A brain scan imaged by the new tracking system is seen superimposed on a picture of a fruit fly. Photo by Takeo Katsuki/Kavli Institute for Brain and Mind/UC San Diego
SAN DIEGO, May 17 (UPI) -- Researchers in California have developed a technique for imaging the brain activity of an unrestrained, freely walking fruit fly. Scientists are now using the new method to monitor the fruit fly's brain during courtship.
Fruit flies, Drosophila melanogaster, are almost as ubiquitous as mice in research labs. Their relatively simple brains allow scientists to explore the evolutionary origins of various neurological pathways. Until now, researchers have only been able to image the brain activity of stationary fruit flies.
Current imaging technologies require the fruit fly's head to be positioned beneath a microscope, complicating the ability to study a fly's brain while moving. For this reason, a variety of fly behaviors and their neurological roots -- mating, fighting, sleep, learning and memory -- are poorly understood.
To solve this problem, scientists at the University of California, San Diego first created a window into the upper half of the fruit fly's brain, the protocerebrum. Researchers removed a piece of exoskeleton from the top of the fly's head and sealed it with a transparent silicon adhesive. They overlaid the window with a coverslip to enable imaging.
Next, researchers designed a series of mirrors and cameras to track the fruit fly as it moved freely. The mirrors and cameras allow a laser beam to follow the fly's movements. The laser excites neural markers that a high-sensitivity camera records.
The system is capable of tracking the movement of the fly's neurons in real time, operating at a speed of 1,000 frames per second.
Researchers detailed their new imaging technology this week in the journal Nature Methods.
"Brain imaging is essential for advancing our understanding of the neural mechanisms underlying behavior and cognition," study co-author Takeo Katsuki, a research scientist at UC-San Diego's Kavli Institute for Brain and Mind, said in a news release.
"One of the biggest goals of today's neuroscience research -- as outlined by the national BRAIN Initiative -- is to map brain activity at a whole brain scale in naturally behaving animals, so that we can understand how higher-order cognitive functions,and disorders, emerge through the concerted activity of multiple brain regions," Katsuki added. "The technology we developed provides a first step toward this goal by enabling monitoring brain activity in naturally behaving fruit flies."