Investigator: Victoria Templer, Providence College

Mentor: Rebecca Burwell, Brown

Scientific Theme: Neuroscience

Abstract: The purpose of this project is to determine the functional contribution of the rat posterior parietal cortex (PPC) to specific forms of information processing and memory. Recent evidence suggests the primate dorsal PPC (dPPC) is involved in top-down attention and may be guiding behavior based on intention while the ventral/cadual (cPPC) is involved in bottom-up attention (Shomstein, 2012), that may reflect less highly- processed stimulus salience. While the primate and rat PPC is likely largely conserved across species, it is not known if such a functional differentiation is also found in the rat PPC. This gap in knowledge is further expanded by the lack of consensus of what brain coordinates should constitute the rat PPC. To our knowledge, rat electrophysiological and experimental lesion studies target only the dorsal portion of the PPC, ignoring the caudal limb (Swanson, 1992). Critically, however, it is the cPPC that is more closely connected with visual and spatial processing regions, including the postrhinal cortex (Agster & Burwell, 2009; Burwell & Amaral, 1998). As part of Specific Aim 1 we plan to first lesion the entire PPC to better localize this inclusive structure and determine the functional contribution to cognitive tasks that require both top-down processing and bottom-up processing. As part of Specific Aim 2, we will then employ a cross-lesion approach of the dorsal and caudal portions of the PPC to further demarcate bottom-up and top-down functions, including object in location memory and social cognition. Given unpublished electrophysiological data from Dr.Burwell’s laboratory, and our survey of the literature, the hypothesis is that the rat dPPC is biased toward top-down attention and the cPPC is biased toward salience-based, stimulus-guided responses. Additional experiments that employ cutting edge optogenetic and chemogenetic techniques will be employed that further address the contributions of the dPPC and cPPC to object in location memory and social cognition.

Human Health Relevance: Findings will have translational health relevance due to the PPC’s significant role in memory and corresponding dysfunction as a result of several forms of dementia and deterioration from old age. Progress in disease prevention and treatment of dementias depends on localization of the specific brain structures and cognitive processes responsible for distorted information and memory processing.