Medial hypothalamic and medial accumbens lesions which induce mouse killing enhance biting and attacks on inanimate objects

Abstract

The response to a series of objects by rats with lesions of the medial hypothalamus or medial accumbens was compared to that of spontaneous killing rats and sham-lesioned nonkillers. When exposed sequentially to a piece of wood, a wad of cotton, or a freshly killed mouse, there were no differences in the intensity of the initial response toward the stimulus object by spontaneous mouse killing rats and lesioned animals that were later shown to kill mice. However, lesioned animals did spend more time biting these objects and were more likely than spontaneous killers to attack the objects if they were moved about by the experimenter. When allowed to kill mice, there were no differences in the intensity of the attack by spontaneous and lesion-induced killers but again the lesioned animals bit the prey more following the kill and were more likely to attack the dead prey when it was moved by the experimenter. Sham-lesioned nonkillers spent less time biting the stimulus objects than spontaneous killers and never attacked the objects when they were moved by the experimenter. It is argued that the killing of lesioned animals is homologous to that of spontaneous killers but that the lesioned animals exhibit most components of the predatory behavior to an exaggerated degree.