Conditioned taste aversions

Abstract

When one becomes ill after consuming a meal, there is a propensity to target a particular taste as the cause of the illness. The qualities of the taste most likely targeted include more novel, less preferred, and higher protein content. This association between a particular taste and illness is a form of learning that is termed conditioned taste aversion (CTA). A consequence of the learned association is that the taste will become aversive. When experiencing the taste again, individuals will show aversive reactions such as expressions of loathing, will experience mimicked illness sensations such as nausea, and subsequently, will avoid further exposure to the taste. The ability to acquire CTA occurs across species and across ages within a species. In the rat animal model, however, age differences exist in the capability of acquiring CTAs when increasingly longer intervals are imposed between consumption of a novel sweet solution and onset of illness. Pups have a decreased ability compared to young adults while aged rats have an increased ability. Evidence suggests that the failure of pups to acquire CTA at longer intervals is due to an immature retrieval mechanism and the facilitated ability of aged rats is due to a compromised clock mechanism that tracks the passage of time. Learned taste-illness association serves the critical function of informing individuals of the toxic nature of certain foods, thus preventing further illness and potentially death. Additionally, it contributes to the hypophagia observed during cancer chemotherapy and may contribute to the hypophagia found while suffering from bacterial infection, chronic medical conditions such as cancer, and restrictive food intake disorders such as anorexia nervosa.

Behavior and Fos activation reveal that male and female rats differentially assess affective valence during CTA learning and expression

“…CTA is a classical conditioning paradigm which pairs a palatable substance with an aversive visceral experience, such as the emetic agent lithium chloride (LiCl), producing an aversion to the substance at subsequent exposure. Unlike many other classical conditioning paradigms, in which an aversive stimulus is paired with a neutral cue, the use of a palatable substance in CTA requires the animal to process the affective valence of the reward versus the aversion [14][15][16]. This provides an opportunity to understand neural processes by which this decision-making occurs.…”

Learning of food preferences: mechanisms and implications for obesity & metabolic diseases

“…If the food contains toxins or poorly digested nutrients (e.g., lactose) that produced gastrointestinal distress, animals rapidly learn to avoid its flavor. Conditioned flavor aversions are well documented as reviewed elsewhere [ 27 , 72 , 73 ]. Of interest here are flavors that are associated with positive reinforcing consequences [ 27 ].…”

What can we teach Lymnaea and what can Lymnaea teach us?

“…Because this behaviour can be conditioned by internal cues that occur after ingestion of an aversive substance [e.g. the Garcia effect (Garcia, Hankins & Rusiniak, 1974; Garcia et al ., 1985)], observing the aversive reaction of a peer (Chambers, 2018), or a bitter taste (Sugai et al ., 2006), it is often termed conditioned taste aversion (CTA).…”