Characterizing a cortical cell-type-specific signal for navigational errors

Abstract Spatial navigation requires the coordination of neural activity across many areas in the brain to integrate sensory, motor, and cognitive information. Through its interconnections with many of these areas, the retrosplenial cortex plays an important role in navigation by representing key aspects of the environment, sustaining memories, and translating between different perspectives in space. Many of these studies report the activity of individual neurons and lesioning of the entire area to evaluate function. However, it remains unclear which molecularly defined cell types within the area contribute to its function for navigation. This lack of investigation into cell types for navigation is notable given the repeated circuit motifs and distinct roles of cell types discovered throughout cortex for other functions. Our lab has identified a specific cell type, called Sst44 cells, in the posterior parietal cortex, an adjacent cortical area also involved in navigation, where its activity corresponds to corrections of navigational errors. I will build on this work to determine the role of Sst44 cells in retrosplenial cortex in mice during goal- directed navigation. My preliminary results suggest the activity of Sst44 cells in retrosplenial cortex may respond to a different aspect of navigational errors. Whereas the posterior parietal cortex has a privileged role in actions and egocentric processing of navigational information, the retrosplenial cortex contributes to the transformation of related signals to allocentric representations. Here, I propose two approaches to systematically determine the cell type’s function. In Aim 1, I will design virtual reality navigation tasks to quantify the activity of Sst44 cells in RSC in relation to egocentric and allocentric errors. In Aim 2, I will inhibit the activity of Sst44 cells to evaluate how the loss of their function impacts navigation and representation of spatial information in other cell types. Addressing these aims will bring unique precision in our understanding of a cell type’s contribution to navigation.