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In depressed people, the medial prefrontal cortex exerts more control over other parts of the brain

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New neuroimaging research has found that depression is associated with abnormal function in an area of the brain known as the medial prefrontal cortex.

The study, published in the American Journal of Psychiatry, investigated how the medial prefrontal cortex interacted with other areas of the brain in depression.

“I was keen to explore the connection between recent brain findings in depression and the disturbances in the way the self is experienced in depression. Imaging studies over the past 10 years have shown that brain regions that are involved in self-related processing are often affected by depression, and it seemed possible that the two sets of findings were related,” explained Christopher G. Davey of the University of Melbourne, the study’s corresponding author.

“We wanted to apply sophisticated computational brain modelling to understanding the relationship: not simply whether regions of the brain were over- or under-activated in depression, but how depression affected the way brain regions connected with, and influenced, other brain regions.”

Davey and his colleagues were particularly interested in the medial prefrontal cortex because previous research had found that this region was associated with self-consciousness and self-related mental processes.

The researchers used functional magnetic resonance imaging (fMRI) to compare the brain activity of 71 unmedicated depressed participants to the brain activity of 88 healthy control participants. While undergoing the brain scan, the participants completed a self-appraisal task in which they were shown personal adjectives such as “lucky” and “skeptical” and then asked whether the words accurately described them.

“The way that people think about themselves is affected by depression,” Davey said. “People with depression think about themselves more negatively, they spend more time thinking about themselves, and have trouble switching between thinking about themselves and thinking about the world outside them. Our findings find some brain basis for these difficulties.”

The researchers found that the medial prefrontal cortex helped to coordinate self-appraisal processes by regulating activity in another area of the brain known as the posterior cingulate cortex. Among depressed participants, the medial prefrontal cortex had a greater influence over the posterior cingulate cortex.

MRI brain scan with highlighting indicating location of the posterior cingulate cortex. (Photo credit: Geoff B Hall)

“When a person with depression thinks about themselves, the medial prefrontal cortex — the part of the brain behind the forehead — exerts more control over other parts of the brain involved with self-appraisal than it does in people without depression,” Davey explained to PsyPost. “This part of the brain is important for directing thought, for integrating information from different sources, and switching between them. We think it helps to explain the difficulties that people with depression have in thinking about themselves, and in flexibly switching between thinking about themselves and thinking about other things.”

The study was cross-sectional, meaning that the researchers cannot make inferences about cause and effect.

“Our study shows a relationship between changes in brain connectivity and self-appraisal processes in depression,” Davey said. “It doesn’t show that these changes cause depression. We think it highlights how important it is for psychotherapy to target self-related thoughts – as most effective psychotherapies do – and we would be keen to see if these brain alterations normalise with effective treatment. We also showed that the abnormalities were even more pronounced in people with both depression and anxiety, and would be keen to explore the influence of anxiety in future studies.”

The study, “A Brain Model of Disturbed Self-Appraisal in Depression“, was also co-authored by Michael Breakspear, Jesus Pujol, and Ben J. Harrison. It was published online June 09, 2017.

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