Combining complementary skills, a team of neuroscientists studies how flies navigate their surroundings.

Some collaborations click from the start. Take the chance meeting three years ago at Janelia Farm Research Campus between Michael Reiser, a group leader at Janelia, and Charles Zuker, an HHMI investigator then at the University of California, San Diego (UCSD). The two had never spoken before, but within a day or two, Reiser says, Zuker was suggesting his graduate student as a perfect fit for the project.

The partnership seemed so promising that Zuker arranged to work with Reiser through Janelia Farm’s Visitor Program, where scientists from around the world conduct research of their own design for a few weeks or several years (see sidebar, “Visitor’s Welcome”). “We all hit it off beautifully,” he says.

The researchers weren’t just simpatico. They brought together complementary talents and knowledge that enabled them to explore an important question: do fruit flies commit details of their surroundings to memory? Humans and other vertebrates make spatial memories all the time. You can return to your car in a crowded parking lot, for example, by referencing landmarks stored in memory. So-called place neurons in the hippocampus, a brain structure crucial to memory, confer this ability. “In essence, the cells are creating an internal map of the outside world,” says Zuker.

		Fly Place Learning: Thermal Visual Arena When the cool tile (yellow) and the visual panorama are shifted together, flies are able to locate the cool tile more quickly over time. Fly Memory: Coupled Visual Panorama When the cool tile is moved (yellow) but the wall patterns remain the same, the flies head for where the cool tile used to be (red). Fly Memory: Uncoupled Visual Panorama When the flies are trained without visual stimulus and the cool tile is moved, the flies wander around randomly.

But how do neurons register this information? Reiser believes it might be possible to dissect mapping of spatial memory by analyzing the process in fruit flies, where brain cells can be precisely targeted for manipulation. “The fly presents a real sweet spot to try to answer this question,” he says.

At the outset, Reiser brought his LED-based display that projects different background patterns, providing potential navigation landmarks for flies. Zuker brought small, hot and cool tiles that his lab had developed to study how the insects sense temperature.

The job of melding these technologies fell to the third member of the partnership, Tyler Ofstad—Zuker’s graduate student and an M.D./Ph.D. candidate at UCSD. After a year of R&D in Reiser’s lab, handled largely by Ofstad with what Zuker calls “devotion, drive, and maniacal commitment,” the team had built a shallow, circular arena, about 20 centimeters across, with a clear glass lid. Most of the arena’s floor was a warm-to-the-touch 36°C. One tile, however, was only 25°C, pleasantly cool for fruit flies. Each time the flies entered the arena, they typically wandered, but “once they found the cool spot, they stopped and stayed there,” says Ofstad. The flies were allowed 10 five-minute trials to learn the location of the tile. To follow the flies’ movements, the researchers were among the first to use software designed by Janelia Farm fellow Kristin Branson that Reiser describes as “the world’s best fly tracking program.”

Illustration: Mike Lemanski

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