DISSOCIATIONS AMONG THE ANXIOLYTIC EFFECTS OF SEPTAL, HIPPOCAMPAL, AND AMYGDALOID-LESIONS

Fear reactions of rats given bilateral lesions to the septum, hippocam pus, or amygdala were compared with those of rats given sham lesions, in 2 animal models of anxiety: the shock-probe burying test and the el evated plus-maze test. Septal lesions produced anxiolytic effects in b oth tests (i.e., an increase in open-arm activity and a decrease in bu rying), whereas hippocampal and amygdaloid lesions produced neither of these effects. On the other hand, hippocampal and amygdaloid lesions impaired rats' passive avoidance of the electrified shock-probe, where as septal lesions did not. These dissociations suggest that limbic str uctures such as the septum, amygdala, and hippocampus exert parallel b ut distinct control over different fear reactions.