Effects of lesions of the gustatory neocortex on taste aversion learning in the rat.

Abstract

Normal rats and rats with lesions of the gustatory neocortex (GN) were compared for their ability to learn aversions to taste cues paired with toxicosis. When the taste presentation was followed immediately by toxicosis, normal rats and rats with lesions of the posterior (visual) neocortex learned aversions to sucrose, NaCl, quinine hydrochloride and HCl solutions. Rats with GN lesions learned aversions to all solutions except sucrose. In preference tests, all solutions were discriminable from water by both normal rats and rats with GN lesions. Under conditions in which a 6 h delay separated taste presentation and toxicosis, normal rats again learned specific aversions to all 4 solutions, but rats with GN lesions failed to learn specific aversions to sucrose, NaCl and HCl solutions. The ability of rats with GN lesions to learn aversions to sucrose and quinine depended on stimulus concentration. The data could be accounted for by postulating a change in the threshold for taste-illness associations following GN lesions.