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Scientists have found a way to flip the fear and courage switches in the brain

Authors of a new study say this development could help people who suffer from phobias, anxiety and PTSD.

Image: Shutterstock/Iurii Stepanov

SCIENTISTS MAY HAVE discovered a way to help people who suffer from anxiety, phobias or PTSD to cope better with stressful situations.

Researchers at the Stanford University School of Medicine have identified two adjacent clusters of nerve cells in the brains of mice whose activation levels to a visual threat spell the difference between a timid response and a bold or even fierce one.

The cell clusters are located in the middle of the brain and each send signals to different areas of the brain, igniting opposite behaviours in the face of a visual threat.

By selectively altering the activation levels of the two clusters, or nuclei, the investigators could prompt mice to freeze or duck into a hiding space, or to aggressively stand their ground, when approached by a simulated predator.

According to associate professor of neurobiology and of ophthalmology Andrew Huberman, human brains probably possess the same sort of circuitry. Finding ways of shifting the signal strengths of these nerve clusters either ahead of or during situations that people perceive as threatening may help those who suffer with excessive anxiety, phobias, or post-traumatic stress disorder.

“This opens the door to future work on how to shift us from paralysis and fear to being able to confront challenges in ways that make our lives better,” said Huberman, the senior author of a paper which was published in Nature this week.

As part of this study, lead author Lindsey Salay simulated a looming predator’s approach. Investigators selectively modified specific sets of nerve cells in the mice’s brains to simulate different responses.

For example, exclusively stimulating one cluster markedly increased the propensity to freeze in place.

However, boosting activity in the ‘courage’ nucleus resulted in a completely different result: The mice stood their ground, right out in the open and rattled their tails – an act associated with aggression in the species.

This “courageous” behaviour was unmistakable, and loud, Huberman said. “You could hear their tails thumping against the side of the chamber. It’s the mouse equivalent of slapping and beating your chest and saying, ‘OK, let’s fight!’” The mice in which this nucleus was stimulated also ran around more in the chamber’s open area, as opposed to simply running toward hiding places.

The research group is now exploring the efficacy of techniques such as deep breathing and relation of visual fixation in people who suffer with anxiety or PTSD. The thinking is that reducing signalling to the part of the brain which receives these messages or altering the balance of the strength of these signals could increase a person’s flexibility in coping with stress.

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