title: Role of the insular cortex in taste familiarity.
abstract: Determining the role of the main gustatory cortical area within the insular cortex (IC), in conditioned taste aversion (CTA) has been elusive due to effective compensatory mechanisms that allow animals to learn in spite of lacking IC. IC lesions performed before CTA training induces mild if any memory impairments, while IC lesions done weeks after CTA produce amnesia. IC lesions before taste presentation have also been shown not to affect taste familiarity learning (attenuation of neophobia). This lack of effect could be either explained by compensation from other brain areas or by a lack of involvement of the IC in taste familiarity. To assess this issue, rats were bilaterally IC lesioned with ibotenic acid (200-300 nl.; 15 mg/ml) one week before or after taste familiarity, using either a preferred (0.1%) or a non-preferred (0.5%) saccharin solution. Rats lesioned before familiarity showed a decrease in neophobia to both solutions but no difference in their familiarity curve or their slope. When animals were familiarized and then IC lesioned, both IC lesioned groups treated the solutions as familiar, showing no differences from sham animals in their retention of familiarity. However, both lesioned groups showed increased latent inhibition (or impaired CTA) when CTA trained after repeated pre-exposures. The role of the IC in familiarity was also assessed using temporary inactivation of the IC, using bilateral micro-infusions of sodium channel blocker bupivacaine before each of 3 saccharin daily presentations. Intra-insular bupivacaine had no effects on familiarity acquisition, but did impair CTA learning in a different group of rats micro-infused before saccharin presentation in a CTA training protocol. Our data indicate that the IC is not essentially involved in acquisition or retention of taste familiarity, suggesting regional dissociation of areas involved in CTA and taste familiarity.
authors.affiliation: Laboratorio de Neurobiologia, Centro de Investigaciones Biomédicas, Facultad de Ciencias Biologicas & Facultad de Medicina, Universidad Andres Bello, Chile.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Moraga-Amaro
authors.affiliation: Laboratorio de Neurobiologia, Centro de Investigaciones Biomédicas, Facultad de Ciencias Biologicas & Facultad de Medicina, Universidad Andres Bello, Chile.
authors.forename: Andrés
authors.initials: A
authors.lastname: Cortés-Rojas
authors.affiliation: Laboratorio de Fisiopatologia Integrativa, Departaemento de Ciencias Biologicas, Facultad de Ciencias Biologicas & Facultad de Medicina, Universidad Andres Bello, Santiago, Chile; Millennium Institute on Immunology and Immunotherapy, Santiago, Chile.
authors.forename: Felipe
authors.initials: F
authors.lastname: Simon
authors.affiliation: Laboratorio de Neurobiologia, Centro de Investigaciones Biomédicas, Facultad de Ciencias Biologicas & Facultad de Medicina, Universidad Andres Bello, Chile. Electronic address: jstehberg@unab.cl.
authors.forename: Jimmy
authors.initials: J
authors.lastname: Stehberg
mesh_terms: D000818:Animals; D001362:Avoidance Learning / Q000502:physiology*; D002540:Cerebral Cortex / Q000502:physiology*; D007266:Inhibition, Psychological; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D021641:Recognition, Psychology / Q000502:physiology*; D055697:Taste Perception / Q000502:physiology*
keywords: Attenuation of neophobia; IC lesion; Ibotenic acid; Insular cortex; Memory retention; Neophobia; Taste familiarity