How a racing heart may alter decision-making brain circuits
Body-state monitoring neurons can hijack the decision-making process


Date:
August 30, 2021
Source:
The Mount Sinai Hospital / Mount Sinai School of Medicine
Summary:
In an effort to understand how the internal state of the body
influences the brain's decision-making processes, scientists
analyzed the data from a previous study pre-clinical study. 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.



FULL STORY ========================================================================== [Human heart beats | Credit: (c) Sergey Nivens / stock.adobe.com] Human
heart beats illustration (stock image).

Credit: (c) Sergey Nivens / stock.adobe.com [Human heart beats | Credit:
(c) Sergey Nivens / stock.adobe.com] Human heart beats illustration
(stock image).

Credit: (c) Sergey Nivens / stock.adobe.com Close 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.


==========================================================================
"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," said Peter Rudebeck, PhD, Associate Professor in the Nash Family Department of Neuroscience and Friedman Brain Institute at Mount Sinai and the senior author of the study published in
PNAS (Proceedings of the National Academy of Sciences). "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." The study was led by Atsushi Fujimoto, MD, PhD,
an Instructor in Dr. Rudebeck's lab who previously studied how the brain controls risk-taking.

For years scientists have described the relationship between arousal and decision-making performance as a "U-shaped curve." Basically, a little of
bit of arousal -- such as that experienced after a cup of coffee -- might produce peak performance. But too much or too little arousal increases
the chances that the brain will make slow or incorrect decisions.

Initial results from this study supported this idea. The researchers
analyzed data from a previous set of experiments that tested the ability
of three rhesus monkeys to decide between receiving two rewards: either a
lot of tasty juice or a little. Dr. Rudebeck performed these experiments
while working as a post- doctoral fellow at the National Institute of
Mental Health. As expected, the monkeys consistently chose to have more
juice, and on average they made this decision faster when their hearts
were beating faster, supporting the idea that an aroused state fosters
better performance.

Next, the researchers analyzed the electrical activity recorded from
neurons in two of the brain's decision centers called the orbitofrontal
cortex and dorsal anterior cingulate cortex.

They found that the activity of about a sixth of the neurons in either
area correlated with fluctuations in heart rate. In other words, if an
animal's heart rate changed, then the activity of these cells would also
change by either speeding up or slowing down. This activity appeared
to be unaffected by the decisions made about the different rewards that
the monkeys were receiving.

Meanwhile, the activity of the remaining cells in each area appeared to
be primarily involved in the decision-making process.

"Brain scanning studies have suggested that bodily arousal alters the
activity of these decision-making centers. Our results both support
this idea on a cellular level and suggest that the sole job of some
these neurons is to track the body's internal, or interoceptive,
states," Dr. Fujimoto said. "The next question we had was: 'What might
happen during the type of heightened arousal states seen in patients
who suffer from anxiety, addiction, and other psychiatric disorders?'"
To answer the question, the researchers analyzed the data obtained after
the amygdala, the brain's emotional center, was surgically turned off in
each animal. This raised heart rates by up to 15 beats per minute. Now, in
this higher arousal state, the faster the animals' hearts beat, the slower
they were to choose a reward. This suggests that when the animals' arousal state was heightened, it actually hampered the decision-making process.

When the team looked at the neural activity, they found something even
more interesting. The heightened arousal state appeared to alter the
roles that the neurons played during decision-making. In both brain
centers, the researchers saw evidence of a decrease in the number of
neurons involved in the decision- making process. Moreover, in the dorsal anterior cingulate cortex, the number of neurons that appeared to track internal states rose slightly. This altered the balance of information represented in this area, as if the neural signals for decision making
were "hijacked" by arousal.

"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 said. "We plan to continue studying how arousal can influence
higher brain functions and how this contributes to psychiatric disorders."
This study was supported by the National Institutes of Health (MH110822),
the NIH's BRAIN Initiative (MH117040), the NIH Intramural Research Program
at the National Institute of Mental Health (MH002886), the Takeda Science Foundation, and a Brain & Behavior Research Foundation Young Investigator
Grant (#28979).

========================================================================== Story Source: Materials provided by The_Mount_Sinai_Hospital_/_Mount_Sinai_School_of Medicine. Note: Content
may be edited for style and length.


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

Link to news story: https://www.sciencedaily.com/releases/2021/08/210830140224.htm

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