Ethological models in research into the neural mechanisms of short-term memory

Rats are protected against intake of toxic diets by specific evolutionary prepared behavioral adaptations. Intake of potentially dangerous novel food is reduced by neophobia. The taste signal is stored for several hours in a short-term memory file from which it gradually emerges in form of a permanent gustatory engram labeled as safe, when there are no adverse effects of feeding, or as aversive, when visceral symptoms of poisoning appear in the critical post-ingestion interval. The experimental evidence reviewed indicates that positive labeling (manifested by attenuation of neophobia) requires intact higher brain functions whereas the aversive experience (manifested by conditioned taste aversion) is recorded even under deep coma. The biological significance of the different neural mechanisms underlying the above forms of gustatory-visceral associations is discussed.