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Updated: Aug 6, 2026
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Investigating Long-term Synaptic Plasticity in Interlamellar Hippocampus CA1 by Electrophysiological Field Recording
Published on: August 11, 2019
Hippocampal engrams configure prefrontal context representations to guide flexible decisions
Joshua B Julian1, Jesse C Kaminsky1, David W Tank1
1Princeton Neuroscience Institute, Princeton, NJ, USA.
Biorxiv : the Preprint Server for Biology
|July 17, 2026
Summary
Hippocampal engrams, which store memories, can flexibly guide behavior by reactivating context representations in the medial prefrontal cortex (mPFC). This memory reactivation enables rule-based decision-making, not just fixed responses.
Area of Science:
- Neuroscience
- Cognitive Neuroscience
- Systems Neuroscience
Background:
- Flexible behavior relies on configuring neural computations with past experiences.
- Hippocampal (HPC) engrams are known to drive learned behaviors, but their role in retrieving multiple stimulus-response mappings is unclear.
- How engrams influence cortical representations and dynamics to produce context-dependent behavior remains uninvestigated.
Purpose of the Study:
- To determine if HPC engrams can retrieve sets of stimulus-response mappings, not just single responses.
- To investigate how HPC engrams affect cortical task representations and dynamics.
- To establish a neural mechanism for how memory traces control flexible, context-dependent behavior.
Main Methods:
- Combined engram tagging and reactivation in the HPC with large-scale neural recordings in the medial prefrontal cortex (mPFC) of mice.
- Utilized a context-dependent task-switching paradigm to assess behavioral flexibility.
- Analyzed neural dynamics in mPFC during HPC engram reactivation.
Main Results:
- Reactivation of HPC engrams induced engram-consistent decision-rules, demonstrating retrieval of behavioral strategies.
- HPC engram reactivation rapidly reinstated context representations in the mPFC within milliseconds.
- This neural reconfiguration in mPFC led to context-appropriate choices, while other mPFC dynamics remained largely unaffected.
Conclusions:
- HPC engrams causally drive flexible behavior by configuring downstream cortical circuits in real-time.
- Engrams can retrieve and implement sets of decision rules, supporting complex cognitive flexibility.
- This study reveals a neural mechanism linking memory engrams to adaptive, context-dependent behavior through rapid cortical state modulation.
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