Medial temporal lobe roles in human path integration.

Naohide Yamamoto,Daniel A Gajewski,Anthony J Caputy,John W Philbeck,Joeanna C Arthur,Adam J Woods,Lucien Levy,Samuel J Potolicchio,Marc H E De Lussanet

doi:10.1371/journal.pone.0096583

Abstract

Path integration is a process in which observers derive their location by integrating self-motion signals along their locomotion trajectory. Although the medial temporal lobe (MTL) is thought to take part in path integration, the scope of its role for path integration remains unclear. To address this issue, we administered a variety of tasks involving path integration and other related processes to a group of neurosurgical patients whose MTL was unilaterally resected as therapy for epilepsy. These patients were unimpaired relative to neurologically intact controls in many tasks that required integration of various kinds of sensory self-motion information. However, the same patients (especially those who had lesions in the right hemisphere) walked farther than the controls when attempting to walk without vision to a previewed target. Importantly, this task was unique in our test battery in that it allowed participants to form a mental representation of the target location and anticipate their upcoming walking trajectory before they began moving. Thus, these results put forth a new idea that the role of MTL structures for human path integration may stem from their participation in predicting the consequences of one's locomotor actions. The strengths of this new theoretical viewpoint are discussed.

Highlights

An important function of vision is to facilitate navigation
logical memory (LM) I and II data were not obtained for one CONT participant, behavioral inattention test (BIT) data were not obtained for three LTLR and one RTLR participants, and spatial span data were not obtained for one LTLR participant
Pairwise contrasts for LM II showed that the LTLR group performed more poorly than the CONT and RTLR groups (p = .002 and .012, respectively), but that the CONT and RTLR groups did not differ from each other (p = .571)

Summary

Introduction

An important function of vision is to facilitate navigation. As important as this function is, visual information is frequently degraded or made unavailable by occlusions or poor lighting conditions. The average human can sight a target up to 20 m away or more, and walk to it accurately in an open field while blindfolded– responses tend to become more variable as the target distance increases, observers typically reach the target with very little systematic error [1,2]. This kind of non-visual navigation precludes using visible landmarks to determine one’s position, so the brain must rely upon internally generated (idiothetic) selfmotion information, such as vestibular and proprioceptive signals. Good performance in the blindfolded walking task indicates that the brain is finely tuned to sense and integrate the on-going selfmotion signals when walking along linear trajectories

Results

Discussion

Conclusion