Laboratories affiliated with the Cochlear Implant Center are actively involved in both basic and clinical research programs that aim to maximize the benefits available from cochlear implants.
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Research in animal models of deafness at birth provide insights into a broad spectrum of circumstances that affect brain structure and function, particularly as related to a child's ability to learn through developmental stages.We have examined the role that deafness plays in changing the connections within the hearing pathway. We have examined the notion of a "critical period" during which the brain can use restored hearing to open a window of opportunity for refined use of spoken language. Our results suggest that neural connections appear structurally normal very early in life, then begin deafness-induced changes in the pattern of contact between auditory cells in the brain. Research utilizing cochlear implants in animal models has demonstrated the ability to reverse deafness-induced changes in nerves that are critical to introducing activity into the hearing pathway.
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The Cochlear Implant Center tracks educational progress of children with a cochlear implant by using an educational resource matrix (ERM). The matrix was developed on the basis of observations that movement into a mainstream classroom setting is often accompanied by an initial increase in the need for support services, such as interpreters and speech-language therapists. Follow up of school-aged children with implants indicates that these children participate in mainstream education at a substantially higher rate and require diminishing levels of support services than children with similar hearing who use hearing aids. Long-term tracking of educational outcomes of implanted children continues as part of an ongoing assessment of cochlear implant rehabilitation.
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Evaluation of the effectiveness of the cochlear implant in children has largely focused on the perception of speech and on language performance in standardized tests. Because the ultimate goal of cochlear implantation is to facilitate the use of spoken language, there is a clear need to evaluate the strategies adopted by implanted children in spontaneous communication. This information can also guide therapy to promote language learning.
To expand on our assessment of the implant experience in young children, The Cochlear Implant Center has developed a method of video analysis that assesses emerging language even in very young children for whom standardized tests are not useful. Results reveal significant gains in language acquisition in implanted children, who have nearly triple the rate of expressive vocabulary growth compared to children using hearing aids.
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The combination of earlier identification of hearing loss and access to early cochlear implantation has sparked an interest in results in terms of education, economics, emotional development, and cultural effects. The Cochlear Implant Center is studying the emergence of one important aspect of educational success - reading. Our studies are investigating the methods by which newly restored access to all of the frequencies of speech sounds contained in words can be used to generate opportunities to acquire the skills needed to become effective readers.
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The Cochlear Implant Center leads a large multicenter study of the impact of early cochlear implantation on childhood development. The Childhood Development after Cochlear Implantation (CDaCI) study is funded by the NIH. The goal of this longitudinal study is to determine the predictive value of variables as they relate to communication, behavior and educational outcomes of cochlear implantation in young children. The CDaCI study addresses the complexity of language development under conditions of restored hearing in the very young child when a variety of operational skills develop rapidly. The CDaCI study is also helping to determine the impact of medical and hearing assessment tools and parent-child interactions on levels of spoken language, speech recognition, selective attention, psychosocial developmental milestones, and quality of life attained with early cochlear implantation.
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In addition to speech, the cochlear implant is capable of transmitting other complex sounds. The Cochlear Implant Center has been involved in collaborative research with the National Institutes of Health (NIH) in investigating how the cochlear implant conveys the complex information contained by music. By studying patterns of brain activity, it may be possible to design improved methods of encoding sound and training strategies to provide a fuller appreciation of the complex sounds contained in speech and music.
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Like hearing, the sense of balance is based in the ear. Children and adults with severe hearing loss occasionally experience dizziness, vertigo or imbalance before or after cochlear implantation. Extended periods of vertigo and imbalance are rare but, when present, are treatable with exercise programs designed to elicit the brain's natural corrective mechanisms. Research by The Cochlear Implant Center has led to the development of diagnostic tests and treatment approaches that can limit the risk of balance disorders and help guide the choice or ear for cochlear implantation.
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Johns Hopkins outcomes studies have assessed the impact on overall health and quality of life to determine the real-life benefit provided by cochlear implants. Implant users surveyed before and after their operation report dramatic results. These appraisals indicate that the cochlear implant ranks extremely high in the positive impact it has on quality of life and cost-effectiveness. A prospective study of vestibular implantation using the model established by the Cochlear Implant Center cochlear implant studies revealed that vestibular implantation is also likely to be highly cost-effective.
Clinical Trials Currently Recruiting Subjects
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- Who should apply: Otherwise healthy adults with severe vestibular (inner ear balance) sensation loss in both ears and good hearing in at least one ear.
