A racing heart can alter the roles played by the neurons in the brain’s decision-making centers, thereby, hijacking our ability to make sound decisions, says a new study. 

Anxiety, addiction, and other psychiatric disorders can manifest themselves with intense states of arousal such as faster heart rate, elevated blood pressure, shortness of breath and making poor judgements. But how do these states affect the brain’s decision making processes? 

Body-state monitoring neurons under the influence of intense state of arousals such as a racing heart and high blood pressure, can put the decision-making processes in a shambles.
Body-state monitoring neurons under the influence of intense state of arousals such as a racing heart and high blood pressure, can put the decision-making processes in a shambles.

A paper published in the journal PNAS (Proceedings of the National Academy of Sciences) has revealed that a racing heart causes some of the brain’s decision-making circuits to monitor and integrate internal bodily operation instead of getting involved in decision making processes. 

The brain contains neurons that oversee the internal dynamics of our body, but under the influence of intense state of arousal, some decision-making neurons remodel themselves into internal state monitors.

“Our results suggest that the brain’s decision-making circuits may be wired to constantly monitor and integrate what is happening inside the body. Because of that, changes in our level of arousal can alter the way that these circuits work,” says Peter Rudebeck, PhD, the lead author of the study, in a news release. “We hope that these results will help researchers gain a better understanding of the brain areas and fundamental cellular processes that underlie several psychiatric disorders.”

For the study, the researchers explored the brain’s decision-making process through these bodily functions by assessing the data from a previous study on rhesus monkeys where they assayed their ability to decide between receiving two rewards: either a lot of tasty juice or a little. The monkeys, as it was expected, consistently chose to chug on more juice, and made this decision faster when their hearts were racing. 

Next they catalogued electrical activity from neurons in two of the brain’s decision centers – the orbitofrontal cortex and dorsal anterior cingulate cortex.

It was found that the activity of about a sixth of the neurons in either of the centers had correlations with fluctuated heart rate. 

Put simply, change in heart rate would evoke the activity of these cells to either speed up or slow down. This activity stayed intact when it came to making decisions about the different rewards the monkeys were receiving. Meanwhile, the activity of the remaining cells in each center appeared to be primarily engaged in the process of making decisions.

It’s been firmly established that racing heart alters the activity of our decision making centers, and as studies have shown, the responsibilities of some of these neurons is to monitor the body’s internal states. So what does this study say about people that have already been cursed with anxiety, addiction, and other psychiatric disorders during the intense state of arousal?

To answer that, the team tried surgically turning off the amygdala, the brain’s emotional center, in each monkey. It resulted in raised heart rates by upto 15 beats per minute. And now, in this even higher arousal state, the faster the heart beats, the slower it was for the monkeys to make a decision of choosing the reward. So, this was clearly indicative that a heightened arousal state actually impeded the decision-making process.

What’s more interesting? In both the decision centers, a lesser number of neurons took part in the decision-making process. Meanwhile, in the dorsal anterior cingulate cortex, more neurons took part in tracking internal states causing disarray in the balance of information represented in this decision center, as though the arousal had seized the neural signal for decision making. 

“Although not definitive, our results suggest that a heightened arousal state degrades and takes control of the decision-making circuits in the brain,” Dr. Rudebeck explains. “We plan to continue studying how arousal can influence higher brain functions and how this contributes to psychiatric disorders.”