Marmosets Have Excellent Hearing, and That Might Help Improve Tech for the Deaf

Marmosets' ability to distinguish pitches is as good as humans'. Universal Images Group via Getty Images

There's always room for improvement in technology, at least if scientists and their trusty marmoset sidekicks have anything to say about it. Recently, researchers at Johns Hopkins University revealed marmosets are the only nonhuman animals that can hear different pitches of music and language in the same way that people can. Considering this similarity, scientists from the same lab conducted a new study of marmosets to better understand speech and hearing in humans.

In the new study, researchers electrically stimulated the brains of four common marmosets that were deaf in one ear. This stimulation is similar to how cochlear implants work. Hundreds of thousands of deaf and partially deaf people worldwide use cochlear implants to stimulate the auditory nerve. The device doesn't allow for full hearing, but rather helps deaf people interpret sounds and understand speech without lipreading.

But the electrical signals failed to affect the auditory areas of the marmosets' brain in the same manner that regular sound does, and many neurons involved in sound and pitch perception remained inactive during the experiment. The researchers believe this could be because the electrical current turns on neurons that would be left alone during normal processing of sound. Once activated, these neurons disrupt normal hearing ability.

Since cochlear implants fall short of helping people adequately distinguish differences in pitch, this discovery is likely to help researchers tweak hearing devices for better results. Ideally, future models would target sound-related neurons that were previously unaffected by electrical stimulation. Studies of marmosets with new cochlear implant models are underway, a promising sign for the future of hearing loss treatment.