Investigating a method to determine the anterior-posterior extent of the rat Posterior Parietal Cortex

Abstract

This paper investigates a methodology to define the anterior-posterior (AP) borders of the posterior parietal cortex (PPC) in the rat brain. This region receives incoming connections from neurons in other brain regions. The regions directly anterior and posterior to PPC also receive incoming connections but from different brain regions. We injected two different retrograde tracers, which travel backwards along neurons, into volumes in and around the PPC, along a line parallel to the AP axis. If the two tracers move to very different brain regions, then the injection sites were probably not both in the same region. This would indicate that a border lies somewhere in between the two injection sites. We provide preliminary results from two rats, qualitatively showing examples of a pair of injection sites straddling a border and a pair of injection sites within the same region. We then describe both the advantages of the techniques we used and the aspects of our methods that should be improved. We hope to provide a roadmap for future experimenters interested in investigating this problem.