COMPETITION AND SUMMATION BETWEEN REWARDING EFFECTS OF SUCROSE AND LATERAL HYPOTHALAMIC-STIMULATION IN THE RAT

Rats were offered a forced choice between a train of brain stimulation that varied in strength from trial to trial and a fixed standard rewa rd. This standard reward consisted of an intraoral sucrose infusion pr esented either alone or paired with an equipreferred train of brain st imulation. Postingestional effects were minimized by opening a gastric cannula. The presence of a sucrose standard led the subjects to forgo trains of brain stimulation for which they had responded when the suc rose was absent. The strength of the brain stimulation required to bal ance the compound reward exceeded the stimulation strength required to balance a reward consisting of sucrose alone. These results imply tha t the rewarding effects of brain stimulation and intraoral sucrose can be evaluated in a common system of measurement and combined.