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 How a racing heart can have an impact on the brain circuits that are responsible for making decisions



Introduction


When it comes to anxiety, addiction, and other psychiatric disorders, high levels of arousal are frequently present: It causes the heart to beat faster, the blood pressure to rise, the breaths to become shallow, and "bad" decisions to be made. Researchers at Mount Sinai's Icahn School of Medicine examined data from a previous study of non-human primates in order to gain a better understanding of how these states affect the brain's decision-making processes. They discovered that neurons in two of the brain's decision-making centers may be dedicated to monitoring the internal dynamics of the body, according to their findings. Increased arousal appeared to have rewired one of the centers, converting some decision-making neurons into internal state monitors, which appeared to have rewired another center.


Findings 


"Our findings suggest that the brain's decision-making circuits may be wired in such a way that they are constantly monitoring and integrating information from within the body, which is consistent with previous research. Therefore, changes in our level of arousal can have an impact on the way these circuits operate." According to Peter Rudebeck, PhD, an associate professor in Mount Sinai's Nash Family Department of Neuroscience and Friedman Brain Institute and the senior author of the study published in the journal PNAS, the findings of the study were unexpected (Proceedings of the National Academy of Sciences). "We anticipate that these findings will assist researchers in developing a better understanding of the brain regions and fundamental cellular processes that underlie a variety of psychiatric disorders."


In this study, Atsushi Fujimoto, MD, PhD, an Instructor in Dr. Rudebeck's lab who has previously investigated how the brain regulates risk-taking, served as the study's principal investigator.


Scientists have been describing the relationship between arousal and decision-making performance with the term "U-shaped curve" for many years. It is possible to achieve peak performance with only a small amount of physical or mental arousal, such as that experienced after drinking a cup of coffee. Excessive or insufficient arousal, on the other hand, increases the likelihood that the brain will make decisions that are slow or incorrect.


Initially, the findings of the study confirmed that this hypothesis was correct. A previous set of experiments in which the researchers evaluated three rhesus monkeys' ability to choose between receiving a large amount of tasty juice or a small amount was examined by the researchers. The researchers analyzed data from this previous set of experiments. In his post-doctoral fellowship at the National Institute of Mental Health, Dr. Rudebeck carried out the experiments that were the subject of this paper. Exactly as predicted, the monkeys consistently chose more juice, and on average, they made this choice faster when their hearts were racing, supporting the notion that being in a highly aroused state promotes superior performance.


Later, the researchers looked at the electrical activity of neurons in two of the brain's decision-making centers, the orbitofrontal cortex and the dorsal anterior cingulate cortex, to see what was going on.


During their research, they discovered that approximately a sixth of the neurons in each area correlated with fluctuations in heart rate. This means that whenever the heart rate of an animal changes, the activity of these cells changes as well, and this activity can be either increased or decreased. This activity did not appear to be affected by the choices made by the monkeys regarding the various rewards that they were offered. The remaining cells in each area, on the other hand, appeared to be preoccupied with decision-making.


"In accordance with brain scanning studies, physical arousal alters the activity of these decision-making centers. According to our findings, some of these neurons' sole function is to monitor the body's internal, or interoceptive, states, which both confirm and imply that this is the case. " Dr. Fujimoto's opinion is that What might happen during the type of heightened arousal states observed in patients with anxiety, addiction, and other psychiatric disorders was the question that was asked.


This question was answered by looking at data collected after each animal's amygdala, or emotional center of the brain, was surgically disabled. Heart rates rose by up to 15 beats per minute as a result of this, according to the study. After that, the higher the animals' level of arousal, the slower their hearts beat and the longer it took them to choose a reward. This indicates that raising the animals' level of arousal had the opposite effect of improving their decision-making process.


Researchers discovered something even more fascinating when they investigated neural activity in greater depth. The increased level of arousal appeared to have an effect on the roles played by neurons during the decision-making process. A decrease in the number of neurons involved in decision-making was observed in both brain centers, according to the researchers. In addition, the number of neurons in the dorsal anterior cingulate cortex that appeared to track internal states increased slightly in the study participants. As if arousal had "hijacked" the neural signals responsible for decision-making, the balance of information represented in this area was altered as a result of this.


In Conclusion


Despite the fact that the findings are not conclusive, Dr. Rudebeck stated that "increased arousal degrades and takes control of the brain's decision-making circuits." Our research will continue into the ways in which arousal affects higher brain functions, and how this influences the development of psychiatric disorders in the future.

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