Functional MRI of human Pavlovian fear conditioning: patterns of activation as a function of learning

fMRI was used to study human brain activity during Pavlovian fear condition ing. Subjects were exposed to lights that either signaled painful electrica l stimulation (CS+), or that did not serve as a warning signal(CS-). Unique patterns of activation developed within anterior cingulate and visual cort ices as learning progressed. Training with the CS+ increased active tissue volume and shifted the timing of peak fMRI signal toward CS onset within th e anterior cingulate. Within the visual cortex, active tissue volume increa sed with repeated CS+ presentations, while cross-correlation between the fu nctional time course and CS- presentations decreased. This study demonstrat es plasticity of anterior cingulate and visual cortices as a function of le arning, and implicates these regions as components of a functional circuit activated in human fear conditioning. (C) 1999 Lippincott Williams a Wilkin s.