Anxiety can come from the heart, a mice study found
Anxiety – Many studies on mental health have been conducted over the last several decades with the objective of aiding millions of people worldwide.
Anxiety is one of the most common mental illnesses, affecting around 30% of people and causing their hearts to beat.
Some, on the other hand, think that their beating heart adds to their anxiety.
Until now, a new mouse study found that they both belonged to the same group.
A new finding
The study, published in the March 9 issue of Nature, shows that in high-risk settings, a beating heart sends signals to the brain, increasing anxiety.
The findings may offer a new perspective on understanding and treating anxiety disorders.
Scientists observed anxiety-like behavior in mice after artificially increasing their heart rates.
They then calmed the mice by turning off a part of their brain.
The brain and emotions
According to Stanford University neuroscientist Karl Deisseroth, William James, the pioneer of psychology, proposed that physical experiences may contribute to emotions in the brain.
In his 1890 book The Principles of Psychology, James created the thesis that emotion follows what the body goes through, writing:
“We feel sorry because we cry, angry because we strike, afraid because we tremble.”
Interoception is the phenomenon in which the brain feels impulses within the body.
Nevertheless, neuroscientist Anna Beyeler of the French National Institute of Health and Medical Research in Bordeaux feels that determining whether these experiences contribute to emotion is impossible.
Beyeler analyzes brain networks connected with emotion and makes the following comment on his findings:
“I’m sure a lot of people have thought of doing these experiments, but no one really had the tools.”
Read also: Insomnia linked to heart attacks in new studies
The new study
Karl Deisseroth spent the most of his career developing devices for this kind of study.
He is one of the scientists that developed optogenetics, a method that utilizes viruses to modify the genes of certain cells so that they respond to light flashes.
With a light switch, scientists can regulate the activity of the cells.
In the current work, Deisseroth and his colleagues used a tiny vest with a light to change the heart rhythm of a mouse with a genetically altered heart.
When the mouse was switched off, its heart rate was around 600 beats per minute.
At 900 beats per minute, the mouse’s heartbeat was synced with the flashing light.
“It’s a nice reasonable acceleration [one mouse] would encounter in a time of stress or fear,” said Deisseroth.
When their hearts began to speed, the mice began to exhibit anxiety-like behavior.
In stressful situations, mice tend to retreat to the walls and hide in dark corners.
In another instance, when pressing a water lever resulted in a little shock every now and again, mice with normal heart rates pressed on it without hesitation.
Mice with a pounding heart, on the other hand, would become thirsty.
“Everybody was expecting that, but it’s the first time that it has been clearly demonstrated,” said Beyeler.
The researchers analyzed the mice’s brains for areas that may be processing the increased heart rate.
One of the most notable signals, according to Deisseroth, came from the posterior insula.
“The insula was interesting because it’s highly connected with interoceptive circuitry,” he said.
“When we saw that signal, [our] interest was definitely piqued.”
Further optogenetics were utilized to suppress activity in the posterior insula, which lowered the mice’s anxiety-like behaviors.
Although their hearts were still hammering, the animals behaved normally, spending more time in open areas of the mazes and pressing water levers without reluctance.
According to Wen Chen, branch chief of basic medical research for complementary and integrative health at the National Center for Complementary and Integrative Health in Bethesda, the study’s findings caught the curiosity of many people.
“No matter what kind of meetings I go into, in the last two days, everybody brought up this paper,” said Chen.
The next step, according to Karl Deisseroth, is to look at other physical regions that may impact anxiety.
“We can feel it in our gut sometimes, or we can feel it in our neck or shoulders,” he said.
Using optogenetics, scientists may tense a mouse’s muscles or give it butterflies in the stomach to reveal new circuits that trigger fear or anxiety-like responses.
Yet, Beyeler believes that understanding the heart-brain connection might help doctors manage fear and anxiety.
The trip from the laboratory to the clinic, however, is more convoluted than the path from the heart to the head.
Image source: PETA