Shuman He

About

Biography

I am the vice chair of research for the Department of Otolaryngology - Head and Neck Surgery. My current research projects include:

Neural encoding and auditory perception in cochlear implant users

Cochlear implant (CI) users who are 65 years or older typically show poorer speech perception performance than younger adult CI users, especially in competing background noise. The underlying mechanisms remain unclear. Whereas declined cognitive function has been proposed as the major factor, deteriorations in the auditory system have also been suggested to be the primary reason. As a result, there is no robust indicator for optimizing programming settings or habilitation strategies for older implanted patients. The long-term goal of this research is to better understand the neurophysiologic basis of speech perception deficits in older (≥ 65 years) CI users. As the first step to achieve this long-term goal, this study is designed to better understand underlying neurophysiological mechanisms of speech perception deficits in older CI users. Older listeners are known to have temporal processing deficits, and temporal cues are particularly important for discriminating speech in CI users. Therefore, the proposed study will focus on comparing peripheral and central auditory neural encoding of, and perceptual sensitivity to, temporal envelope cues between younger and older adult CI users.

Neural encoding and auditory processing of electrical stimulation in pediatric cochlear implant users

Cochlear nerve deficiency (CND) refers to a small or absent cochlear nerve (CN) as revealed by high-resolution magnetic resonance imaging. Cochlear implantation has been used as a treatment option for children with CND for nearly two decades. Due to the lack of understanding of how electrical stimulation is encoded and processed in their auditory system, there is still no evidenced-based clinical practice for managing this unique patient population. To further complicate matters, more than half of children with CND cannot provide reliable behavioral responses despite their age due to severe comorbidities. As a result, clinicians often use a combined “one-size-fits-all” and “try-and-see” approach to program cochlear implant (CI) speech processors for children with CND. This practice typically results in stimulating all intra-cochlear CI electrodes with similar programming parameters. However, recent work from our lab showed that the likelihood of measuring CN neural responses in children with CND reduced as the stimulating CI electrode site moved from the base to the apex of the cochlea. This unique response-deterioration pattern is not observed in children with normal-sized CNs. In addition, our compiling preliminary data show that information transmitted by CI electrodes with no measurable CN response is only adequate for auditory detection but not sufficient for auditory discrimination, which explains why the majority of children with CND do not make satisfactory progress in speech and language development despite good auditory detection thresholds with their CIs. These new findings suggest that the current clinical practice is unlikely to provide appropriate CI programming settings for this unique patient population. Therefore, there is an urgent need to develop objective clinical tools for optimizing CI settings for individual children with CND. Our long-term goals are 1) to understand neural encoding and processing of electrical stimulation in children with CND, and 2) to develop an effective, evidence-based clinical practice for managing this unique patient population. As the first step toward these long-term goals, this study aims to better understand neural encoding and processing of electrical stimulation in both the CN and the central auditory system in implanted children with CND.

Auditory function in implanted patients with Usher Syndrome

Usher syndrome (USH) is an autosomal recessive disorder characterized by hearing loss, visual impairment, and in some cases, vestibular dysfunction. It is the leading cause of hereditary deaf-blindness in humans. USH causes extensive degeneration in the cochlear nerve (CN), especially in CN fibers innervating the base of the cochlea. Whereas there is no treatment for arresting this degenerative process or for restoring visual loss, the restoration of auditory input is possible with cochlear implantation. Due to the progressive deterioration in vision, using visual cues for communication will eventually become impossible. Therefore, the importance of optimizing auditory inputs through cochlear implants (CIs) for patients with USH is paramount. However, patients with USH have much higher rates of neurological, mental, or behavioral disorders than the general CI patient population, which limits their ability to provide reliable behavioral responses or sufficient verbal descriptions of their auditory perception, especially for pediatric patients. In addition, optimal programming parameters for CI users with CN damage differ from those used in typical CI users due to declined CN responsiveness to electrical stimulation. As a result, the clinical programming process in implanted patients with USH can be extremely challenging. To date, auditory neural encoding of electrical stimulation in patients with USH has not been systematically evaluated. Consequently, the field lacks evidence-based practice guidelines for managing implanted patients with USH. For patients who cannot provide reliable feedback, clinicians rely on a “trial-and-error” approach for adjusting CI programming settings, which ultimately may not result in appropriate programming maps for individual patients. Therefore, there is an urgent need to develop objective clinical tools for optimizing CI settings for these patients. As the first step toward developing evidence-based practice for managing patients with USH, this study evaluates local neural health, as well as the neural encoding of temporal and spectral cues at the CN in implanted patients with USH.

Additional research

In addition to these three main projects described above, we are collaborating with Dr. Raymond L. Goldsworthy at University of Southern California on studies investigating 1) neural encoding and auditory perception of temporal fine structure, and 2) music appreciation in cochlear implant users. We are also collaborating with Dr. Aaron C. Moberly at The Ohio State University College of Medicine on a research study that aims to identify predictive factors for speech perception in adult cochlear implant users.

Credentials

Research