FIG. 1. Effect of bilateral lesions of the ventromedial tegmentum in five rats upon predation, offense, and defense behaviors. Lesions are illustrated at their maximal extent on plates drawn from the stereotaxic atlas of Paxinos and Watson [17]. The anterior levels of the plates are given for reference only; the lesions are illustrated in terms of the actual brain structures where they were located. Predation is measured in terms of latency to kill, and offense is measured in terms of an "offense score" (see text for details). Defense is measured only at the conclusion of other behavioral testing and is quantified in terms of the percent of trials with boxing at each shock intensity presented on a titration schedule [8]. Open circles in predation data indicate the latency to attack the mouse on trials when no kill was achieved.