Mice tap into their own neural reward circuits with the help of a new optogenetics device.
A microscopic light-emitting diode device that controls the activity of neurons has given researchers wireless control over animal behavior. The tiny device, tested in mice, causes less damage than other methods used to deliver light into the brain, report researchers in Thursday’s issue ofScience, and it does not tether mice to a light source, enabling scientists to study behaviors more naturally than is normally possible.
Many groups of neuroscientists have turned to light-based control of neurons to study the neuronal basis of behavior. To control the brain cells, researchers use optogenetics, a method for genetically modifying neurons that allows them to be activated or silenced with flashes of light.
When Michael Bruchas, a neuroscientist at Washington University in St. Louis, began using optogenetics to study stress-related behaviors in mice, he was frustrated by the limits that tethered devices put on studies involving complex environments or multiple mice. So he teamed up with John Rogers, a materials scientist at the University of Illinois at Urbana-Champaign, and others, to develop a “device that has a very small ultrathin profile, is noninvasive, and can be controlled wirelessly,” says Bruchas. “It gives you more power to study different circuits wired for specific behaviors. Animals can be in their home cage or interacting with another animal or running on a wheel.”
The flexible device is roughly one-fifth the width of a human hair and can be implanted deep inside the brain with the help of a microneedle. A biodegradable adhesive holds the micro-LED implant onto the needle, but that grip is lost as the silk-based adhesive dissolves within a matter of minutes. The device is then left in the brain when the needle is removed. A wire even thinner than the device connects the micro-LED to electronics, including a wireless transmitter, that sit on top of the mouse’s head. Altogether, the setup weighs less than one gram, says Bruchas (a mouse weighs about 30 grams).
This kind of device could eventually be used to control brain activity in an automated fashion: communicating with neurons though flashes of light in response to chemical, temperature, or electrical changes in the brain. “The ability to integrate sensors as well as LEDs could enable ‘closed-loop’ control of brain functions, which could be of use for applications in which information must be both observed and read,” says MIT’s Ed Boyden, one of the co-inventors of optogenetics.
Via Dr. Stefan Gruenwald