Worry is considered a key feature of generalized anxiety disorder (GAD), whose neural correlates are poorly understood. It is not known whether the brain regions involved in pathological worry are similar to those involved in worry-like mental activity in normal subjects or whether brain areas associated with worry are the same for different triggers such as verbal stimuli or faces. This study was designed to clarify these issues.
Eight subjects with GAD and 12 normal controls underwent functional magnetic resonance imaging (fMRI) mood induction paradigms based on spoken sentences or faces. Sentences were either neutral or designed to induce worry. Faces conveyed a sad or a neutral mood and subjects were instructed to empathize with those moods.
We found that the anterior cingulate and dorsal medial prefrontal cortex [Brodmann area (BA) 32/23 and BA 10/11] were associated with worry triggered by sentences in both subjects with GAD and normal controls. However, GAD subjects showed a persistent activation of these areas even during resting state scans that followed the worrying phase, activation that correlated with scores on the Penn State Worry Questionnaire (PSWQ). This region was activated during the empathy experiment for sad faces.
The results show that worry in normal subjects and in subjects with GAD is based on activation of the medial prefrontal and anterior cingulate regions, known to be involved in mentalization and introspective thinking. A dysregulation of the activity of this region and its circuitry may underpin the inability of GAD patients to stop worrying.
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