Innate and Conditioned Taste Processing in Drosophila

Peripheral detection of tastants allows animals to detect the dietary value of food and its potential toxicity. Many tastants such as sugars and fats elicit reflexive appetitive responses, whereas other foods such as quinine induce aversion. The relative value of food can change in accordance with an animal's internal state and prior experience. Understanding the neural and genetic bases for the detection and response to tastants, as well as how these behaviors change with experience, is central to sensory neuroscience. The presentation of attractive tastants to the proboscis or legs of the fruit fly Drosophila melanogaster induces a robust and reflexive proboscis-extension response (PER). This quantifiable response can be used to study the receptors underlying taste detection, the neural circuits involved in sensory processing, and the musculature required for a simple feeding behavior. Furthermore, we have developed a memory assay pairing appetitive and bitter tastants, resulting in aversive taste conditioning, in which the PER response to attractive tastants is diminished. Unlike many memory assays, this assay does not require specialized equipment and can be readily implemented in teaching and research laboratories. Here, we introduce protocols for studying the PER feeding response and aversive taste memory in Drosophila.