Effects of insular cortex lesions on conditioned taste aversion and latent inhibition in the rat

Abstract

The present study tested the hypothesis that lesions of the insular cortex of the rat retard the acquisition of conditioned taste aversions (CTAs) because of an impairment in the detection of the novelty of taste stimuli. Demonstrating the expected latent inhibition effect, nonlesioned control subjects acquired CTAs more rapidly when the conditioned stimulus (0.15% sodium saccharin) was novel rather than familiar (achieved by pre-exposure to the to-be-conditioned taste cue). However, rats with insular cortex lesions acquired taste aversions at the same slow rate regardless of whether the saccharin was novel or familiar. The pattern of behavioural deficits obtained cannot be interpreted as disruptions of taste detection or stimulus intensity, but is consistent with the view that insular cortex lesions disrupt taste neophobia, a dysfunction that consequently retards CTA acquisition because of a latent inhibition-like effect.

Preexposure to salty and sour taste enhances conditioned taste aversion to novel sucrose

“…Previous experience with tastes other than the CS might enhance attention to the newly experienced taste by increasing its novelty (Kutlu and Schmajuk 2012). This suggestion jibes well with latent inhibition studies, wherein exposure to the CS causes a reduction in the conditioning effect (Lubow and Moore 1959;Lubow 1973;McLaren and Mackintosh 2002), a reduction that has been suggested to reflect the loss of novelty (Roman and Reilly 2007;Reilly and Schachtman 2009). It is possible that the learned association of a "safe outcome" (or "no outcome") with the diverse taste array reduces the associability of those specific tastes, thereby increasing attention to the novel CS as the source of the malaise (in turn increasing the magnitude of the conditioning).…”

NMDA receptors in the basolateral amygdala and gustatory neophobia

“…Experiments from our laboratory show that neurotoxic lesions of the insular cortex disrupt the acquisition of conditioned taste aversions (CTAs), particularly when the taste stimulus is novel (Roman, Nebieridze, Sastre, & Reilly, 2006;Roman & Reilly, 2007). These results suggest that the insular cortex has a role in gustatory neophobia.…”

The Insular Cortex and the Amygdala: Shared Functions and Interactions

“…IC lesions induce a consistent decrease in taste neophobia when the novel taste is presented in a familiar environment [146,[148][149][150][151][152]. As most studies so far have focused on taste memory, pharmacological interventions into the IC are performed only after taste presentation and very few -if any -pharmacological studies have investigated the neurotransmitters involved in taste neophobia per se.…”

“…IC lesions appear to produce no effects on animals' capacity to attain taste familiarity [151], but several reports document a role for the IC in taste familiarity learning as a result of pharmacological manipulations [153,154], showing that taste familiarity requires cholinergic activity in the IC [155,156] but that it is independent of NMDA and AMPA channel activity [157][158][159][160]. Perhaps this dichotomy can be explained either by compensation from other areas after IC lesions or, given the role of neophobia discussed above, it is possible that IC output per se may modulate familiarity.…”

“…The basolateral complex of the amygdala (BLA; consisting of the lateral, basal and accessory basal nuclei) is critical for mediating the effects of stress on memory in several types of learning [212]. BLA also interacts with the IC in regulating taste neophobia [151,20,213] and, as mentioned earlier, CTA.…”