How micro-circuits in the brain regulate fear
Fear is an important reaction that warns and protects us from danger. But when fear responses are out of control, this can lead to persistent fears and anxiety disorders.

Recent studies have shown that certain groups of neurons in the amygdala are crucial for the regulation of fear responses. The amygdala is a small almond-shaped brain structure in the center of the brain that receives information about fearful stimuli and transmits it to other brain regions to generate fear responses. This causes the body to release stress hormones, change heart rate, or trigger fight, flight, or freeze responses.

Researchers have discovered that the amygdala plays a much more active role in these processes than previously thought: Not only is the central amygdala a "hub" to generate fear responses, but it contains neuronal microcircuits that regulate the suppression of fear responses.

In animal models, it has been shown that inhibition of these microcircuits leads to long-lasting fear behavior. However, when they are activated, behavior returns to normal despite previous fear responses. This shows that neurons in the central amygdala are highly adaptive and essential for suppressing fear. These results were published in the journal Nature Communications.

For their study, the researchers used several methods, including a technique called optogenetics with which they could precisely shut down—with pulses of light—the activity of an identified neuronal population within the central amygdala that produces a specific enzyme. This impaired the suppression of fear responses, whereupon animals became excessively fearful.

In humans, dysfunction of this system, including deficient plasticity in the nerve cells of the central amygdala described here, could contribute to the impaired suppression of fear memories reported in patients with anxiety and trauma-related disorders. A better understanding of these processes will help develop more specific therapies for these disorders.

Nature Communications
Source: https://doi.org/10.1038/s41467-021-24068-x
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