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Laser Probes for Brain Experiments

Laser-activated probes stimulate brain cells better, say scientists

3 min read

19 May 2009—Understanding how the brain works typically involves sticking sharp metal electrodes into an animal’s brain and zapping its neurons with electricity. But researchers at Case Western Reserve University, in Cleveland, are working on what could be a more benign, efficient, and effective way to study brain circuits: using light.

The researchers have created a new kind of brain probe by coating the inside of a tiny hollow glass needle with nanoparticles of lead selenide, a semiconductor commonly used in infrared detectors. They insert the needle tips into slices of rat brains and shine infrared light from an 830-nanometer-wavelength titanium-sapphire laser on the probes. The nanoparticles absorb photons and generate an electric field that stimulates neurons, whose signals are recorded using another electrode placed next to them.

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Restoring Hearing With Beams of Light

Gene therapy and optoelectronics could radically upgrade hearing for millions of people

13 min read
A computer graphic shows a gray structure that’s curled like a snail’s shell. A big purple line runs through it. Many clusters of smaller red lines are scattered throughout the curled structure.

Human hearing depends on the cochlea, a snail-shaped structure in the inner ear. A new kind of cochlear implant for people with disabling hearing loss would use beams of light to stimulate the cochlear nerve.

Lakshay Khurana and Daniel Keppeler

There’s a popular misconception that cochlear implants restore natural hearing. In fact, these marvels of engineering give people a new kind of “electric hearing” that they must learn how to use.

Natural hearing results from vibrations hitting tiny structures called hair cells within the cochlea in the inner ear. A cochlear implant bypasses the damaged or dysfunctional parts of the ear and uses electrodes to directly stimulate the cochlear nerve, which sends signals to the brain. When my hearing-impaired patients have their cochlear implants turned on for the first time, they often report that voices sound flat and robotic and that background noises blur together and drown out voices. Although users can have many sessions with technicians to “tune” and adjust their implants’ settings to make sounds more pleasant and helpful, there’s a limit to what can be achieved with today’s technology.

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