September 23, 2026
Along with his team, Dr. Mark Brandon, a researcher at the Douglas Research Centre and Associate Professor in Psychiatry at McGill University, has just published an article investigating the brain networks involved in recalling fear memories.
Key take-aways
A study led by Dr. Mark Brandon (Douglas Resarch Centre / McGill Psychiatry) and colleagues challenges a long-held view of how the hippocampus stores and retrieves fear memories. Traditional theories suggest that the hippocampus keeps similar experiences separate to prevent confusion. Instead, the researchers found that after fear learning, the ventral hippocampus (vCA1) makes representations of threatening and neutral environments more similar, not less. This overlap appears to help the brain retrieve fear memories more quickly when danger is encountered.
Why this matters
Fear memories are critical for survival because they allow us to recognize and respond rapidly to threats. However, exaggerated or persistent fear responses are central to conditions such as PTSD and anxiety disorders. These findings suggest that, in threatening situations, the brain may prioritize speed over precision, offering a new perspective on how emotional memories are retrieved and why fear can sometimes become maladaptive.
What they did
The researchers developed an innovative “context teleportation” system that allowed mice to switch instantly between a fear-associated environment and a neutral environment while remaining in the same physical location. One environment was paired with mild footshocks and the other remained safe. Using miniscope calcium imaging, the team recorded activity from large populations of neurons in both the dorsal hippocampus (dCA1) and ventral hippocampus (vCA1) as mice learned and retrieved fear memories. They then examined how neural representations changed and how those changes related to fear-related freezing behaviour.
What they found
Fear conditioning changed neural representations in both hippocampal regions, but the effect was much stronger in vCA1. During memory retrieval, dCA1 maintained relatively distinct representations of threatening and neutral contexts. In contrast, vCA1 showed substantial overlap between the two. Despite this overlap, mice could still reliably distinguish safe from threatening environments. Importantly, vCA1 retrieved threat-related representations faster and more strongly than dCA1, and the dominance of the threat representation closely predicted fear behaviour.
What it means
The results reveal a previously unrecognized coding strategy in the ventral hippocampus. Rather than maximizing discrimination, vCA1 increases overlap between memories after fear learning. This may create a system that is less precise but better suited for rapid detection and response to potential threats. The findings also highlight complementary roles within the hippocampus: dCA1 supports detailed contextual representations, whereas vCA1 integrates contextual and emotional information to enable rapid fear-memory retrieval.
What’s next
Future studies will examine how other hippocampal regions contribute to these processes and how threat-related representations change during fear extinction. Researchers also aim to understand how downstream regions, such as the amygdala and prefrontal cortex, use these hippocampal signals to control behaviour. Ultimately, this work provides a new framework for understanding emotional memory retrieval and may help guide future approaches for treating anxiety- and trauma-related disorders.
Read the article here:
Rozeske, R.R., Runtz, L., Lee, J.Q. et al. Overlapping representations in the ventral hippocampus support rapid fear memory retrieval. Nat Neurosci (2026). https://doi.org/10.1038/s41593-026-02435-5