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Authors & Affiliations
Fei-Yang Huang, Fabian Grabenhorst
Abstract
Nutrients and oral-sensory food qualities influence the subjective valuation of food. We recently showed that monkeys prefer sugar- and fat-rich foods, consistent with the integration of nutrient and oral-sensory properties into economic values to guide choice (Huang et al., 2021) and reinforcement learning (Huang & Grabenhorst, 2023). However, it is unclear how amygdala neurons, which encode subjective values during economic choice (Grabenhorst et al., 2012, Jezzini & Padoa-Schioppa, 2020), process nutrients and oral-sensory food attributes during choice. Here, we recorded the activity of 208 amygdala neurons from two rhesus macaques (Macaca mulatta) when they repeatedly chose from eight dairy-based liquid rewards that varied in nutrients (fat, sugar) and oral-sensory properties (viscosity, sliding friction). In each trial, two visual cues, each indicating one of the eight rewards, were sequentially presented to the monkeys, followed by a touch choice to obtain the chosen reward. Mixed-effects logistic regression (n = 18,704 and 22,170 choices from monkey Ya and Ym) revealed subjective but systematic preferences for fat and sugar content in both monkeys. Consistent with our previous results (Huang et al., 2021, PNAS), oral-texture properties (viscosity, sliding friction) mediated the effect of fat on food choice. Apart from encoding the subjective values of offered options (offer value), significant proportions of amygdala neurons also signaled nutrient and oral-sensory reward properties. Our findings suggest that amygdala neurons encode both behaviourally relevant nutrient and oral-sensory food properties and their integrated values, providing essential neuronal substrates for constructing subjective value during economic choice.