The amygdala is one of two almond-shaped clusters of nuclei located in the center of the brain and is part of the limbic system
via Life Science Databases / Wikicommons (CC BY-SA 2.1 JP)
The brain mechanisms underlying the suppression of fear responses have attracted a lot of attention as they are relevant for therapy of human anxiety disorders.
Despite our broad understanding of the different brain regions activated during the experience of fear, how fear responses can be suppressed remains largely elusive. Researchers at the University of Bern and the Friedrich Miescher Institute in Basel have now discovered that the activation of identified central amygdala neurons can suppress fear responses.
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. In Europe, about 15 percent of the population is affected by anxiety disorders. Existing therapies remain largely unspecific or are not generally effective, because the detailed neurobiological understanding of these disorders is lacking.
What was known so far is that distinct nerve cells interact together to regulate fear responses by promoting or suppressing them. Different circuits of nerve cells are involved in this process. A kind of “tug-of-war” takes place, with one brain circuit “winning” and overriding the other, depending on the context. If this system is disturbed, for example if fear reactions are no longer suppressed, this can lead to 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 freezing responses. Now, a group led by Professors Stéphane Ciocchi of the University of Bern and Andreas Lüthi of the Friedrich Miescher Institute in Basel has 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 behaviour. However, when they are activated, behaviour 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.
“Disturbed” suppression leads to long-lasting fear
The researchers led by Stéphane Ciocchi and Andreas Lüthi studied the activity of neurons of the central amygdala in mice during the suppression of fear responses. They were able to identify different cell types that influence the animals’ behaviour. 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. “We were surprised how strongly our targeted intervention in specific cell types of the central amygdala affected fear responses,” says Ciocchi, Assistant Professor at the Institute of Physiology, University of Bern. “The optogenetic silencing of these specific neurons completely abolished the suppression of fear and provoked a state of pathological fear.”
Important for developing more effective therapies
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. “However, further studies are necessary to investigate whether discoveries obtained in simple animal models can be extrapolated to human anxiety disorders”, Ciocchi adds.
Original Article: How micro-circuits in the brain regulate fear
The Latest Updates from Bing News & Google News
Go deeper with Bing News on:
Suppression of fear responses
- Essence Of Speeches Of Accused To Instill Fear Among Muslims During 2020 Riots: Delhi Police
The Delhi Police has said that the speeches delivered by various accused of conspiracy during the 2020 communal riots were intended to instill fear among the Muslim populace.
- Of Course Biden Has Rebound COVID
When Biden got sick last week, he started taking the pills before the day was out. When Anthony Fauci had COVID in June, he took two courses. That enthusiasm is in line with the government’s messaging ...
- Canada takes action by endorsing global declaration on Undetectable = Untransmittable (U=U)
U=U accelerates progress towards national and global goals to end the HIV epidemic MONTREAL, /CNW Telbec/ - Public Health Agency of Canada Thanks to the advances in HIV science over the last four ...
- Staked Ether (stETH) And The Curious Case Of Depegging
What exactly is stETH in relation to ETH, and what is its role in crypto contagion that has been plaguing the crypto sector throughout May, June and July?
- WVU researcher finds fears of workplace discrimination drive performance challenges for employees with mental illnesses
An employee’s diagnosis of depression or bipolar disorder can spark a fear of discrimination in the workplace, prompting the employee to construct an inauthentic professional identity, according to ...
Go deeper with Google Headlines on:
Suppression of fear responses
Go deeper with Bing News on:
Human anxiety disorders
- The Human Cost of Restricting Abortion
Growing up unwanted can leave scars that last into adulthood.
- New study suggests B6 supplements could help to relieve symptoms of anxiety and depression
New research suggests Vitamin B6 supplements could help to treat and alleviate symptoms of anxiety and depression, read how the science stacks up.
- Anxiety drives amygdala differences in autistic youth
Regions of the brain’s fear center expand in autistic children and teenagers with anxiety, but not in their autistic or non-autistic peers without anxiety.
- High-dose supplementation of Vitamin B6 decreases anxiety
As such, it has been suggested that supplementing with high-dose vitamin B might effectively augment behaviorally noticeable effects of inhibition. In one study, subjects were supplemented with ...
- Vitamin B6 helps in easing depression and anxiety symptoms: Research
Anxiety and depression symptoms can be reduced by using high-dose vitamin B6 pills, as per a recent study. Journal of Human Psychopharmacology Clinical and Experimental reported the study's findings.