No abstract

Male mating behavior, biting attack, defensive threat, eating, grooming, yawning, investigating, and escape-like activity were produced by electrical stimulation of differentiated zones in hypothalamus and preoptic area of oppossums. Close anatomical correspondence with similar mechanisms in higher species suggested considerable phylogenetic continuity from early mammalian levels. Responses involving environmental goals were not performed without the objects, indicating that they were facilitated rather than directly elicited by the stimulation. The interelectrode variability in the completeness of complex response patterns suggested that each zone sends divergent facilitatory output to separate sensory-motor mechanisms for different response elements. The performance of the mating pattern without intromission was an effective reward in a maze.

No abstract

Hypothalamic stimulation caused 9 normally nonaggressive cats to make predatory attacks on rats. During stimulation, all learned a Y maze to obtain a rat that they could attack. When stimulation was omitted, performance of the learned habit deteriorated and there were no attacks. When the stimulation was turned on during eating of cat food, the cats switched to attack on a nearby rat, indicating that the attack was not due to hunger. It was concluded that the performance of the attack was rewarding, and that the central readiness for attack elicited by the stimulation possessed motivational and cue properties salient in the evocation of the learned responses leading to prey.

When a strong readiness to gnaw was elicited by hypothalamio stimulation in rats, gnawable objects acted as rewards to produce learning of position and black-white discrimination habits in a Y maze. Control Ss given stimulation that did not evoke gnawing did not learn. Experimental Ss did not gnaw without stimulation or when the object was armored with sheet metal. If stimulation was turned on while experimental Ss were eating powdered food, they ceased eating and gnawed on a board, indicating that gnawing was not due to hunger or to nonspecific activation of dominant responses. Functions of reward effects.exerted by innate responses and relation of innate response mechanisms to basic drives are discussed.