Measurement of Taste Memory in Drosophila

Abstract

The ability to modify behavior as a result of previous experience allows an organism to adapt to changes in its environment. Even innate behaviors, like feeding initiation, can change if previously associated with a noxious stimulus. Here, we describe a taste memory assay pairing appetitive and bitter tastants, resulting in aversive taste conditioning. By training a fly to associate sweet sucrose applied to the tarsus with bitter quinine applied to the proboscis, flies quickly learn to suppress the reflexive proboscis extension to sucrose, providing a bioassay for behavioral and molecular plasticity. This single-fly taste memory assay may be applied to adult Drosophila of any genetic background and allows for interrogation of the neural circuitry and molecular processes encoding memories while simultaneously measuring behavior. Unlike many other memory assays, this system requires few custom components, and therefore can be easily established in laboratories with minimal expertise in the study of fly behavior.

FIGURE 1.

Schematic of the aversive taste memory assay. First, initial responses to sugar were assessed (pretest). Next, flies were trained by pairing sugar with quinine presentation, immediately following tastant application (training). The proboscis-extension response (PER) in response to sucrose was then tested in the absence of quinine (test). In control experiments (naive flies), the same procedure was followed, but quinine was not applied to the proboscis.