The intermediate hippocampus integrates shock-observation and spatial information during observational fear memory in male rats.

Intermediate hippocampus pyramidal neurons show enriched shock-excited activity and selectively stabilize shock-context spatial representations during observational fear memory in male rats.

• Why it matters: Observational fear requires mapping another’s distress onto the observer’s spatial representation, but the hippocampal mechanism for this integration and consolidation is unknown.
• What they did: Using Neuropixels recordings across dorsal, intermediate, and ventral hippocampus during contextual fear learning by observation, rest, and recall, the study measured shock-observation recruitment, place-field scaling, and post-learning sharp-wave ripple reactivation.
• The result: Shock-observation responses scaled with baseline place-field firing in dorsal and intermediate hippocampus, while intermediate hippocampus preferentially reactivated shock-context ensembles during sharp-wave ripples, especially in animals expressing contextual freezing.