Scope-Headed Rats Roam Free

By building a tiny laser microscope small enough to mount on a rat’s head, researchers found a way to solve the puzzle of recording meaningful signals from brain cells that calculate perception and attention while the subject is in motion.

As we interact with the world around us, it is essential that all five of our senses work together simultaneously and seamlessly to allow us to freely explore and make sense of our environment. Like a supercharged GPS, our brain is constantly updating our position in space based on the information received from our senses as well as our motor and vestibular systems, all in real time. The problem for researchers trying to understand how this occurs has always been how to record meaningful signals from the brain cells that do these calculations while we are moving.

To address this problem, researchers at the Max Planck Institute (MPI) for Biological Cybernetics in Tübingen developed a way of actually watching the activity of many brain cells simultaneously in an animal that is free to move around the environment.

By developing a small, lightweight laser-scanning microscope, researchers were able, for the first time, to image activity from fluorescent neurons in animals that were awake and moving around, while tracking the exact position of the animal in space. The microscope uses a high-powered pulsing laser and fiber optics to scan cells below the surface of the brain, eliminating the need to insert electrodes, which are traditionally used, and making the microscope noninvasive to brain tissue.

The fiberscope developed at the Max Planck Institute for Biological Cybernetics attaches to a rat’s head and provides valuable information about how the brain works while a subject is in motion. The microscope uses a high-powered pulsing laser and fiber optics to scan cells below the surface of the brain, eliminating the need to insert electrodes, which are traditionally used, and making the microscope noninvasive to the brain tissue. (Photo: Jason Kerr/©MPI for Biological Cybernetics)

The traditional approach to solving these sorts of questions is to restrain the animal and present it with a series of scenes or movies or images. The miniaturized microscope allows the researchers to turn this paradigm around and allow the animal to freely move around in its environment, while still allowing the scientists to monitor the activity of the brain cells responsible for processing visual information.

It is clear that the brain does not work one cell at a time to recognize the environment, so the microscope records from many cells at a time, allowing the researcher for the first time the ability to look at how the brain is able to generate an internal representation of the outside world while using natural vision.

“We need to let the animal behave as naturally as possible if we want to understand how its brain operates during interaction with complex environments. The new technology is a major milestone on the way to helping us understand how perception and attention work,” said Jason Kerr, lead author of a study on the work appearing this week in the online early edition of Proceedings of the National Academy of Sciences.

For more information, visit: www.kyb.mpg.de