fMRI could detect source of stress-related suppressed memories

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CHICAGO—Functional MRI (fMRI) could determine that the circuitry in the area of the brain responsible for suppressing memory is dysfunctional in patients suffering from stress-related psychiatric disorders, according to a study presented today at the 94th annual meeting of the Radiological Society of North America (RSNA).

“For patients with major depression and other stress-related disorders, traumatic memories are a source of anxiety,” said Nivedita Agarwal, MD, a radiology resident at the University of Udine in Italy and research fellow at the Brain Imaging Center of McLean Hospital, Department of Psychiatry at Harvard Medical School in Boston.

Agarwal and colleagues used brain fMRI to explore alterations in the neural circuitry that links the prefrontal cortex to the hippocampus, while study participants performed a memory task. Participants included 11 patients with major depression, 13 with generalized anxiety disorder, nine with panic attack disorders, five with borderline personality disorder and 21 healthy individuals.

She reported that all patients reported suffering varying degrees of stressful traumatic events, such as sexual or physical abuse, difficult relationships or a type of bullying or harassment at some point in their lives.

After reviewing a list of neutral word pairs, each participant underwent fMRI. During imaging, they were presented with one of the words and asked to either recall or to suppress the memory of its associated word.

The fMRI images revealed that the prefrontal cortex, which controls the suppression and retrieval of memories processed by the hippocampus, showed abnormal activation in the patients with stress-related disorders compared to the healthy controls, according to Agarwal. During the memory suppression phase of the test, patients with stress-related disorders showed greater activation in the hippocampus, suggesting that insufficient activation of the prefrontal cortex could be the basis for inadequate suppression of unwanted traumatic memories stored in the hippocampus.

“These data suggest that the mechanism for memory suppression is dysfunctional in patients with stress-related disorders primarily because of an alteration of the prefrontal cortex,” Agarwal said. "These patients often complain of poor memory, which might in part be attributed to this altered circuitry," she added.

According to Agarwal, fMRI is an important tool in understanding the neurobiological basis of psychiatric disorders and in identifying imaging markers to psychiatric disease, helping clinicians target specific parts of the brain for treatment.