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Rats were permitted to ingest a novel food and a familiar food. One hour later they were x-irradiated. When they were subsequently allowed to choose between these foods, their preference for the novel food was less than that exhibited by appropriate controls.

Rats were familiarized with milk for 5 days. A few days later, experimental Ss drank sucrose solution and after 3.5-32 hr. were exposed to 50 r. of X-rays. Sham controls were not X-irradiated. Irradiated controls ate chow prior to irradiation. In a subsequent preference test, those experimental Ss irradiated 6.5 hr. or less after sucrose consumption exhibited an aversion to sucrose relative to both type of controls. In a similar experiment, rats exposed to 50, 150, or 250 r. 7 hr. after consuming sucrose solution developed greater aversion to sucrose solution with increasing radiation dose.

In 2 experiments, the effects of axon-sparing lesions of the hippocampus on performance in aversive and appetitive taste conditioning tasks were investigated. In Experiment 1, hippocampally lesioned rats showed no impairment of conditioned taste aversion learning relative to control subjects, but they did display an increased sensitivity to latent inhibition (LI). In Experiment 2, the same hippocampectomized rats acquired a conditioned taste preference but failed to show any evidence of extinction. The influence of the neurotoxic lesion on LI is in the opposite direction to the effect typically found following hippocampal damage induced by traditional methods. Accordingly, the data present challenges for most current theories of hippocampal function.