Memory Formation Different in Those With Stress-Related Psychiatric Disorders

WEDNESDAY Dec. 3, 2008 -- People with stress-related psychiatric conditions have faulty circuitry in the part of the brain that helps govern memories, a new study suggests.

For the study, researchers presented a list of word pairs to two groups of patients, those with major depression and those with other personality disorders, and a healthy control group.

The researchers then used functional magnetic resonance imaging (fMRI) to view the prefrontal cortex, an area of the brain involved in the formation of memories during traumatic events, while patients were given one word from the pair and asked to either recall or suppress their memory of the other word.

"The dorsal prefrontal cortex is hyper-activated during tasks which require suppression and retrieval of memory" in these patients, said Dr. Nivedita Agarwal, a radiology resident at the University of Udine in Italy, where the study is being conducted, and a research fellow at the Brain Imaging Center of McLean Hospital at Harvard Medical School in Boston. "Patients with major depressive, anxiety and borderline personality disorders who have undergone some kind of major trauma cannot suppress unwanted memories of the event."

The findings, to be presented Wednesday at the Radiological Society of North America annual meeting in Chicago, pose a number of questions for future research, and may lead to new treatments for people suffering from post-traumatic stress disorder (PTSD) and other stress-related mental illnesses, the researchers said.

"Are people born prone to these types of psychiatric disorders or are the chronic events the cause of later dysfunction?" asked Agarwal. "What comes first, the chicken or the egg?"

Dr. Charles Marmar, a psychiatrist and chief of mental health services at the San Francisco Veterans Affairs Medical Center, said the study was interesting but questioned its importance relative to other research.

"In the modern industrialized world with war, terrorism, traffic accidents and other terrible things that happen in the world, people are overexposed to life threats and it's not particularly helpful or adaptive to be heavily traumatized by that," said Marmar. "But this study has some significant limitations, including a small sample size, a heterogeneous patient population, and lack of information about whether the controls were trauma controls or not."

Marmar also pointed out that the brain's complexity makes drawing conclusions from such a small study impossible.

"It's definitely true that the prefrontal cortex modulates the emotional value associated with memories, but it's not necessarily true that it suppresses the actual memories," Marmar said.

Agarwal also cautioned against drawing premature conclusions from the study, but believes the research might lead to more empathy for those with mental disorders and possible future treatments.

"When patients are depressed sometimes there is a reason, and a vacation or something won't help," said Agarwal. "The next step is how can we make things better."

More information

There's more on psychiatric disorders at the U.S. National Institute of Mental Health.

Posted: December 2008


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