Taste Aversion Learning as a Tool for the Study of Hippocampal and Non-Hippocampal Brain Memory Circuits Regulating Diet Selection

Abstract

Diet selection is the result of different learning experiences that accumulate throughout the life of the organism. The acquisition of aversions to the taste of food followed by mild or severe visceral negative effects plays an important role in food selection. Current knowledge on the role of the critical brain areas (parabrachial area, insular cortex and amygdala) involved in the basic associative neural circuit of taste aversion learning is reviewed. In turn, as shown by a variety of learning phenomena, the development of new aversions to the taste of different types of food is profoundly modulated by the memory of previous learning experiences with the same or different tastes. Some of these phenomena may depend on memory brain systems independent of the basic circuit for taste aversion learning. This seems to be the case for contextual effects and conditioned blocking that depend on the hippocampal integrity. Experimental evidence on the neural basis of complex learning phenomena in taste aversion learning is reviewed. Thus, understanding the way in which taste aversion learning regulates diet selection in daily life requires the study of interactions between hippocampal and non-hippocampal dependent memory systems. Taste aversion learning is proposed as a useful behavioral tool in the investigation of different brain circuits that are critical for food selection.

Peculiar modulation of taste aversion learning by the time of day in developing rats

“…The authors attributed the delayed onset of latent inhibition to immaturity of the hippocampal system, since fornix transections performed in preweanling rats disrupted the emergence of latent inhibition at 32 days of age. However, at present, there is no evidence for a critical hippocampal involvement in latent inhibition of CTA (for reviews see Buhusi, Gray, & Schmajuk, 1998;Gallo, Ballesteros, Molero, & Morón, 1999). Lesion studies in adult rats showed no effect (Gallo & Cándido, 1995) or enhancement of latent inhibition (Purves, Bonardi, & Hall, 1995;Reilly, Harley, & Revusky, 1993).…”

Amygdala and Taste Learning

“…First, CTA can be acquired with a single pairing between the taste and the visceral discomfort [6,13,[22][23][24][25]. Second, conditioned taste aversion is an example of a biological predisposition to associate certain stimuli more easily.…”

“…These nuclei have complex connections with other structures; therefore it is thought that the activity of the amygdala is relevant in the modulation of some types of learning and memory [4]. In particular, the amygdala appears to participate in several complex processes underlying taste learning [5][6][7][8][9][10][11].…”

Taste learning in rodents: Compounds and individual taste cues recognition

“…A critical feature adding complexity to taste sensation is the dynamic nature of the gustatory system, as it is modified by learning, even at the lower brainstem level (Yamamoto & Yasoshima 2007). Moreover, in spite of a general misconception about the low cognitive level of taste memory, it shows complex learning phenomena dependent on the hippocampal system (Gallo et al 1999), and it shares molecular mechanisms with other complex types of memories (Shema et al 2007).…”

“…First, in conditioned blocking, previous training with an individual member of a compound modulates learning about another member of the compound. Thus, a previously learned aversion or preference to an individual taste A retards the acquisition of a new learned response to a different taste B if the later is presented in a compound AB (Balleine et al 2005; Gallo et al 1999). The blocking phenomenon would not appear if the compound had been sensed as singular and the individual basic components had not been recognized by the animals.…”