Interactions between aversive and rewarding effects of hypothalamic stimulations

Interactions between aversive and rewarding effects of brain stimulations were studied by assessing the variation of both escape and approach responses induced in a shuttle box by applying electrical stimulations of various intensities simultaneously to a medial hypothalamic (MH) site and to a lateral hypothalamic (LH) site. The results obtained show that: (1) LH stimulation produces two effects whose relative strengths appear to depend on both the location of the stimulation site and the intensity applied: (a) a suppressant effect correlated with the rewarding effect, which reduces MH escape responding; and (b) an enhancing effect correlated with the aversive effect, which increases MH escape responding. (2) MH stimulation similarly produces two effects whose relative strengths vary with both the location of the stimulation site and the intensity applied: (a) an enhancing effect which increases LH approach responding and (b) a suppressant effect which decreases LH approach responding. (3) The above-mentioned effects occur irrespective of whether the two stimulation sites (MH and LH) are ipsi- or contralateral to each other. These results suggest that the effects of LH stimulation on MH induced escape as well as those of MH stimulation on LH induced approach are related to the affective (aversive, rewarding) properties of the stimulation.