Possible uses of path integration in animal navigation

Path integration, in its simplest form, keeps track of movement from a star ting point and so makes it possible to return to this point. Path integrati on can also be used to build a metric spatial representation of the environ ment, if given a suitable readout mechanism that can store and recall the c oordinates of any one of multiple locations. A simple averaging process can make this representation as accurate as desired, given enough visits to th e locations stored in the representation. There are more than these two way s of using path integration in navigation. They can be classified systemati cally according to the following three criteria: Is there one point at whic h coordinates can be reset to correct errors, or several? Is there one poss ible goal, or several? Is there one path integrator, or several? I describe the resulting eight methods of using path integration and compare their ch aracteristics with the available experimental evidence. The classification offers a theoretical framework for further research.