Evidence of altered cerebral blood-flow relationships in acute phobia.

Functional cerebral guiding and integrating systems may be revealed by analyzing the covariation of regional cerebral blood flow (rCBF). Positron emission tomography (PET) was used to measure absolute rCBF in 14 volunteers with specific phobia and 6 nonphobic controls, when exposed to videos containing phobia-relevant and neutral scenes. A fear reaction and increased covariation between absolute rCBFs was observed during phobia-relevant as compared to neutral stimulation in phobics only. In controls fear was not elicited and rCBF covariation was not influenced by stimulus condition, being similar to the pattern observed in phobics during neutral stimulation. We suggest the rCBF correlative pattern during phobic fear to reflect fear-related activation of distinct neuronal pathways that involves the amygdala, the thalamus, and the striatum. We theorize that these pathways are activated also by uncontrolled emotions in diverse conditions, like posttraumatic stress disorder, panic disorder, and schizophrenia.