How Fear Blurs the Line Between Safety and Danger - Space and astronomy

A study in mice found that memories of threatening and safe environments became less distinct, potentially helping the brain retrieve fear memories faster. The researchers say this may offer a new way to understand fear responses in anxiety and PTSD, but further research is needed to establish whether the same mechanism operates in people.

Fear may make the brain’s memories of danger and safety overlap rather than keeping them sharply separate, according to a study by researchers at McGill University’s Douglas Research Centre and the University of Toronto Scarborough. The findings suggest this may help explain why people with anxiety or post-traumatic stress disorder (PTSD) can feel intense fear in situations that are safe.

In experiments with mice, the researchers trained the animals to associate one environment with danger and another with safety. The brain activity associated with the two environments became less distinct over time, rather than forming increasingly separate patterns. The study was published in Nature Neuroscience.

To track the changes, the team used an augmented-reality arena that let them alter the sights and sounds around the mice, creating the experience of moving between environments without physically relocating them. Miniature microscopes recorded activity in hundreds of neurons in the hippocampus, a region involved in learning and memory.

The researchers suggest that overlapping representations may allow the brain to retrieve information about past threats more quickly. That speed could be useful when danger is real, but it may also make the brain more likely to respond defensively to a harmless situation—a trade-off between rapid reaction and precision.

The team says the findings could help explain how reminders of trauma, including a sight, sound or setting, might trigger fear even when there is no immediate threat. They propose that such reactions could involve an ordinary survival response becoming overly sensitive, rather than simply a failure to distinguish memories.

Because the experiments were conducted in mice, further research is needed to determine whether the same process contributes to anxiety and PTSD in humans. The study, “Overlapping representations in the ventral hippocampus support rapid fear memory retrieval,” received support from the Canadian Institutes of Health Research and the Natural Sciences and Engineering Research Council of Canada.

Sources: ScienceDaily.