Neurological Substrates of Aggressive Behavior

Stalking attack, defensive reactions, flight, cooperative interactions be­ tween members of a species in a fight, display of the killer instinct, and predation are but some of the overt agonistic behaviors recognized among various animal species, including man. Ethologists frequently distinguish be­ tween interspecific hunting behavior, predation, which generally is used by animals to satisfy a physiologic need such as hunger, and intraspecific social aggression, or fighting behavior, which may be more related to an emotional gratification and which frequently does not result in death of the participants. Eibl-Eibesfeldt (56), however, has noted that in some instances hunting be­ havior among predators is not especially related to hunger satisfaction. It appears evident that specific neural mechanisms underlie aggressive be­ havior since an animal's pattern of activity can be changed from quiescent to savage or from savage to docile by electrical stimulation of specific brain sites. That such transformations may take place regardless of the environ­ mental milieu and that they cannot be conditioned indicate the existence of so-called innate determined patterns of agonistic behavior. On the other hand, stimulation of other brain sites may also lead to aggressive reactions which are situation-dependent and which can easily and quickly be condi­ tioned. The neural mechanisms underlying these latter patterns seem not pre­ determined, but appear dependent upon preceding, current, and predicted en­ vironmental experience. In this review the neural substrates of specific aggressive behaviors will be examined.2 Our objectives will be to define patterns of agonistic behavior, to