In the study, recordings of acoustic tuning curves were made for 403 neurons in normal-hearing adult gerbils. Recordings during laser stimulation were made for 154 of those neurons; 67 of them responded, and 87 (mostly low-frequency neurons of less than 1 kHz) did not, Dr. Littlefield said. The team made subsequent auditory recordings after the stimulation to make sure that the laser had not done any damage.
Explore This IssueJune 2010
“Of course, there’s many steps between an idea and technological maturity,” Dr. Littlefield said. But he called these early indications “promising.”
Jose Fayad, MD, of the House Ear Clinic in Los Angeles, who has done extensive research on cochlear implants, said the results are exciting. “It’s showing us that we can access the cochlear nerve and we can access the auditory nerve fibers and stimulate them with a completely different stimulus than we have been using up until now,” he said. “When the auditory nerve fails, we go to amplification to loud sound, or we have been going to electricity to do these stimulations. And now we’re talking about light.”
Dr. Fayad said he sees the implications of this research for cochlear implants. “Probably in the future we will be seeing new cochlear implants using light in order to stimulate the cochlear nerve,” he said. “And with light sources we can be shining it through the round window, which means we don’t have to invade the inner ear. And we can manipulate the signal in a way where we can apply this to many kinds of hearing loss.”