Hypothalamic influences on sensory reinforcement.

Rats were tested in a darkened chamber containing two levers, one of which turned on a dim light when depressed. Rats receiving non-contingent electrical stimulation of the lateral hypothalamus made many more lever presses than did unstimulated controls and made more presses on the light producing lever than on the inactive one. Pretests had shown that the electrical stimulation elicited consummatory behavior in the presence of appropriate goal objects. Dynamic hyperphagic rats maintained on a restricted diet made more total responses early in testing than did their controls which also received the same restricted diet. They also preferred the light producing lever, but not reliably more than did their controls. Static hyperphagic rats made fewer total responses than did their controls, both groups receiving food ad lib. Neither group showed any preference between the two levers.