Laser Probes for Brain Experiments

Activating neurons with light instead of electricity isn’t a new idea, but the Case Western researchers are the first to use real brain tissue instead of neuron cultures, says Spencer Smith, a neuroengineer at the University College London. Other groups have grown neurons on top of thin silicon films connected to electrodes. The setup uses photoconductivity: Shining light on a patch of the film increases its conductivity, increasing current flow and triggering neurons on that patch.

Michael Colicos, a physiology and biophysics professor at the University of Calgary, in Canada, has worked on the photoconductive approach but sees promise in the Case Western technology. ”The advantage of the new technique is that you don’t need the current pulse from the material,” he says. ”The fact that you can liberate yourself from having to be directly electrically coupled with the electrode is a big step forward.”

Colicos finds the trick of coating the inside of the glass tip innovative, since the nanoparticles don’t touch the brain cells directly, reducing toxicity concerns. Strowbridge says his team did not see any evidence of damage to neurons over a few hours of testing with the electrodes nestled right next to the neurons. But they still need to do extensive toxicity studies.

There’s a ways to go before the researchers will be able to implant and control the circuits in a living brain. For now, they plan to make a lead selenide–coated glass surface and test brain slices placed on top. ”From that we can create flexible substrates that we can place right over the surface of the brain,” Strowbridge says. ”We’re certainly not there yet, but that’s where the technology is headed.”