Kavli Affiliate: James Knierim
| Authors: William Hockeimer, Ruo-Yah Lai, Maanasa Natrajan, William Snider and James J. Knierim
| Summary:
The hippocampus is believed to encode episodic memory by binding information about the content of experience within a spatial framework encoding the location of that experience. Previous work implies a distinction between positional inputs to the hippocampus that provide information about an animal′s location and nonpositional inputs which provide information about the content of experience, both sensory and navigational. Here we leverage the phenomenon of “place field repetition” to better understand the functional dissociation between positional and nonpositional inputs to CA1 as rats navigated freely on a novel city-block maze, which combined elements of open-field foraging and linear-track tasks. Unlike typical results in open-field foraging, place fields were directionally tuned on the maze, even though the animal’s behavior was not constrained to 1-D trajectories. Repeating fields from the same cell tended to have the same directional preference when the fields were aligned along a linear corridor of the maze, but they showed uncorrelated directional preferences when they were unaligned across different corridors. Lastly, individual fields displayed complex time dynamics which resulted in the population activity changing gradually over the course of minutes. These temporal dynamics were evident across repeating fields of the same cell. These results demonstrate that the positional inputs that drive a cell to fire in similar locations across the maze can be behaviorally and temporally dissociated from the nonpositional inputs that alter the firing rates of the cell within its place fields, thereby increasing the flexibility of the system to encode episodic variables within a stable, spatial framework provided by place cells.