The Relationship Between Road Sign Learning And Path Integration In Space Navigation Of Mice

Landmark learning refers to the process of analyzing and acquiring the landmark information. Path integration is the process that navigators keep updating the representations of their positions via integrating self-motion information(vestibular,proprioceptive, visual, etc.). Both landmark learning and path integration are key issues in the current spatial navigation research. Our study explored the relationships between landmark learning and path integration in mice. In particular, the following questions guided this study: 1) Whether, in normal spatial navigation, a navigator processes landmark learning and integrating self-motion information simultaneously? 2) Whether is it more efficient for the navigator to use both landmark information and self-motion information than using either information alone? and 3), What is the nature of the interaction between the two processes, i.e., whether landmark learning and path integration interfere with or enhance each other?The previous researches have shown that the gender of navigator and landmark types may affect the spatial navigation behavior. Therefore, this study chose the male mice to be the subjects and the beacon and associative clues which are easy-handling to be the landmark. In order to precise the research outputs, two types of water mazes were used:alley water maze and Morris water maze. Meanwhile, three experiments were designed to proof the hypothesis.Experiment 1 explored the relationships of landmark learning and path integration in alley water maze, where the type of landmark was beacon. By placing a landmark or not,adjusting the stability of platform to manipulate the manner of mice processing spatial information. For example, placing a landmark and changing the location of the platform to make mice’s path integration invalid, then mice could only use landmark(landmark group,LM); without placing landmark in the dark, then mice could only process self-motion information(path integration group, PI); placing a landmark and stabling its position with the platform, then mice had two kinds of information to process(landmark & path integration group, LP). Founds of experiment 1 are: 1) there were no significant differences between LP and LM, but both groups were more efficient significantly than PI in navigation performance. 2) LP’s test results of path integration were better than LM, but were worse than PI; LP’s test results of landmark learning were better than PI, but were worse than LM.Experiment 2 explored the relationships in alley water maze, where the type of landmark was associative cue. We used A string of small lights as associative cue. The experimental logic was the same as that in experimental 1. The results were concident withthat of experiment 1.Experiment 3 explored the relationships in Morris water maze. where the type of landmark was beacon. The experimental logic was the same as that in experimental 1.Founds are: 1) There were no significant differences between LP and LM, but both groups were more efficient significantly than PI in navigation performance. 2) LP’s test results of path integration had no significant difference with LM, but were worse than PI; LP’s test results of landmark learning were better than PI, but were not different significantly with LM.These results illustrated that: 1) In normal spatial navigation, mice processes landmark learning and integrating self-motion information simultaneously; 2) it’s more efficient for mice to use both landmark information and self-motion information or to use landmark information alone than using self-motion information alone, while, there is no difference between using two kinds of information and using landmark information alone. 3) path integration interferes landmark learning in alley water maze, whereas the later interferes the former in Morris water maze.This study resolved the debate on whether a navigator processes landmark learning and integrating self-motion information simultaneously in normal spatial navigation, and came to a comprehensive conclusion. What’s more, by comparing the effects of different spatial clues on navigation behaviors, in the basis, we proposed and proved that the interference is the nature interaction when we carry out the two processes. By the way, the alley water maze that we designed and the experimental method were proved efficient, so that it can be applied as a new paradigm in future reseaches.