Clinical and Research News
Different Brain Regions Activated In Impulsive Aggression
Psychiatric News
Volume 38 Number 2 page 29-48

Patients with personality disorder often react impulsively and aggressively to interpersonal emotional cues, such as conflict or perceived disrespect, according to Antonia New, M.D., an assistant professor of psychiatry at Mount Sinai School of Medicine/Bronx VA Medical Center.

A brain imaging study by New and a team of researchers at the two institutions suggests that the trait of impulsive aggression may be due to impaired brain regions that normally inhibit aggressive responses to external stimuli.

New and psychiatric researcher and colleague Larry Siever, M.D., presented the results separately at a conference last month in Bethesda, Md., on borderline personality disorder organized by the Treatment Advancements and Research Association for Personality Disorder. The study was published in the July 2002 Archives of General Psychiatry.

"Our brain imaging study shows that personality disordered patients with impulsive aggression did not activate normal inhibitory regions of the brain in response to a serotonergic stimulus. This may be one of the reasons why patients experience such great difficulty in controlling their tempers," said New in an interview with Psychiatric News.

The researchers used positron emission tomography (PET) to examine the response of brain regions to a serotonergic probe (meta-chlorophenylpiperazine, or m-CPP) in eight normal controls and 13 patients with impulsive aggression in personality disorder.

The results showed significant differences in the brain regions activated by m-CPP between patients and normal controls. There was a significantly greater response in the anterior cingulate gyrus and the medial orbital frontal cortex in normal controls. Patients, by contrast, experienced a significantly greater response in the posterior cingulate gyrus and the lateral orbital frontal cortex, said New.

"Understanding the mechanism underlying this disinhibited aggression provides us an opportunity to detect the effects of treatment on the brain mechanism involved in impulsive aggression," said New.

"Our next step is to study which subcortical brain regions are activated in response to a provocation whether by making patients angry or giving them a serotonergic agent. Our hypothesis is that the hypothalamus may be involved because animal studies have shown that electrical stimulation of this limbic region leads to aggressive behavior." ▪

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