Aggressive Behavior Evoked by Radio Stimulation in Monkey Colonies

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Abstract
Macaca mulatta with multilead electrodes permanently implanted in the brain were electrically stimulated, either under restraint, or by radio while moving freely as part of a colony, in which case individual and social behavior were recorded, analyzed, and quantified with the aid of time-lapse photography. Some cerebral radio stimulations evoked complex sequences of well organized responses. Increase in running and in offensive behavior was produced by excitation of midline thalamus, while even faster running without changes in aggressiveness was produced by stimulation of the fimbria of the fornix. Conditioning was absent in the first case, but it was easily established in the latter. Increase in aggressive behavior was also produced by stimulation of Forel's field, the nucleus ventralis posterior lateralis of the thalamus, and the central gray matter. Increase in aggressiveness was oriented by the animal according to past experience, likes and dislikes, and was adapted to the changing strategies of its opponent, indicating an excellent processing of sensory information, and demonstrating that brain stimulation had induced a “drive” and not a stereotyped motor response. As a working hypothesis it is proposed that cerebral mechanisms for perception of pain and for aggressive behavior have different anatomical and physiological systems closely interrelated by use, disuse, and conditioning.