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Neuronal Ensembles in the Infralimbic Cortex Dynamically Process Distinct Aspects of Hedonic Value

J Neuro

Authors: Seth W. Hurley, Joaquin E. Douton and Regina M. Carelli
Publication: Journal of Neuroscience
Date: October 10, 2023
Link to article: https://www.jneurosci.org/content/early/2023/10/08/JNEUROSCI.0253-23.2023.long


Hedonic processing is critical for guiding appropriate behavior, and the infralimbic cortex (IL) is a key neural substrate associated with this function in rodents and humans. We used deep brain, in vivo calcium imaging and taste reactivity (TR) in freely behaving male and female Sprague Dawley rats to examine whether the infralimbic cortex is involved in encoding innate versus conditioned hedonic states. In experiment 1, we examined the IL neuronal ensemble responsiveness to intraoral innately rewarding (sucrose) versus aversive (quinine) tastants. Most IL neurons responded to either sucrose only or both sucrose and quinine, with fewer neurons selectively processing quinine. Among neurons that responded to both stimuli, some appear to encode hedonic processing. In experiment 2, we examined how IL neurons process devalued sucrose using conditioned taste aversion (CTA). We found that neurons that responded exclusively to sucrose were disengaged while additional quinine-exclusive neurons were recruited. Moreover, tastant-specific neurons that did not change their neuronal activity after CTA appeared to encode objective hedonic value. However, other neuronal ensembles responded to both tastants and appear to encode distinct aspects of hedonic processing. Specifically, some neurons responded differently to quinine and sucrose and shifted from appetitive-like to aversive-like activity after CTA, thus encoding the subjective hedonic value of the stimulus. Conversely, neurons that responded similarly to both tastants were heightened after CTA. Our findings show dynamic shifts in IL ensembles encoding devalued sucrose and support a role for parallel processing of objective and subjective hedonic value.

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