How a racing heart may alter decision-making

Anxiety, addiction, and other psychiatric disorders are often characterized by intense states of what scientists call arousal: The heart races, blood pressure readings rise, breaths shorten, and “bad” decisions are made. In an effort to understand how these states influence the brain’s decision-making processes, scientists at the Icahn School of Medicine at Mount Sinai analyzed the data from a previous study of non-human primates. They found that two of the brain’s decision-making centers contain neurons that may exclusively monitor the body’s internal dynamics. Furthermore, a heightened state of arousal appeared to rewire one of the centers by turning some decision-making neurons into internal state monitors.


“There is some evidence to support our hypothesis that the brain is designed to continuously monitor and integrate what is occurring within the body. The way these circuits function may thus be altered by changes in our degree of arousal “Dr. Peter Rudebeck, an associate professor in Mount Sinai’s Nash Family Department of Neuroscience and Friedman Brain Institute and the study’s principal author, agreed (Proceedings of the National Academy of Sciences). A deeper knowledge of brain regions and basic biological mechanisms behind many psychiatric diseases is the aim of these findings.

Atsushi Fujimoto, MD, PhD, an Instructor in Dr. Rudebeck’s lab, conducted the investigation. Dr. Fujimoto has previously researched how the brain regulates risk-taking behavior. A “U-shaped curve” has long been used by scientists to explain the connection between arousal and decision making ability. A little arousal, like the kind you get after drinking a cup of coffee, may help you perform at your best. However, when arousal levels are out of balance, the brain is more likely to make sluggish or erroneous choices. The study’s first findings backed up this hypothesis. The scientists reviewed data from a prior study in which they examined the decision-making abilities of three rhesus monkeys when given the choice between a large amount of delicious juice or a little amount. In his role as a postdoctoral researcher at the National Institute of Mental Health, Dr. Rudebeck carried out these studies while. Because the monkeys regularly opted to drink more juice, it seems that an aroused condition promotes greater performance. On average, they made this choice quicker when their hearts were pounding faster.

The next step was to examine the electrical activity of neurons in the orbitofrontal cortex and the dorsal anterior cingulate cortex, two of the brain’s decision-making regions. They discovered that variations in heart rate were linked with the activity of approximately a sixth of the neurons in each region. The activity of these cells would increase or decrease in accordance with changes in an animal’s heart rate. The monkeys’ behavior did not seem to be influenced by the choices made regarding the various incentives they received. While this was going on, it seemed that the activity of the remaining cells in each region was mainly focused on making decisions. “Bodily arousal affects the activity of these decision-making regions, according to brain scan research. According to our findings, certain neurons’ only function is to monitor the body’s interior states (known as interoceptive states) on a cellular level “According to Dr. Fujimoto’s statement, What could happen during heightened arousal levels observed in patients with anxiety, addiction, and other mental illnesses was the next concern we had,” says Dr. Smith.

For the purpose of finding an answer, scientists examined data collected after each animal’s amygdala, the brain’s emotional center, was surgically disabled. Blood pressure rose as much as 15 beats per minute as a result. The quicker the animals’ hearts raced while they were in this greater arousal state, the longer it took them to select a reward. This indicates that raising the animals’ arousal level actually made them less capable of making sound decisions. The researchers discovered something much more intriguing when they examined the brain activity. The increased level of arousal seemed to change the functions performed by neurons during decision-making. The number of neurons involved in decision-making was shown to be decreasing in both prefrontal and temporal lobes of the brain. Furthermore, the number of neurons that seemed to monitor internal states increased somewhat in the dorsal anterior cingulate cortex. This tipped the information distribution in this region, as if arousal had “hijacked” the brain signals used for decision-making. But even if this is not the case, Dr. Rudebeck believes his findings “indicate that increased arousal impairs decision-making” in the brain. In the future, researchers want to learn more about how arousal affects higher brain processes and how it relates to mental health issues.

Journal Reference: Atsushi Fujimoto, Elisabeth A. Murray, Peter H. Rudebeck. Interaction between decision-making and interoceptive representations of bodily arousal in frontal cortexProceedings of the National Academy of Sciences, 2021; 118 (35): e2014781118 DOI: 10.1073/pnas.2014781118

Categories: Clinical