Organization of hippocampal CA3 into correlated cell assemblies supports a stable spatial code

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Computational Neuroscience

Background:

• The CA3 subfield of the hippocampus is hypothesized to stably store memories via recurrently connected cell assemblies.
• Understanding the unique coding properties of CA3 and their role in memory stability and neural code precision is crucial.

Purpose of the Study:

• To investigate the collective coding properties of hippocampal CA3 and CA1 subfields in freely behaving mice.
• To determine how these properties contribute to the stability and precision of the neural code for memory storage.

Main Methods:

• Large-scale calcium (Ca2+) imaging was employed in hippocampal CA1 and CA3.
• Mice repeatedly explored novel environments over several weeks.
• Analysis focused on place cell tuning precision, stability, and peer dependence.

Main Results:

• CA3 place cells exhibited more precise and stable tuning compared to CA1 place cells.
• CA3 cells demonstrated higher statistical dependence on their peers, indicating cell assembly organization.
• While tuning precision and long-term stability were correlated, peer dependence was linked to higher stability but not necessarily higher precision.

Conclusions:

• A three-way relationship exists between tuning precision, long-term stability, and peer dependence in the hippocampus.
• Cellular assembly organization in CA3 appears to underlie the long-term storage of information.
• These findings provide insights into the neural mechanisms of stable memory formation.