A complex nervous system mechanism is involved in the acquisition of CTA
[39][40]. Animal models provide critical data to understand the neuroanatomy and neurobiology of taste learning and memory. The neural network of taste aversion learning and memory includes the nucleus of the solitary tract (NTS), the posteromedial pontine parabrachial nucleus, the lateral hypothalamus, the bed nucleus of the stria terminalis, the amygdala and the ventroposteromedial and lateral thalamus. The superior cortical level of processing has been described in the gustatory insular cortex region. The functional connectivity between the parabrachial nucleus and the gustatory insular cortex is selectively involved in the acquisition of CTA but not in the formation of safe taste memories
[41]. These pathways and the vagal system involved in the processing of visceral malaise are necessary for the acquisition of CTA and taste aversion memory
[7][8][9][11]. Moreover, the role of other brain structures in the neurobiology of CTA, such as the medial prefrontal cortex and the nucleus accumbens, is being elucidated at present
[42], together with the functions of the piriform
[43] and perirhinal
[44] cortices in taste recognition. The neural system of CTA involves the activity of this brain and brainstem network, but the specific functions of each component are not fully understood. Although the CTA mechanisms of the gustatory insular cortex and parabrachial nucleus are well described, the involvement of the amygdala and its nuclei in specific processes of taste aversion learning and memory is not fully known
[45][46][47]. Animal lesion studies have pointed to the central and basolateral nuclei of the amygdala as the amygdaloid nuclei with specific functions in taste aversion learning and memory
[48]. However, the basolateral amygdala seems to be the main nucleus involved in the acquisition of CTA
[47], probably modulating the magnitude of taste aversion
[49][50]. A possible mechanism by which basolateral amygdala can modulate the intensity of CTA is through the neophobia phenomenon, considering that this nucleus is implicated in the perception of novelty of taste stimuli. The correct processing of novelty is one of the mechanisms affecting the magnitude of CTA
[51]. In addition to lesion studies, other methods and approaches have also pointed to the basolateral amygdala as a selective amygdaloid nucleus mediating the acquisition of CTA. By two-photon calcium imaging it has been revealed that a CTA-dependent neuronal activation of specific neurons of the insular cortex that project to the basolateral amygdala
[52], and chemical activation of the insular cortex-basolateral amygdala projection by Clozapine-
N-oxide after taste exposure, can induce aversive taste memory in mice
[53]. Thus, the function of the basolateral amygdala on CTA might be controlled by afferent axons from the gustatory insular cortex
[51]. Moreover, molecular studies have supported the relevance of this cortico-amygdaloid projection for the formation of CTA
[54][55]. It can be concluded that specific connections between the gustatory insular cortex and the basolateral complex of the amygdala
[47][55][56], and between the amygdala and the brainstem nuclei involved in CTA
[9][45][46], could be recruited to influence the intensity of acquired taste aversions.