A network of emotion-regulating brain regions implicated in the pathological worry that can grip patients with anxiety disorders may also be useful for predicting the benefits of treatment.
A new study reports that high levels of brain activity in the amygdala reflect patients' hypersensitivity to anticipation of adverse events. At the same time, high activity in a regulatory region known as the anterior cingulate cortex (ACC) is associated with a positive clinical response to a common antidepressant medication.
Psychologists know that for individuals with anxiety disorders, the anticipation of a bad outcome can be worse than the outcome itself. To study how the brain responds to anticipation, researchers used functional magnetic resonance imaging (fMRI) to examine patients with generalized anxiety disorder (GAD) as they viewed a set of negative and neutral images. Patients were shown pre-image cues several seconds before each picture so they would know what to expect: a circle before a neutral image and a minus sign before an aversive image.
While GAD patients showed no difference in brain activation— compared to healthy subjects—in response to the aversive or neutral pictures themselves, they displayed unusually high levels of amygdala activity in response to both anticipatory cues. The response suggests that the patients are hypersensitive to the anticipation of any stimuli, even those they are told will not be negative.
The researchers believe the high levels of amygdala activity seen in GAD patients reflects an indiscriminate and disproportionately large response to the idea that something negative might happen in the future, even in a laboratory setting where they know nothing bad will actually occur. It suggests that there are differences in anticipatory brain processing in these individuals.
The patterns of brain activity also appear to hold predictive power for how patients will respond to treatment for their anxiety. After their brain scans, the GAD patients in the study received an eight-week course of treatment with venlafaxine (Effexor), a common antidepressant. Clinical improvement on the medication was associated with higher levels of pre-treatment brain activity in the ACC in anticipation of both aversive and neutral stimuli. The ACC is a regulatory brain region important for modulating emotional responses. Activity in the same area has been shown to predict clinical outcome in patients with depression.
Nitschke, J.B., Sarinopoulos, I., Oathes, D.J., Johnstone, T., Whalen, P.J., Davidson, R.J., & Kalin, N.H. (2009, January 2). Anticipatory activation in the amygdala and anterior cingulate in generalized anxiety disorder and prediction of treatment response. American Journal of Psychiatry [Article published online before print]. Retrieved February 5, 2009, from the journal website at http://ajp.psychiatryonline.org/cgi/content/abstract/appi.ajp.-2008.07101682v1g. The full article can be accessed online for $15.
University of Wisconsin–Madison (2009, January 2). Expectant brains help predict anxiety treatment success. Retrieved February 5, 2009, from http://www.news.wisc.edu/releases/14982