Drosophila learn efficient paths to a food source

Abstract

Elucidating the genetic, and neuronal bases for learned behavior is a central problem in neuroscience. A leading system for neurogenetic discovery is the vinegar fly Drosophila melanogaster; fly memory research has identified genes and circuits that mediate aversive and appetitive learning. However, methods to study adaptive food-seeking behavior in this animal have lagged decades behind rodent feeding analysis, largely due to the challenges presented by their small scale. There is currently no method to dynamically control flies' access to food. In rodents, protocols that use dynamic food delivery are a central element of experimental paradigms that date back to the influential work of Skinner. This method is still commonly used in the analysis of learning, memory, addiction, feeding, and many other subjects in experimental psychology. The difficulty of microscale food delivery means this is not a technique used in fly behavior. In the present manuscript we describe a microfluidic chip integrated with machine vision and automation to dynamically control defined liquid food presentations and sensory stimuli. Strikingly, repeated presentations of food at a fixed location produced improvements in path efficiency during food approach. This shows that improved path choice is a learned behavior. Active control of food availability using this microfluidic system is a valuable addition to the methods currently available for the analysis of learned feeding behavior in flies.

Neuromodulatory circuit effects onDrosophilafeeding behaviour and metabolism

“…To further assess the role of neuromodulators in feeding behaviour we assessed the effects of neural silencing on a food-discovery task (Navawongse et al 2016) we refer to as the Small-animal Nutritional Access Chip (SNAC). Liquid food was provided to hungry flies over six sessions and the ability to approach the transient food source was measured.…”

“…A microfluidic feeding assay was performed as previously described (Navawongse et al 2016). Briefly, each microfluidic SNAC chip contained a 20 × 22 mm arena with a feeding alcove connected to a microfluidic channel that is designed to deliver 70 nl of liquid food via an actuator pump.…”

“…The flies were given 10 min to habituate to the chip/incubator environment prior to the start of the experiment. A combined stimulus of blue light with an 85 dB, 300 Hz sound was administered at the onset of the 70 nl liquid food reward (Navawongse et al 2016). The liquid food (5% sucrose 10% red food dye in deionized water) was retracted automatically when the fly was detected inside the feeding alcove or a timeout of 100 sec was reached.…”

“…Six foraging-feeding epochs were imposed in succession with a 120 sec inter-epoch interval. The following parameters were recorded with custom LabView code as previously described: the number of entries into the feeding alcove, time to feed, path efficiency, and the distance travelled during the time the food was presented (Navawongse et al 2016). Task performance was calculated by dividing the number of epochs with successful alcove entries by the total number of epochs.…”

A heuristic underlies the search for relief in fruit flies

“…Invertebrates, particularly insects, are excellent models to study how a less complex brain produces behaviours [19,20]. Insects can be trained to pinpoint a location in space where an unpleasant stimulation ceases, where food may be present, or where a pleasant sensation may be experienced [2,21–23]. Insects explore their environment while relying on multiple sources of information, of which the most studied are visual cues and path integration.…”