Scientists indicate that the brain senses danger in a fraction of a second, but the fear can last much longer. They have discovered a region in the brain that prevents this feeling from fading until the threat has completely disappeared.According to scientists, nerve
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Best Top Supplements for Improve Women Uterine Health cells in the amygdala, responsible for triggering fear, respond to a threat signal within fractions of a second. The body remains on alert for tens of seconds, but until now it was unclear exactly what maintains this state.
According to the journal Neuron, researchers from the Salk Institute for Biological Studies discovered that the amygdala transition zone, or ASt, is responsible for this. It is a small group of cells located between the amygdala and the striatum, a brain region responsible for motor control. The ASt region possesses a unique set of genes, and experiments have shown that these genes directly influence the response to danger.
Researchers, after studying the genetic material of 97,434 brain nuclei in mice, including ASt cells, discovered that this region differs significantly from its surroundings. It contains a very high concentration of Drd2 dopamine receptor-positive neurons, which are dopamine-sensitive cells. These cells constituted approximately 71% of the cells in the ASt region, while Drd1a neurons made up only 26%.
Experiments measuring the electrical activity of ASt cells in 15 mice, after playing two sounds to the animals—one predicting an electric shock and the other a sweet reward—showed that ASt cells responded significantly to the threat and remained active for 20 seconds, while amygdala cells responded with only a brief pulse. When the mice calmed down, ASt cell activity more than tripled.
To confirm that the ASt region does indeed control behavior, scientists used optogenetics, a technique that allows neurons to be switched on and off using light. The researchers used a blue laser to activate the ASt region in 18 mice. With continuous stimulation, the mice immediately froze in place, while with localized stimulation, they avoided the laser beam.
Activating Drd2 neurons alone produced the same effect, while activating Drd1a cells had no effect on behavior. A balance test on a rotating device confirmed that the mice's cessation of movement was a threat response, not a loss of mobility. Inhibiting Drd2 cells also reduced the threat response by approximately 50%, without affecting the reward response or motor activity.
The scientists point out that their work is limited, as they tested only one type of threat and reward, and the ASt region was activated in response to an auditory cue, not in an environment that mice typically associate with fear. This suggests that this brain region responds specifically to sensory stimuli, rather than to the environment as a whole.
Therefore, the team plans to test whether the study's findings apply to humans, because understanding the mechanisms of fear is important for treating post-traumatic stress disorder and anxiety disorders, where these responses become persistent.
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