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Study Explores The Effect Of Stress On The Brain

We all get anxious from time to time, but what happens in the brain when this dreaded feeling looms? New research helps to answer this question.
In a study of monkeys, Ilya Monosov, Ph.D., of the Departments of Neuroscience and Biomedical Engineering at Washington University in St. Louis, MO, discovered specific cells in the brain that are activated in response to anxiety.
The researcher recently published his findings in the journal Nature Communications.
In simple terms, anxiety is defined as feelings of worry, nervousness, or fear about an event or situation that could yield an unpleasant outcome, such as a job interview or an exam.
While these feelings may quickly subside for some people, others may develop anxiety disorders, wherein anxiety persists or worsens over time.
According to the Anxiety and Depression Association of America, anxiety disorders affect around 40 million adults in the United States.
Dr. Monosov believes that his new study may open the door to new treatments for anxiety disorders, after identifying a group of brain cells that play a role in anxious feelings.
Dr. Monosov came to his findings by studying the brains of rhesus monkeys, which have many brain structures similar to those of humans.
He focused on the anterior cingulate cortex (ACC) of the brain, a region in the prefrontal cortex that previous studies have shown plays a role in behaviors associated with uncertainty – a key driver of anxiety.
For his study, Dr. Monosov trained two monkeys to associate three different geometric patterns with three different outcomes. One pattern was associated with receiving an irritating puff of air in the face (representing a certain outcome), one pattern was associated with a 50-50 likelihood of getting a puff of air in the face (representing an uncertain outcome), while the third pattern was associated with no outcome.
As the monkeys were shown each geometric pattern, Dr. Monosov used MRI to measure neuronal activity in the ACC of their brains.
The researcher identified brain cells in the ACC that were activated in response to the geometric design associated with an uncertain outcome. However, when the monkeys were shown patterns associated with a certain outcome or no outcome, these brain cells showed no activity.
“We found a population of neurons that activated specifically when monkeys thought something bad or annoying – like a puff of air to the face – might be coming, but not when they knew for certain it was,” explains Dr. Monosov.
In another experiment, Dr. Monosov trained the monkeys to recognize two geometric patterns associated with the certainty or possibility of receiving a sip of juice, representing a positive outcome.
The results were similar to those seen in the first experiment: when the monkeys were presented with an uncertain outcome, a specific group of brain cells in the ACC were activated. These cells were not activated when the monkeys were presented with the certain outcome.
According to Dr. Monosov, these findings not only help to explain the brain mechanisms that underlie anxiety, but they may also pave the way for new treatments for anxiety and other behavioral disorders.
“Now that we know which cells are active when an animal is faced with the uncertainty of a bad experience, we can try to disrupt the activity of these cells. It opens up avenues of research, which may one day lead to new ways to treat disorders such as anxiety and depression” saysIlya Monosov, Ph.D.