By Massachusetts Eye and Ear/Harvard Medical School
Many profoundly deaf people wearing cochlear implants (CIs) still face challenges in everyday situations, such as understanding conversations in noise. Even with CIs in both ears, they have difficulty making full use of subtle differences in the sounds reaching the two ears (interaural time difference, [ITD]) to identify where the sound is coming from. This problem is especially acute at the high stimulation rates used in clinical CI processors.
A team of researchers from Massachusetts Eye and Ear/Harvard Medical School, including past funded Emerging Research Grantee, Yoojin Chung, Ph.D., studied how the neurons in the auditory midbrain encode binaural cues delivered by bilateral CIs in an animal model. They found that the majority of neurons in the auditory midbrain were sensitive to ITDs, however, their sensitivity degraded with increasing pulse rate. This degradation paralleled pulse-rate dependence of perceptual limits in human CI users.
This study provides a better understanding of neural mechanisms underlying the limitation of current clinical bilateral CIs and suggests directions for improvement such as delivering ITD information in low-rate pulse trains.
The full paper was published in The Journal of Neuroscience and is available here. This article was republished with permission of the Massachusetts Eye and Ear/Harvard Medical School.
Dr. Yoojin Chung, Ph.D. was a 2012 and 2013 General Grand Chapter Royal Arch Masons International award recipient through our Emerging Research Grants program. Hearing Health Foundation would like to thank the Royal Arch Masons for their generous contributions to Emerging Research Grantees working in the area of central auditory processing disorders (CAPD). We appreciate their ongoing commitment to funding CAPD research.