Salk scientists use sound waves to control brain cells

The technology was revealed within a study appearing September 15 in the journal Nature Communications. All they need to do to trigger activity is add a membrane ion channel to a neuron cell and blast it with ultrasonic waves – in this experiment, the researchers changed the worm’s direction through sound bursts. But using an optogenetics approach on cells deep in the brain is hard : typically, researchers have to perform surgery to implant a fiber optic cable that can reach the cells. However, the procedure gets tricky when it comes to cells deep inside the body. The study is basically a sound based approach to activating cells. “In contrast to light, low-frequency ultrasound can travel through the body without any scattering”, he says.

But whereas previous work stimulated particular regions of the brain, sonogenetics shows that it is possible to target a specific cell type or an individual neuron, says Chalasani. First, microbubbles of gas outside of the worm were necessary to amplify the low-intensity ultrasound waves.

“It’s the first demonstration of this genetic enhancement of ultrasound neurostimulation”, said Stephen Baccus, a neurobiologist at the Stanford University School of Medicine, who was not involved in the study. The worms ordinarily use these neuron-embedded TRP-4 channels to sense when their bodies are stretching.

Of course, it’s not like you can ultrasound people’s brains and mind control them because not all membrane ion channels respond to the sound waves.

The team hoped to engineer small groups of worm neurons to express TRP-4 channels and then to open the channels through the mechanical force of ultrasound waves, while allowing non-engineered neurons to remain unperturbed.

With sonogenetics, the team was able to create the same activation effect using ultrasound.

So far, sonogenetics has only been applied to C. elegans neurons.

In optogenetics, scientists add light-sensitive channel proteins to neurons then shine a light on these to selectively open channels. In recent years, says Tyler, researchers have taken a growing interest in the use of ultrasound as a non-invasive way to stimulate brains and nerves, in both animals and humans. And many cells in the human body, he points out, can respond to the influxes of calcium caused by TRP-4.

“The real prize will be to see whether this could work in a mammalian brain”, said Chalasani to the BBC. His group has already begun testing the approach in mice. “[But] when we make the leap into therapies for humans, I think we have a better shot with noninvasive sonogenetics”. Human trails are being planned for the new method. And they also may be useful in therapeutics through the activation of cells affected by disease.

The method is less invasive than light-controlled methods because sound waves do not scatter like light waves do. He then did his post-doctoral research in the laboratory of Dr Cori Bargmann at the Rockefeller University in New York.