Trading Place for Space: Increasing Location Resolution Reduces Contextual Capacity in Hippocampal Codes

Area of Science:

• Neuroscience
• Cognitive Science
• Computational Neuroscience

Background:

• Animals form cognitive maps using place cells in the hippocampus.
• Place cell remapping explains how the brain represents different contexts.
• Previous research focused on the physiological basis of remapping, not its contextual capacity.

Purpose of the Study:

• To quantify how place cell firing properties influence the hippocampus's contextual capacity.
• To develop a geometric model for analyzing population-level place cell activity.
• To investigate the relationship between place cell firing properties and representational geometry.

Main Methods:

• A geometric approach was used to model population activity of place cells.
• Analysis focused on how changes in place cell firing properties affect representational distances in firing rate space.
• Calculations were performed using known firing field statistics.

Main Results:

• Hippocampal contextual capacity grows exponentially with the number of place cells.
• A trade-off exists between positional encoding resolution and the number of storable contexts.
• Place cell width influences this trade-off, potentially explaining dorsal-ventral axis variations.

Conclusions:

• The geometric framework provides a method to calculate the hippocampus's contextual capacity.
• Place cell clustering near boundaries enhances contextual capacity.
• The model can be extended to include other cell types and abstract representations.