The black box that is the brain just became a little more transparent. This week, neuroscientists and biomedical engineers told the world that they can control a worm’s brain using nothing but ultrasound waves.
The technique,called sonogenetics , builds on another revolutionary method known as optogenetics, which itself is only ten years old. Optogenetics lets neuroscientists turn specially modified neurons on and off using nothing but light, allowing them to conduct controlled experiments unprecedented precision. But the neurons that can be controlled are limited by how far light can penetrate the tissues.
Sonogenetics isn’t as encumbered. Ultrasound waves can easily travel through tissues—they are, after all, what doctors use to see pre-term babies in utero.
Scientists discovered that when Caenorhabditis elegans nematodes were bombarded with ultrasound waves, a protein known as TRP-4 opened a channel in certain neurons’ cell membranes. (Neurons send signals to each other via chemicals that are received through a variety of channels.) The function of TRP-4 was just discovered five years ago , and only some neurons naturally have it. But the researchers found that they could engineer worms to have additional TRP-4-endowed neurons.
Once the worms were ready, researchers needed a few more tweaks to get the system operational. Here’s Jonathan Webb, reporting for BBC News:
To get any responses at all, however, the researchers had to give the worms a bubble bath. Tiny “microbubbles” of gas boosted the power of the low-frequency sound waves.
“The microbubbles grow and shrink in tune with the ultrasound pressure waves,” [lead author] Dr Ibsen explained. “These oscillations can then propagate noninvasively into the worm.”
Bubbles like these are already used to improve the contrast in some medical ultrasound imaging. They can be injected into the bloodstream, which is one reason the team believes their method could eventually work in humans.
Even if the technique doesn’t eventually work in humans, it has the potential to give neuroscientists a deeper perspective on how brains—even basic ones—work. As with other basic research, understanding how even a handful of cells work can lead to unexpected, but welcome, breakthroughs.