly return to the origin upon seeing a golden apple. Half participants decided the direction and distance of each hallway by themselves, either freely (in Experiment 5) or on a forced-choice basis (in Experiment 6). In contrast, the other half subjects followed the identical outbound paths selected by their counterparts. Thus, the two groups received the same perceptual and motor information but differed in the voluntary selection of the path structure. Although the results from both experiments suggest no facilitation effects of active selection on overall homing performance, active selection of the outbound paths influenced estimations of homing distances. The role of path integration in human navigation was discussed.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD