Fruit flies are far from human, but not as far as you might think.
They do many of the same things people do, like seek food, fight and woo mates. And their brains, although tiny and not set up like those of humans or other mammals, do many of the same things that all brains do â€” make and use memories, integrate information from the senses, and allow the creature to navigate both the physical and the social world.
Consequently, scientists who study how all brains work like to use flies because itâ€™s easier for them to do invasive research that isnâ€™t allowed on humans.
The technology of neuroscience is sophisticated enough to genetically engineer fly brains, and to then use fluorescent chemicals to indicate which neurons are active. But there are some remaining problems, like how to watch the brain of a fly that is moving around freely.
It is one thing to record what is going on in a flyâ€™s brain if the insectâ€™s movement is restricted, but quite another to try to catch the light flash of brain cells from a fly that is walking around.
Takeo Katsuki, an assistant project scientist at the Kavli Institute at the University of California, San Diego, is interested in courtship. And, he said, fruit flies simply wonâ€™t engage in courtship when they are tethered.
So he and Dhruv Grover, another assistant project scientist, and Ralph J. Greenspan, in whose lab they both work, set out to develop a method for recording the brain activity of a walking fly.
One challenge was to track the fly as it moved. They solved that problem with three cameras to follow the fly and a laser to activate the fluorescent chemicals in the brain.
The other was the delicate matter of making a window into the flyâ€™s brain. For that, Dr. Katsuki said, he removed the top of a flyâ€™s head and glued in place a tiny glass window. It had to seal off the brain so that it wouldnâ€™t dry out, and it had to be flat, to avoid optical distortion.
The procedure was quite a delicate matter. Now, Dr. Katsuki said, â€œI call myself a fly surgeon.â€
And although the flies often seemed fine after the procedure and walked away, the researchers let them rest for a day, to make sure. If the surgery did not go well, a flyâ€™s brain activity might be abnormal, and if there was a problem, a fly would probably not survive a day.
Dr. Katsuki said that he was sometimes disappointed when surgery went well but the patient escaped by flying away instead of being captured in a vial to await the next dayâ€™s experiment. But he and his colleagues operated on enough flies to prove the value of the procedure.
The researchers published the details of their work in Nature Methods in May. Now that they have shown the approach works, they can start finding out what they want to know about how a flyâ€™s brain works.
Source: The New York Times
Writer: James Gorman