A study published recently in JAMA Otolaryngology – Head & Neck Surgery found that the ideal placement of electrodes in a cochlear implant differs depending on whether the implant’s purpose is to enhance perception of speech or music.
While speech perception has been the primary focus of cochlear implantation in the past, recent research has studied how patients hoping to gain or regain the ability to hear music can benefit from cochlear implants.
The study built on previous research conducted at Vanderbilt University Medical Center that pioneered the process of image-guided cochlear implantation. A research team led by first author Katelyn Berg, AuD, PhD, sought to understand how the placement of electrodes can affect the perception of different types of auditory input. By taking imaging of the patients’ ears through postoperative CT scans, researchers were able to analyze patients who saw improved music perception based on the location of the electrodes.
Previously, audiologists generally assumed that processes that improved speech perception would also improve music perception. Contrasting with that line of thought, the study found that while implanting electrodes closer to the target nerve cells improves speech perception, patients prioritizing improvements to music perception should receive electrode implants farther away from the target nerve cells.
“We should modify how we counsel patients and consider programming the implant for different inputs based on what the patient wants instead of using a one-size-fits-all approach,” said Berg. “What works for speech may not work for music. The underlying assumption in the field has been that if we get better speech perception, then music will come along too. And that’s not really the case because [with] electrode placement…different factors impacted music versus speech.”
Berg noted that the results of the study showed that some, but not all, patients benefited from image-guided programming in the cochlear implantation process. Next, she said, comes the step of determining why some benefited and others did not.
Underlying the findings of the study is the focus on what Berg calls “the biggest problem in cochlear implant stimulation” — channel interaction.
“Channel interaction is when there is significant overlap in electrical stimulation between neighboring electrodes that smears the sound because you’re in a fluid-filled space,” Berg explained. “We’re always trying to minimize channel interaction to get the clearest signal possible, whether that’s for speech or for music.”
Berg notes that the ideal future of cochlear implant technology would see advances that help patients improve their ability to perceive both speech and music, but that research is still in the early stages. And to progress toward that goal, more research lies ahead.
“I really think there’s a lot of research to be done delving into why there are these differences in electrode placement for music versus speech,” said Berg.
Berg is also interested in finding ways to change music to help users of cochlear implants experience it and determining how changing implant device settings can improve hearing outcomes.
“This paper was focused on music. I am a musician. That’s why I got into this field,” said Berg. “It’s sort of a passion project.”
Other Vanderbilt contributors to the study are Jack Noble, PhD, and Benoit M. Dawant, PhD, as well as senior author René Gifford, PhD, who left VUMC following the conclusion of the study.
The researchers received support from the National Institute on Deafness and Other Communication Disorders (grants F32DC020347, R01DC014462, R01DC009404, R01DC008408, R21DC012620 and R01DC014037), the National Center for Advancing Translational Sciences (grant UL1TR000445) and a Vanderbilt University Discovery grant.
