Discipline: Biological Sciences
Subcategory: Physiology and Health
Jordan Dreher - Norfolk State University
Co-Author(s): Andrew Alexander, Boston University, MA; Lucas Carstensen, Boston University, MA; Michael Hasselmo, Boston University, MA
The retrosplenial cortex (RSC) is an association area that is highly interconnected with sensory and motor processing regions as well as structures that are known to represent an animal’s position or heading direction with respect to the external environment. Neural spatial representations have primarily been studied while animals freely forage in a large open arena. In contrast, RSC spatial responses have, with a few exceptions, been primarily examined while the animal performs track running tasks. Given that RSC serves as both an input and output center for broader neural spatial circuitry, it is important to examine RSC spatial responses in two-dimensional environments. The purpose of the experiment was to further characterize RSC spatial representations during free exploration. To do so, in vivo electrophysiological recordings were performed while rats explored familiar and novel arenas that had varying shapes or visual cue configurations. To perform these recordings, a 16-tetrode hyperdrive was manufactured and implanted into the rat’s brain. It was determined that a sub-population of RSC neurons exhibited activity that was tuned to the egocentric relationship of the animal with respect to environmental boundaries. This may have important implications for goal-directed navigation. Pilot injections, that express genetically-encoded calcium indicators, were completed to enable one photon imaging of these neurons, Egocentric Boundary Cells, in RSC and dorsal striatum. This imaging will enable recordings of more neurons simultaneously to elucidate their role in more complex spatial tasks. References: Seralynne D. Vann*, John P. Aggleton* and Eleanor A. Maguire‡. (2009) What does the retrosplenial cortex do? 10(792-802) James R. Hinman, Holger Dannenberg, Andrew S. Alexander, and Michael E. Hasselmo (2018). Neural mechanisms of navigation involving interactions of cortical and subcortical structures. (2007-2029) Cho, J., & Sharp, P. E. (2001). Head direction, place, and movement correlates for cells in the rat retrosplenial cortex. Behavioral neuroscience, 115(1), 3. Alexander, A. S., & Nitz, D. A. (2015). Retrosplenial cortex maps the conjunction of internal and external spaces. Nature neuroscience, 18(8), 1143. O’Keefe, J., & Dostrovsky, J. (1971). The hippocampus as a spatial map: Preliminary evidence from unit activity in the freely-moving rat. Brain research. Hafting, T., Fyhn, M., Molden, S., Moser, M. B., & Moser, E. I. (2005). Microstructure of a spatial map in the entorhinal cortex. Nature, 436(7052), 801. Chen, Tsai-Wen, et al. “Ultrasensitive fluorescent proteins for imaging neuronal activity.” Nature 499.7458 (2013): 295.
Funder Acknowledgement(s): Funding provided by the National Science Foundation. I thank Helen Fawcett, Co-Director of the National Science Foundation Research Experience for Undergraduates in Integrated Nanomanufacturing and the Hasselmo Lab.
Faculty Advisor: Andrew Alexander, email@example.com
Role: I assisted in manufacturing two, 16 tetrode hyperdrives, observed the implantation of the drives, and assisted with the electrophysiological recordings. I also performed histology to image the cells within the brain tissue.