We all experience anxiety from time to time. In “normal” amounts, it is a healthy feeling which warns us of potential dangers or motivates us to get things done. A moderate level of anxiety may in fact improve performance in many areas. In the average individual, occasional anxiety is simply part of the human condition. For many people around the world, however, anxiety is a plague. Excessive anxiety can be debilitating in the workplace, school environment, social network, and home. It can affect job and academic performance, and negatively impact our interpersonal relationships. In extreme cases, it can even make leaving the home a terrifying experience. We probably all know someone who lives and suffers with clinically significant levels of anxiety every day.
A variety of treatment options are available, from psychotherapy to psychopharmacological interventions. Anxiety is still being studied extensively, in order to further our knowledge and understanding, and to discover new treatment methods and options.
A couple of recent studies offer information on some relatively new developments.
One group of scientists chose to experiment on zebrafish due to brain similarities between zebrafish and mammals. Their research provides us with new information on the way in which anxiety is regulated in vertebrates, and shows how the normally functioning brain shuts down anxiety responses.
The team of scientists, led by Dr Suresh Jesuthasan from the A*STAR/Duke-NUS NRP, showed that disrupting a specific set of neurons in the habenula prevents normal response to stressful situations. In their experiments, Dr Jesuthasan’s team trained larval zebrafish to swim away from a light in order to avoid a mild electric shock. While normal fish easily learned this task, fish that had a specific set of neurons in the habenula damaged displayed signs of “helplessness.”
Although they initially tried to avoid the shock, they soon gave up. What’s more, these fish showed indications that they were more anxious than normal fish, such as being startled easily by non-harmful stimuli. Because of the similarity of the zebrafish brain to the mammalian brain, the study suggests that malfunction of the habenula is a possible cause of certain anxiety disorders in humans. This means that it may be possible to use direct stimulation of the habenula as a way of treating some types of anxiety disorders in humans. The zebrafish model which the scientists developed in the course of their work may also be used in future drug discovery efforts for psychiatric medicines.
Science Daily, emphasis added
In other developments, a new study indicates that researchers can turn a mouse’s anxiety response off or on by lighting up a connection in the brain.
The results, reported online March 9 in Nature, “gets us that much closer to understanding how the [anxiety] system works or how it doesn’t work in clinical cases,” says neuroscientist and psychiatrist Kerry Ressler, a Howard Hughes Medical Institute investigator at Emory University in Atlanta who was not involved in the study. The results, he says, will help researchers gain a deeper understanding of circuits in the human brain important for psychiatric disorders.
The new study focused on the amygdalae, a pair of structures buried deep within the brain, one on each side. These bundles of nerve cells are important for emotions, including fear, but it’s been less clear what role this brain region plays in anxiety, which unlike fear doesn’t require a specific trigger.
[. . .]
A particular connection – the place where cells in the basolateral part of the amygdala connect to the central amygdala – was the anxiety sweet spot, the researchers found. Normally, mice are afraid of wide-open spaces, where they could be nabbed by a cat or a bird. When given a choice in lab tests, mice spend most of the time hunkered down in a platform area with walls avoiding open areas. But when the connection between these two amygdala neighborhoods was boosted with a burst of light, mice quickly began exploring the formerly frightening areas. When the light was turned off, the mice retreated to the walled areas.
The opposite was also true, the team found. In another experiment, dampening the connection between the two amygdala regions made mice less likely to venture out from the walled areas. “It seems as though within the amygdala, there’s a real-time dial for turning down anxiety,” Deisseroth says.Science News, emphasis added
Watch a video showing a mouse being tested in a maze before and after light stimulation to the amygdala here.
These are but two recent studies in the ongoing quest to better understand the phenomenon of anxiety. Hopefully in time what scientists have discovered here will have implications for and direct applications to human populations.
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