July 1st, 2017

Area of brain impacts anxiety about the future, study says

A  group of researchers at Dartmouth College have found a connection between an area of the brain, the striatum, and a person’s intolerance of uncertainty – anxiety or worry about the unknown.

“We were interested in how uncertainty and ambiguity of potential future threat contribute to the generation of anxiety and how that might be represented in our brain,” said Justin Jim, Ph.D., lead author of the study, “Intolerance of Uncertainty Predicts Increased Stratial Volume,” which was published in the APA journal Emotion in May.

“For some individuals, the uncertainty of what ‘might happen’ tomorrow, is actually worse than the negative event itself actually happening. These individuals are intolerant of uncertainty,” he said by email.

Researchers took MRI scans of 61 Dartmouth College undergraduate students, ages 18-26, looking for brain regions whose size correlated with self-reported levels of intolerance of uncertainty, or IU.

“We found that individual differences in IU were positively correlated with only the volume of the striatum,” Kim said. “To put it another way, people who had difficulty tolerating an uncertain future had a relatively enlarged striatum, particularly a portion of the striatum called the putamen.”

The stratium is recognized for its role in motor function, and the ventral region of the stratium is important for reward processing, Kim said.

“The striatum encodes how predictable and expected a reward is – a higher form of reward processing compared to simply responding to a reward. Given that an important component of IU is a desire for predictability, our findings offer a neuroanatomical link related to our need for predictability – when we feel we know what will happen next, this decreases our baseline levels of anxiety, allowing us to focus and get our work done with less distraction.”

Previous studies have observed an enlarged stratium in those dealing with generalized anxiety disorder (GAD) or obsessive-compulsive disorder (OCD). This study suggests that the relationship between the size of the stratium and IU is relevant to all, not just those dealing with anxiety disorders.

“Our findings show that the size of the striatum reflects one’s personality characteristic – how you deal with an uncertain future, as measured as IU,” Kim said. “We also
found that an enlarged striatum is not unique to GAD or OCD, and rather it is related to IU, meaning that having an enlarged striatum does not necessarily indicate one has GAD or OCD. Having a relatively enlarged volume of the striatum may be associated with how intolerant you are when facing an uncertain future, but it does not mean you have GAD or OCD.”

It remains to be seen if this connection between the stratium and IU will help predict future onset of anxiety disorders, Kim said. “These findings will serve as a starting point for treating symptoms specific to GAD or OCD by targeting the striatum and tracking its volume over the course of treatment. As we learn more about the specific neurochemistry of the striatum, perhaps this will offer a clue for pharmacological interventions that might modulate striatal activity,” he said.

By Rivkela Brodsky

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