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Lesions to the basolateral amygdala produced permanent impairment in the ability of rats to learn a taste aversion. When lesions were administered after rats had already learned an aversion, there was complete loss of the aversion. Rats with amygdala lesions also had a diminished neophobic response when presented with a novel solution and showed a more generalized aversion to water after a sucrose-sickness trial. Whether a solution was novel or familiar affected the learning of an aversion for controls more than it did for rats with amygdala lesions. Rats with amygdala damage also showed less sodium appetite than normals in response to DOCA injections. These results were interpreted as indicating that rats with amygdala lesions have deficits in recognizing the significance of stimuli.

Rats, reared on water, were given saccharin and then made sick with a single LiCl injection after various intervals. Similarly, animals reared on saccharin were made sick with LiCl at various times after drinking water. In both conditions, rats learned to avoid drinking the fluid which preceded sickness and the amount of aversion was a function of the sickness delaj time. Similar tests with 43° C. water as the OS also produced learned aversions, but the longest effective sickness delay time with the temperature cue was less than 1 hr. compared to several hours with the taste cues. In a third experiment, rats, experienced with water and saccharin, learned specifically to avoid the fluid which they had drunk preceding their sickness, even with sickness delay times of several hours.

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