Biology subjects

Royer, S.

Publications and source records attributed to Royer, S..

4 recordsLinked to original sources

bioRxiv2025

Grid cells encode reward distance during path integration in cue-rich environments

The medial entorhinal cortex supports both path integration and landmark anchoring, but how these computations interact during goal-directed navigation is unclear. We show that grid cells dissociate from landmarks and instead encode reward distance when mice perform a path integration task on a cue-rich treadmill. Grid cell population activity reset at rewards and shifted coherently across trials, consistent with continuous attractor dynamics realigned by rewards. Furthermore, grid cells exhibited reduced spatial scales, broadened theta frequency distributions, and altered temporal coordination. These phenomena were captured by a theta interference model incorporating cell competition and two sets of theta oscillating inputs whose frequencies shifted apart. Switching to cue-based navigation stabilized the firing fields and partially restored grid scale, theta frequencies and temporal structure. These results demonstrate that MEC circuits flexibly reset to encode goal-directed trajectories, and suggest that continuous attractor and interference mechanisms normally cooperate but can decouple under path integration demands.

neuroscience↗

bioRxiv2023

Stochastic characterization of navigation strategies in an automated variant of the Barnes maze

Animals can use a repertoire of strategies to navigate in an environment, and it remains an intriguing question how these strategies are selected based on the nature and familiarity of environments. To investigate this question, we developed a fully automated variant of the Barnes maze, characterized by 24 vestibules distributed along the periphery of a circular arena, and monitored the trajectories of mice over 15 days as they learned to navigate towards a goal vestibule from a random start vestibule. We show that the patterns of vestibule visits can be reproduced by the combination of three stochastic processes reminiscent of random, serial and spatial strategies. The processes randomly selected vestibules based on either uniform (random) or biased (serial and spatial) probability distributions. They closely matched experimental data across a range of statistical distributions characterizing the length, distribution, step size, direction, and stereotypy of vestibule sequences, revealing a shift from random to spatial and serial strategies over time, with a strategy switch occurring approximately every six vestibule visits. Our study provides a novel apparatus and analysis toolset for tracking the repertoire of navigation strategies and demonstrates that a set of stochastic processes can largely account for exploration patterns in the Barnes maze.

animal behavior and cognition↗

bioRxiv2020

Subcircuits of deep and superficial CA1 place cells support efficient spatial coding across heterogeneous environments

The hippocampus is thought to guide navigation by forming a cognitive map of space. However, the behavioral demands for such a map can vary depending on particular features of a given environment. For example, an environment rich in cues may require a finer resolution map than an open space. It is unclear how the hippocampal cognitive map adjusts to meet these distinct behavioral demands. To address this issue, we examined the spatial coding characteristics of hippocampal neurons in mice and rats navigating different environments. We found that CA1 place cells located in the superficial sublayer were more active in cue-poor environments, and preferentially used a firing rate code driven by intra-hippocampal inputs. In contrast, place cells located in the deep sublayer were more active in cue-rich environments and expressed a phase code driven by entorhinal inputs. Switching between these two spatial coding modes was supported by the interaction between excitatory gamma inputs and local inhibition.

neuroscience↗

bioRxiv2019

Place cell map genesis via competitive learning and conjunctive coding in the dentate gyrus

Place cells exhibit spatially selective firing fields and collectively map the continuum of positions in environments; how such network pattern develops with experience remains unclear. Here, we recorded putative granule (GC) and mossy (MC) cells from the dentate gyrus (DG) over 27 days as mice repetitively ran through a sequence of objects fixed onto a treadmill belt. We observed a progressive transformation of GC spatial representations, from a sparse encoding of object locations and periodic spatial intervals to increasingly more single, evenly dispersed place fields, while MCs showed little transformation and preferentially encoded object locations. A competitive learning model of the DG reproduced GC transformations via the progressive integration of landmark-vector cells and grid cell inputs and required MC-mediated feedforward inhibition to evenly distribute GC representations, suggesting that GCs progressively encode conjunctions of objects and spatial information via competitive learning, while MCs help homogenize GC spatial representations.

neuroscience↗