In a mouse study conducted by researchers from the European Molecular Biology Laboratory, it was found that certain fears – physical pain, aggressive members of the same species and predators – activate different brain circuits, even though the mice reacted to the different threats identically.
Results of the study, which researchers say could help humans with phobias and panic attacks, are published in the journal Nature Neuroscience.
Bianca Silva worked with colleagues to carry out the work at the European Molecular Biology Laboratory (EMBL) in Italy, exposing mice to three threats:
- Another aggressive mouse
- A rat predator, or
- A mild electric shock to the feet.
In all situations, the mice showed consistent fearful reactions to the threats by running away or freezing. However, the scientists mapped the brain activity of the mice and found that their brains showed certain differences.
A region in the brain called the ventromedial hypothalamus (VMH) showed different parts that “lit up,” depending on the threat. The researchers say this region of the brain has “been implicated in feeding, sex and aggression.”
When the mice were faced with another aggressive mouse, the bottom and sides of the VMH were activated. However, when faced with the predator (rat), the central and upper areas of the VMH lit up.
And when the team blocked only the “rat fear” areas with drugs, the mice were no longer afraid of the rat but still feared the mouse. According to the researchers, this shows that the mice rely on this brain circuit to process predator fear.
“We found that there seems to be a circuit for handling fear of predators – which has been described anatomically as a kind of defense circuit – but fear of members of the same species uses the reproductive circuit instead,” says Silva, adding that “fear of pain goes through yet another part of the brain.”
According to the team, the human brain has similar circuits to those found in the mice.
Because we experience fears in a wide variety, these findings could help scientists develop treatments for certain phobias or panic attacks, simply by targeting the “relevant region” of the brain.
And the scientists have plans to dig deeper into how these fears work in the brain.
Cornelius Gross, who led the work at the EMBL, says that what his team is interested in is whether their results represent a mental state.
“If so,” he says, “mice should be able to be in that state without expressing it in their behavior – do they re-live that fear, for example? These are not easy questions to ask in the mouse, but we’re looking into them.”
Gross told Medical News Today about the kind of interventions that could potentially help humans as a result of their findings:
“Our findings suggest that drugs that inhibit the predator circuit might block fear associated with predator-like threats or their memories in humans – the monsters of our nightmares, menacing military vehicles – while drugs that inhibit the reproductive circuit might block fear associated with socially threatening situations, such as public speaking that is enhanced in persons with anxiety disorders like social phobia.”
Medical News Today recently reported on a study that suggested anxiety can cause the brain to transform neutral odors to negative ones, creating a “vicious cycle,” whereby stress is heightened.