fMRI links traumatic flashbacks to brain malfunction

December 3, 2008

For victims of psychological trauma, the challenge of suppressing painful memories may be rooted in the wiring of the brain, an ongoing study revealed at the RSNA conference Wednesday.

For victims of psychological trauma, the challenge of suppressing painful memories may be rooted in the wiring of the brain, an ongoing study revealed at the RSNA conference Wednesday.

"These patients, they just become hyper-vigilant, hypersensitive to these events, and they are not capable of processing them, so they have flashbacks," said Dr. Nivedita Agarwal, a radiology resident at the University of Udine in Italy who presented the study.

Her task is to figure out what makes it so hard for patients to forget.

Using fMRI, Agarwal and her colleagues examined activity in two areas of the brain: the hippocampus, which stores memories, and the prefrontal cortex, which enables the mind to retrieve or repress them.

They discovered that patients with stress-related disorders reported much lower activity in the prefrontal cortex when trying to suppress memories than their healthy counterparts.

The group of 39 patients encompassed victims of major depressive disorder, borderline personality disorder, panic disorder, and generalized anxiety disorder. Agarwal said all of these disorders are characterized by repeated traumatic events that can range from accidents to physical or sexual abuse.

Argarwal's team used the Anderson test, also known as the "think/no think paradigm" to detect memory activity in the brain.

During the first phase of the test, participants, including a healthy control group, were presented with 36 neutral pairs of words, such as "monkey" and "banana." In the second phase, participants were shown one word in either red or green. If the word "monkey" appeared in green, they were supposed to remember "banana;" If it appeared in red, they were supposed to suppress it.

The patient group registered more general brain activity in both retrieval and suppression, suggesting that victims of psychological disorders have to exert a greater effort than healthy people to accomplish the same memory tasks. But during the suppression phase, patients showed much less activity in the prefrontal cortex, a sign that at least one part of the brain might not be functioning properly.

Agarwal pointed out that the study did not eliminate other neurological problems to the prefrontal cortex.

"The idea behind the study was to test if there was a problem in the prefrontal cortex and the hippocampus circuitry," she said. "It might be that there are other problems in these patients."