Scientists Artificially Raise Mouse Heartbeats: What Study Means for Us

Scientists Artificially Raise Mouse Heartbeats: What Study Means for Us

Anxiety can be created by the body, according to a recent study with mice that may have significant implications for humans.

The research, published in the journal Nature , demonstrated that artificially raising a mouse’s heart rate leads to anxious behavior in the rodent.

Scientists have long known that emotional states influence our bodily physiologically. But whether or not an increased heart rate might induce anxiety, or fear itself, has remained unclear.

“This paper addresses a long-standing question that has inspired us in the lab, dating back at least to [American philosopher and psychologist] William James,” Karl Deisseroth, an author of the Nature study at Stanford University , told Newsweek . “In 1884, James posited that bodily changes represent emotion, and that the brain’s perception and experience of these changes is the emotion, in a fundamental way.”

Newsweek Newsletter sign-up >

“As a psychiatry doctor in training 20 years ago, I was intrigued by epidemiology linking primary cardiac disorders with panic attacks,” he said. “But there was no way of proving a causal link arising from cardiac abnormalities, since there was no way of specifically and directly controlling cardiac function in real time in behaving animals.” An artist’s illustration of the human heart and brain. “This work reinforces the notion that autonomically controlled organs like the heart also transmit information about their state to the brain, which integrates this information with other sources to influence emotion,” one academic concluded. Previously, the available pharmacological and electrical interventions couldn’t be shown to have specific direct action on the heart muscle cells themselves.

“It took my lab’s development over 20 years of optogenetics—a way of controlling specific cells with light––and in particular a fast and non-invasive form of optogenetics that we developed over the past three years to enable these experiments,” said Deisseroth, who is affiliated with Stanford’s Department of Bioengineering, as well as the college’s Department of Psychiatry and Behavioral Sciences.

Newsweek subscription offers >

The researchers developed a non-invasive optogenetic pacemaker that enabled them to precisely control the cardiac rhythms of lab mice and make their hearts beat faster—up to 900 beats per minute. For context, a normal resting heart rate for a mouse usually hovers around 600 beats per minute.

“We found that directly pacing the heart at higher rates caused increases in anxiety-related symptoms, especially in potentially risky environments,” Deisseroth said. “This effect was mediated by communication from heart muscle-cell activity to the insular cortex in the brain.”

The Nature study demonstrates that cells outside the brain play an important role in setting emotional states.

“This could be a general principle, since many emotions are felt in the body—not just anxiety and fear and rage, but also positive emotions relating to reward and social bonding,” Deisseroth said.

The results of the study show that the insular cortex is the main area of the brain involved in the processes described, “concluding that both brain and body are mutually involved in the origins of emotional states,” Dr. Antonio Giordano, president of the Philadelphia-based Sbarro Health Research Organization, who was not involved in the Nature paper, told Newsweek .

The issue of the relationship between largely unconscious processes regulated by the autonomic nervous system—for example, the heartbeat, the gastrointestinal tract, etcetera—and emotions has been an area of debate going back to James’s theory.

Sometimes referred to as the James-Lange theory, this idea posited that emotional sensations are the sum of the autonomic sensations that an activity arouses, Clifford Saper, a professor of neurology and neuroscience at Harvard Medical School, who was also not involved in the Nature paper, told Newsweek .

“Under this theory when you see a bear, you are afraid,” Saper said. “But the feeling of fear is produced by the cerebral cortex seeing something threatening, setting off changes in heart rate, blood pressure, breathing, etcetera, in response to seeing a bear, and that the ‘feeling’ you get is the sum of the sensations produced by the autonomic response.”

“This paper studies the way that the brain reacts to a stressful stimulus, showing that the brain sensation of the changes in heart rate augment the emotional response—although may not be the sole cause of it. It is a well done study by a very strong group of scientists.”

Deisseroth said it is “quite likely” that the study’s findings could be applicable to humans as well, even though these animals are not perfect model.

“The same basic circuitry is present in both species, and human epidemiology—the source of my initial psychiatric inspiration—strongly correlates primary cardiac disorders and anxiety symptoms, including panic attacks,” Deisseroth said.

Vasanth Vedantham, a professor of medicine at the University of California , San Francisco, who was not involved in the Nature study, told Newsweek that the paper’s authors used “innovative” methods and that the main finding is generally “well-supported” by the data.

“The result itself is not necessarily surprising and fits with current thinking about the relevance of bodily states to determination of the state of arousal—what is important is that the methods used can be generalized and will allow for a deeper exploration of the mechanistic pathways in the heart and nervous system that are involved in this processing,” he said.

“Thus, this work creatively circumvents experimental obstacles in this field and will open a new path to developing a detailed understanding of how bodily states influence the mind and its emotional states.”

The study provides some experimental support for the notion that the relationship between emotional states and the body involves a two-way flow of information, according to Vedantham.

“We are familiar with the notion that information taken in via sensory organs—vision, hearing, touch, etcetera—is processed and interpreted in the brain to influence our emotional states. This work reinforces the notion that autonomically controlled organs like the heart also transmit information about their state to the brain, which integrates this information with other sources to influence emotion—so the brain combines ‘external perception’ with ‘internal perception,'” he said.

“Importantly, the brain also influences the function of these organs so there is the potential for feedback. Thus, when we try to understand the factors that influence […]


Spread the love

Leave a Reply

Nature Knows Nootropics