Brain Activity Measured While Flies Fly
By Jeanna Bryner, LiveScience Managing Editor
posted: 17 February 2010 08:15 am ET
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Researchers insert a dye-filled glass electrode (pink) into a fruit fly's brain as the fly is flapping its wings. The electrode and the brain are immersed in saline (colored blue). Credit: Gaby Maimon and Michael Dickinson/Caltech
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In a freaky fruit fly experiment, scientists have used electrodes to measure the brain activity of the tiny insects while flapping their wings for the first time. When the animals began to fly, neurons in the visual region of the brain ramped up activity abruptly, they found.

Though fruit fly brains are tiny, packing just 300,000 brain cells, the findings have implications for understanding brain changes in larger animals. For comparison, an average human brain has about 100 billion neurons.

"Our work on Drosophila [fruit flies] is of general interest because sensory neurons in many species — including birds, rodents, and primates — change their response strength depending on the behavioral state of the animal, but why these changes in sensitivity take place is not entirely clear," said study researcher Gaby Maimon of Caltech.

The research was published Feb. 14 in the advance online edition of the journal Nature Neuroscience.

Past recordings of neural-cell activity in fruit flies involved animals that had been stuck or glued down. Working with such a small brain can be a challenge in itself, but Maimon and colleagues wanted to keep the fly alive and active.

"The challenge was to be able to gain access to the brain in a way that didn't compromise the animal's ability to fly, or to perform behavior," said study researcher Michael Dickinson of Caltech. "We couldn't just rip the brain out of the body and put it into a dish."

So the team tethered the fruit fly so that its head was clamped into place while its wings were free to flap. Then, the scientists sliced off a patch of the hard cuticle covering the insect's brain and placed the electrodes onto neurons in the visual region of the brain.

Beneath the hood, a fruit fly's brain looks kind of like a white blob, Dickinson told LiveScience.