Meeting Abstract
Efficiently searching natural environments for food, mates, and nesting sites is critical to the survival of all moving organisms. Since most habitats are a mixture of patches that have variable amounts of food, animals must decide when to leave a patch in search of a new one. This decision making process requires that animals either utilize spatial and temporal memory or use a simple rule of thumb. How this type of information is encoded in the brain, and how these decisions are made, is a major open question in neuroethology. The fruit fly, Drosophila melanogaster, is uniquely suited for answering these questions because (a) they exhibit the capacity for temporal/spatial memory; (b) genetic tools make it possible to remotely activate and inactivate small subsets of neurons; and (c) it is possible to observe their behavior in relatively large but controlled environments. To examine the role of temporal/spatial memory in flies’ search behavior, we placed three odor emitting, but food-barren, patches in a 60x60x120 cm^2 wind tunnel. We selected ethanol for the odor because it is highly attractive to flies in search of fermenting fruit. We released six flies into the wind tunnel at a time, and used a machine vision system to track their activity on each of the three patches over the course of 14 hours. Each fly was labeled with a different color of nail polish so that we could keep track of their identities over time, and across patches. Our results indicate that flies spend more time searching for food on their first odor patch. Furthermore, we found that flies spend more time searching on patch if more time has elapsed since their last visit to a patch (p=0.01). Together, these behavioral trends show that flies use temporal memory to make decisions. More research is needed to determine the details of their foraging algorithm, and the exact role that their neurons play in their memory.
