Taste is responsible for evaluating the nutritious content of food, guiding essential appetitive behaviours, preventing the ingestion of toxic substances, and helping to ensure the maintenance of a healthy diet. Sweet and bitter are two of the most salient sensory percepts for humans and other animals; sweet taste allows the identification of energy-rich nutrients whereas bitter warns against the intake of potentially noxious chemicals1. In mammals, information from taste receptor cells in the tongue is transmitted through multiple neural stations to the primary gustatory cortex in the brain2. Recent imaging studies have shown that sweet and bitter are represented in the primary gustatory cortex by neurons organized in a spatial map3,4, with each taste quality encoded by distinct cortical fields4. Here we demonstrate that by manipulating the brain fields representing sweet and bitter taste we directly control an animal’s internal representation, sensory perception, and behavioural actions. These results substantiate the segregation of taste qualities in the cortex, expose the innate nature of appetitive and aversive taste responses, and illustrate the ability of gustatory cortex to recapitulate complex behaviours in the absence of sensory input.
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We particularly thank H. Fischman and R. Lessard for suggestions, and members of the Zuker laboratory for comments. We also thank D. Salzman, K. Scott, and R. Axel for discussions. This research was supported in part by a grant from the National Institute of Drug Abuse (DA035025) to C.S.Z., and the Intramural Research Program of the National Institutes of Health, National Institute of Dental and Craniofacial Research (to N.J.P.R.). C.S.Z. is an investigator of the Howard Hughes Medical Institute and a Senior Fellow at Janelia Farms Research Campus, Howard Hughes Medical Institute.
Extended data figures
A mouse expressing ChR2-YFP in the bitter cortex before and after photostimulation. First trial, control experiment with the animal robustly drinking water (yellow circle indicates trial-initiation). Second trial shows prototypical orofacial responses (normally triggered by oral presentation of bitter tastants), now elicited by direct stimulation of bitter cortex (5-10 mW). Third trial shows gaping responses, and attempts to clean the mouth of the "fictive" bitter taste following strong stimulation (10-20 mW); note that the animal does not even sample the water drop; under these stimulating conditions ∼30% of the animals exhibit gagging behaviour. Stimulation of sweet cortex never induced such behaviour.
About this article
Sour Promotes Risk-Taking: An Investigation into the Effect of Taste on Risk-Taking Behaviour in Humans
Scientific Reports (2018)