Neurobiology of taste-recognition memory formation.

Recognition memory is the ability to assert the familiarity of things previously encountered. In the case of food, when an animal encounters a new taste, it hesitates to eat it, showing a reduced consumption—a neophobic response. However, when the new taste has no negative consequences, it becomes recognized as a safe signal, leading to an increase in its consumption (attenuation of neophobia). But if the new taste is associated with malaise, animals develop a long-lasting aversion to that taste—the taste cue becomes an aversive signal—rejecting it the next time they encounter it, being the taste the conditioned stimulus (CS) and the malaise inducing agent the unconditioned stimulus (US). This form of recognition memory is referred to as conditioned taste aversion (CTA) (Bermudez-Rattoni, 2004). Both aversive and safe taste memories depend on the neural representation of the taste that probably remains temporarily stored in several brain regions in parallel where it might be processed in either direction (safe or aversive taste memory) (Bermudez-Rattoni, 2004). This neural representation has been called the taste memory trace (TMT) (Bermudez-Rattoni, 2004). However, it still remains to be demonstrated whether the TMT has two independent components (aversive and safe), or if there is only one TMT, which could be converted into an aversive TMT when it is associated with visceral malaise.