Increased Amygdala Activation to Angry and Contemptuous Faces in Generalized Social Phobia
Stein MB, Goldin PR, Sareen J, Zorrilla LT and Brown GG;
Commented by , 12 Dec 2002
Aim of the study
Persons with generalized social phobia (GSP) are hypersensitive to the negative reactions (such as anger or disapproval) of other people. According to recent data, the amygdala plays a major role in the processing of emotional cues. The aim of the present study was to determine whether the presentation of disorder salient stimuli (angry and contemptuous faces) elicit greater amygdala activation in patients with (GSP) than in healthy controls (HCs).
Method
The diagnosis of social phobia was determined using the Structured Clinical Interview for DSM-IV or SCID. Additional probes were used to determine the diagnosis of the generalized type of social phobia. Comorbid mood (nonbipolar) and other anxiety disorders were not excluded “if deemed of lower priority”. Subjects were also assessed for avoidant personality disorder.
Brain activation was assessed using functional magnetic resonance imaging (fMRI) based upon blood oxygen level-dependent (BOLD) response. To assess brain activation, the authors used a face emotion task. Within an MRI magnet, 15 right-handed subjects with GSP and 15 HCs viewed color photographs of 60 human facial expressions (either angry, fearful, contemptuous, happy, or nonexpressive).
Results
Subjects with GSP (72,7% also met criteria for avoidant personality disorder) showed significantly greater brain activation in several left medial temporal lobe (MTL) areas, including the left amygdala, uncus and parahippocampal gyrus, than HCs, when viewing harsh (angry, contemptuous, and fearful) facial expressions. The BOLD response was significantly greater in subjects with GSP than in HCs, when harsh expressions were contrasted with accepting or happy faces.
Discussion
Numerous studies have implicated the amygdala in the pathophysiology of anxiety and anxiety disorders, in particular regarding conditioned fear and post-traumatic stress disorder.
The findings of the current study confirm the implication of the amygdala in anxiety and anxiety disorders, and suggest a possible implication of the amygdala in the neurobiology of social phobia.
The most striking finding of the study concerns the presence of increased amygdala activation to disorder-specific stimuli (angry and contemptuous faces) in GSP. According to the authors, this is the first time that an emotion-specific effect has been found in the amygdala using fMRI.
The study presents several important limitations. In particular, it relies on a small sample of patients and includes GSP patients with various comorbid conditions, including in particular other anxiety disorders. As suggested by the authors, increased amygdala response may be a feature shared by a number of anxiety disorders and selectivity of response to particular “danger” stimuli may be what differentiates them.
In spite of these limitations, the findings from this fMRI study are highly interesting. They highlight the potential of fMRI in psychiatric research and are an important addition to the understanding of the neurobiological basis and the pathophysiologic mechanism of anxiety disorders in general, and of generalized social phobia in particular.