Effects of ventromedial hypothalamic lesions on hunger-motivated behavior in rats.

Previous studies show that lesions of the ventromedial hypothalamus (VMH) paradoxically increase food intake and decrease hunger motivation in the rat. In a series of experiments designed to examine this paradox, independent groups of VMH-lesioned, female hooded rats (N = 48) were tested on a VI schedule or were run in a straight alley to a food reward. Rate of food ingestion was also measured for all Ss. Performance of the VMH and control groups was compared at identical deprivation conditions defined in terms of preoperative base-line weights (80, 90, 100, and 110%). All test measures showed a significantly higher level of performance for VMH-lesioned Ss at the least severe deprivation conditions. Results suggest that the previously reported VMH paradox originated, in part, from inappropriate testing procedures and between-group comparisons. (20 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)