A team of scientists has discovered the brain mechanisms that allow animals to suppress the instinctive responses of fear, a finding that could help develop therapies to treat posttraumatic stress disorder (PTSP) and anxiety.
The details of the study, conducted by researchers from the Sainsbury Wellcoma Center (SWC) of University College in London, have been published in the Science magazine.
“Human beings are born with instinctive fear reactionsfor example, before strong noises or objects that are quickly approaching, ”explains Sara Mederos, a researcher at the SWC and co -author of the study.
However, we can cancel these instinctive responses through experience, such as when children learn to enjoy fireworks instead of fearing their rumble. We wanted to understand the brain mechanisms that underlie these forms of learning. ”
To study how the brain learns to suppress answers to perceived threats, the team studied mice to which an expanding shadow was presented that imitated an air predator that was approaching.
At first, the mice were sought for refuge in this visual threat, but, after several exhibitions and without real danger, they learned to remain calm instead of escaping, which provided researchers A model to study The suppression of fear responses.
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Experiments with responses to fear
For previous studies, they knew that an area of the brain called ventrolateral geniculate (VLGN) could suppress fear reactions when it was active and track knowledge of previous threat experiences.
VLGN also receives information from visual areas of the cerebral cortex, so researchers studied whether this neuronal route I played a role in learning not to fear a visual threat.
The study discovered two key points in this learning process: what specific regions of the visual cortex are essential for the learning process, and that the VLNG keeps these memories induced by learning.
We discovered that animals did not learn to suppress their fear responses when specific cortical visual areas were inactivated. However, once the animals had already learned to stop escaping, the cerebral cortex was no longer necessary, ”Mederos explained.
“Our results question traditional ideas about learning and memory,” says Professor Hofer, lead author of the study.
In addition, researchers also discovered the cellular and molecular mechanisms that underlie this process.
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The role of VLGN in learning
Learning is produced by an increase in neuronal activity in certain VLGN neurons, triggered by the release of endocannabinoids, internal messenger molecules of the brain known for regulating mood and memory.
This release decreases inhibitory entry to VLGN neurons, which involves greater activity in this area of the brain when the visual threat stimulus is located, which suppresses fear responses.
Implications to treat anxiety disorders
The authors suggest that the implications of this discovery go beyond the laboratory.
Our findings could help better understand what fails in the brain when the regulation of fear response is altered in diseases such as phobias, anxiety, and PTSD.
Although instinctive reactions of fear of predators can be less relevant to modern humans, the brain path that we have discovered also exists in humans, ”says Hofer.
“This could open new ways to treat fear disorders acting on the VLGN circuits or localized endocannabinoid systems.”
The team now plans to collaborate with clinical researchers to study these brain circuits in humans, with the hope of developing new and specific treatments for the miscarriage of fear and anxiety disorders.
(With EFE information)
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