Ever wondered what’s going on in a fruit fly’s mind? A team of researchers has built a window to the creature’s brain, potentially probing what goes on during mating, learning and memory and other activities ruled by neural processes.

Called “Flyception,” the new imaging system created by scientists from the University of California San Diego sees brain activity in freely walking fruit flies. For the first time, they saw what happens in the fly’s brain during courtship — a time when it’s unrestrained.

“Brain imaging is essential for advancing our understanding of the neural mechanisms underlying behavior and cognition,” said study author Takeo Katsuki, highlighting their work as a step toward the ambitious goal of neuroscience today to map the organ’s activity at a whole brain scale in animals.

While imaging the brain of the fruit fly has been widely done, most conventional methods immobilize its head under the microscope, which could preclude natural actions such as during courtship. Brain responses during many basic fly behaviors thus remain mysterious.

How did the team undertake this project?

First, they surgically removed a section of the fly’s exoskeleton covering the head, approximating the size of a couple of grains of salt. They then sealed the gap using a transparent silicon adhesive topped with a coverslip or a flat and clear material typically used for viewing microscope slides.

This formed a window exposing the protocerebrum, the upper half of the fly’s brain.

Next, the researchers devised a way to look inside the said window to monitor the fly's brain activity while in a romantic state. Since flies do not really stay still, the team created unique computer vision techniques made up of three cameras and rotating mirrors.

Two separate cameras tracked the window on the fly's skull as it keeps moving, controlling the mirrors’ position so the animal’s head stayed in center view. A laser beam also bounced off the mirrors and the fly head, prompting fluorescent markers to light up certain brain neurons.

A third high-sensitivity camera recorded neural activity — the intricate system delivering real-time feedback at 1,000 frames every second.

While different from mammal brains, fly brains are good to study, as they are quite small with only around 100,000 neurons but complex enough to let researchers investigate social and cognitive behaviors.

The findings were published in the journal Nature Methods.