Cerebral blood flow during anticipation of public speaking in social phobia: a PET study

Background The aim was to examine the neural correlates of anxiety elicited by the anticipation of public speaking in individuals with social phobia. Methods Positron emission tomography and 15O-water was used to measure regional cerebral blood flow in subjects with DSM-IV defined social phobia during anxiety anticipation. Heart rate and subjective anxiety were also recorded. While being scanned, subjects were speaking alone either before or after speaking in public. To evaluate anticipatory anxiety we compared individuals speaking alone before they were speaking in front of an audience with those who did the reverse. Results Heart rate and subjective anxiety measures confirmed anticipatory anxiety in social phobics who performed their private speech before their public. This was accompanied by enhanced cerebral blood flow in the right dorsolateral prefrontal cortex, left inferior temporal cortex, and in the left amygdaloid-hippocampal region. Brain blood flow was lower in the left temporal pole and bilaterally in the cerebellum in the anticipation group. Conclusions Brain regions with altered perfusion presumably reflect changes in neural activity associated with worry about anticipated public performance. We speculate that anticipatory anxiety in social phobics originates in an affect sensitive fear network encompassing the amygdaloid-hippocampal region, prefrontal, and temporal areas.