Mapping the anterior-posterior extent of the rat posterior parietal cortex and its shared inputs with the frontal orienting fields

Abstract

In mammals, the posterior parietal cortex (PPC) is part of an elaborate neural network crucial for directed spatial attention, learning, and decision-making. In rats, investigation of the PPC’s role in these neural mechanisms is complicated by inconsistencies in its location in the cortex. To address this issue, we injected Alexa Fluor-conjugated cholera toxin subunit B (CTB), an anterograde and retrograde axonal tracer, into regions within and around the PPC along the anterior-posterior axis. Using anatomical definitions based on thalamic connectivity, we have preliminarily mapped out the A-P extent of the PPC to between -3.5mm and -4.5mm relative to bregma, considerably more posterior than currently accepted values. Using these updated estimations of the PPC's location, we found candidates for the site of evidence accumulation in decision making within neural network underlying directed spatial attention and decision-making, believed to project to both the PPC and the frontal orienting fields (FOF). Regions containing significant afferent connectivity to both FOF and PPC were flagged and analyzed for viability as targets of future investigation.