Scientists have found neurons that prevent mice from forming fearful memories in an area of the brain called the hippocampus.
These inhibitory neurons ensure that a neutral memory of a context or location is not contaminated by an unpleasant event occurring at the same time.
The team says their work could one day help them better understand the neural basis of conditions such as post traumatic stress disorder.
The study is published in Science.
Attila Losonczy, from Columbia University in New York and colleagues, were interested in how the hippocampus stores memories of a particular context and then separates this memory from a fearful event.
When looking at individual neurons in the brains of mice, they found inhibitory cells - called interneurons - were crucial for fear memory formation to travel to the correct part of the brain.
"These cells are activated by the unpleasant salient event and they act somewhat like a filter. They may function to block out unwanted information related to this strong, salient event," Dr Losonczy told the BBC's Science in Action programme.
Stopping fear "This way, the hippocampus can process and store contextual information reliably and independently without the potentially detrimental interference from this [unpleasant] salient event," he added.
When mice were conditioned to express fear in a particular context, they later associated the same environment with the unpleasant event.
But when scientists deactivated these inhibitor neurons, the mice no longer showed any fear. That is, the team was able to stop the mice from forming fearful memories ( via bbc.co.uk ).