LiCl-induced sickness modulates rat gustatory cortical responses

Abstract

Gustatory cortex (GC), a structure deeply involved in the making of consumption decisions, presumably performs this function by integrating information about taste, experiences, and internal states related to the animal’s health, such as illness. Here, we investigated this assertion, examining whether illness is represented in GC activity, and how this representation impacts taste responses and behavior. We recorded GC single-neuron activity and local field potentials (LFPs) from healthy rats and rats made ill (via LiCl injection). We show (consistent with the extant literature) that the onset of illness-related behaviors arises contemporaneously with alterations in 7 to 12 Hz LFP power at approximately 12 min following injection. This process was accompanied by reductions in single-neuron taste response magnitudes and discriminability, and with enhancements in palatability-relatedness—a result reflecting the collapse of responses toward a simple “good-bad” code visible in the entire sample, but focused on a specific subset of GC neurons. Overall, our data show that a state (illness) that profoundly reduces consumption changes basic properties of the sensory cortical response to tastes, in a manner that can easily explain illness’ impact on consumption.

Learning enhances representations of taste-guided decisions in the mouse gustatory insular cortex

“…Despite the advantages offered by the GC as a model for studying plasticity, 36 , 41 , 42 and its well-demonstrated role in conditioned taste aversion, 36 , 39 familiarity learning, 43 , 44 and associative learning, 35 , 45 , 46 few studies have investigated the GC’s involvement in taste discrimination learning. Work in rodents has shown that lesions of the GC impact salt discrimination learning, confirming a role for this region in this process.…”

Learning enhances representations of taste-guided decisions in the mouse gustatory insular cortex

“…GC encodes sensory, affective and cognitive signals through time varying patterns of activity 11,13,[32][33][34][35][36][37] . Electrophysiological recordings in mice performing a 2-AC show a temporal separation between sensory processing and decision-related activity, with the first occurring mostly during sampling and the second manifesting itself as preparatory activity preceding decisions on directional licking 17 .…”

“…Despite the advantages offered by GC as a model for studying plasticity 33,38,39 and its welldemonstrated role in conditioned taste aversion 33,36 , familiarity learning 40,41 and associative learning 32,42,43 , few studies have investigated GC's involvement in taste discrimination learning. Work in rodents has shown that lesions of GC impact salt discrimination learning, confirming a role for this region in this process 44 .…”