Relative salience of saccharin and quinine in long-delay taste aversion learning

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In Expt I, 82 rats were subjected to toxicosis (cyclophosphamide injection), or saline injection, immediately or six hr after exposure to either 1 g/liter sodium saccharin, 10 −4 M quinine hydrochloride or water. As measured by resistance to extinction, both saccharin and quinine were discriminatively salient following immediate toxicosis, but only the quinine cue was salient following a six hr delay. In Expt II, 56 rats were used to repeat the previous delay experiment using a higher concentration of saccharin (1.5 g/liter) and a lower concentration of quinine (5 × 10 −5 ), and both cues were discriminatively salient. These results provide context for previous studies showing a loss of salience for 1 g/liter saccharin and for 5 × 10 −5 M quinine following immediate toxicosis in rats lacking gustatory neocortex. It is suggested that the salience dimension disrupted by both procedures, gustatory neocortex ablation and long CS-US delay, is either stimulus intensity or novelty.