Researchers at the NewYork-Presbyterian Hospital/Weill Cornell Medical Center in New York City have shed new light on a serious psychiatric condition - Borderline Personality Disorder.
Using new approaches, researchers have gained a view of activity in key brain areas associated with a core difficulty in patients with such an illness.
"It's early days yet, but the work is pinpointing functional differences in the neurobiology of healthy people versus individuals with the disorder as they attempt to control their behaviour in a negative emotional context. Such initial insights can help provide a foundation for better, more targeted therapies down the line," Dr. David A. Silbersweig, lead researcher, said.
"In this study, our collaborative team looked specifically at the nexus between negative emotions and impulsivity-the tendency of people with borderline personality disorder to 'act out' destructively in the presence of anger," Dr. Silbersweig said.
"Other studies have looked at either negative emotional states or this type of behavioural disinhibition. The two are closely connected, and we wanted to find out why. We therefore focused our experiments on the interaction between negative emotional states and behavioural inhibition," he added.
The research team developed advanced brain-scanning technologies, which made it possible to detect the brain areas of interest with greater sensitivity.
"Previous work by our group and others had suggested that an area at the base of the brain within the ventromedial prefrontal cortex was key to people's ability to restrain behaviours in the presence of emotion," Dr. Silbersweig said. Unfortunately, tracking activity in this brain region has been extremely difficult using functional MRI (fMRI).
"Due to its particular location, you get a lot of signal loss," Dr. Silbersweig said.
However, the research team used a special fMRI activation probe to eliminate much of that interference. This paved the way for the study, which included 16 patients with borderline personality disorder and 14 healthy controls.
Researchers also used a tailored fMRI neuropsychological approach to observe activity in the subjects' ventromedial prefrontal cortex as they performed what behavioural neuroscience researchers call 'go/no go' tests.
These tests require participants to press or withhold from pressing a button whenever they receive particular visual cues. In a twist from the usual approach, the performance of the task with negative words was contrasted with the performance of the task when using neutral words, to reveal how negative emotions affect the participants' ability to perform the task.
It was found that negative emotional words caused participants with borderline personality disorder to have more difficulty with the task at hand and act more impulsively-ignoring visual cues to stop as they repeatedly pressed the button.
"We confirmed that discrete parts of the ventromedial prefrontal cortex-the subgenual anterior cingulate cortex and the medial orbitofrontal cortex areas-were relatively less active in patients versus controls. These areas are thought to be key to facilitating behavioural inhibition under emotional circumstances, so if they are underperforming that could contribute to the disinhibition one so often sees with borderline personality disorder," Dr. Silbersweig said.
During the same time, researchers looked at heightened levels of activation during the tests in other areas of the patients' brains, including the amygdala, a locus for emotions such as anger and fear, and some of the brain's other limbic regions, which are linked to emotional processing.
"In the frontal region and the amygdala, the degree to which the brain aberrations occurred was closely correlated to the degree with which patients with borderline personality disorder had clinical difficulty controlling their behaviour, or had difficulty with negative emotion, respectively," Dr. Silbersweig said.
The new study sheds light not only on borderline personality disorder, but on the mechanisms healthy individuals rely on to curb their tempers in the face of strong emotion.
The findings are featured in this month's issue of the American Journal of Psychiatry.