- What's involved: Implantation of a vestibular implant (similar to a cochlear implant, but designed to sense head motion and to restore the inner ear’s sense of head motion and balance)
- Where to learn more: Click here for more information.
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- Who should apply: Otherwise healthy adults with vertigo due to Meniere’s disease in one ear.
- What's involved: Injection of a steroid gel in the middle ear.
- Where to learn more: Click here for more information.
Laboratories Affiliated with The Cochlear Implant Center
The following research labs are currently conducting research related to inner ear disorders that affect The Cochlear Implant Center patients.
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Auditory Brainstem Laboratory
The overall goal of the Auditory Brainstem Library is to understand how abnormal auditory input from the ear affects the brainstem, and how the brain in turn affects activity in the ear through efferent feedback loops. Our emphasis is on understanding the effects of different forms of acquired hearing loss (genetic, conductive, noise-induced, age-related, traumatic brain injury-related) and environmental noise. We are particularly interested in plastic changes in the brain that compensate for some aspects of altered auditory input, and how those changes relate to central auditory processing deficits, tinnitus, and hyperacusis. Understanding these changes will help refine therapeutic strategies and identify new targets for treatment. We collaborate with other labs in the Depts. of Otolaryngology, Neuroscience, Neuropathology, the Wilmer Eye Institute, and the Applied Physics Laboratory at Johns Hopkins, in addition to labs outside the university to increase the impact and clinical relev...ance of our research. view more
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Bowditch Research Group
Bowditch Research Group conducts research regarding speech discrimination in background noise, cochlear implants and osseointegrated hearing devices
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Carey Research Group
John Carey’s Research Group conducts research regarding diseases of the inner ear that affect both balance and hearing mechanisms. Key interests include superior semicircular canal dehiscence syndrome (SCDS), the normal vestibular reflexes and how they change with age, novel intratympanic treatments (i.e., middle ear injections) for conditions like Menière’s disease and sudden hearing loss, and the mechanisms of vestibular migraine. With Lloyd Minor, Dr. Carey helped develop the operation to repair the superior canal in patients with SCDS using image-guided surgery. Dr. Carey has been funded by the National Institutes of Health – National Institute on Deafness and Other Communication Disorders to study inner ear balance function in Menière’s disease and steroid treatment of sudden hearing loss.
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Cochlear Center for Hearing and Public Health
The Cochlear Center for Hearing and Public Health is dedicated to training clinicians, researchers and public health experts to study and address the impact that hearing loss has on older adults and public health. We aim to make measured local, national and global impacts through a macro level (e.g., public policy legislation), micro level (e.g., programs to deliver hearing care to individuals in a particular community), and everywhere in between (e.g., influential research publications, etc.) to adhere to our center’s overall mission and vision of effectively optimizing the health and function of an aging society and become the premier global resource for ground-breaking research and training on hearing loss and public health.
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Fuchs Laboratory
The Fuchs Laboratory uses cellular electrophysiology, immunolabeling and electron microscopy to study synaptic connections between sensory hair cells and neurons in the cochlea. One effort focuses on an unusual cholinergic receptor that mediates efferent inhibition of hair cells, driving discovery of the molecular mechanisms, and offering a target for protection against acoustic trauma. A second topic concerns the small number of unmyelinated "type II" afferent neurons whose synaptic connectivity and response properties argue for a role as the pathway for noxious (too loud) sound. Our studies are motivated by curiosity about fundamental mechanisms, and to provide a foundation for understanding cochlear pathogenesis.
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Glowatzki Lab
Research in the Glowatzki Lab focuses on the auditory system, with a particular focus on synaptic transmission in the inner ear.
Our lab is using dendritic patch clamp recordings to examine mechanisms of synaptic transmission at this first, critical synapse in the auditory pathway. With this technique, we can diagnose the molecular mechanisms of transmitter release at uniquely high resolution (this is the sole input to each afferent neuron), and relate them directly to the rich knowledge base of auditory signaling by single afferent neurons.
We study pre- and post-synaptic mechanisms that determine auditory nerve fiber properties. This approach will help to study general principles of synaptic transmission and specifically to identify the molecular substrates for inherited auditory neuropathies and other cochlear dysfunctions.
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Vestibular NeuroEngineering Lab
Research in the Vestibular NeuroEngineering Lab (VNEL) focuses on restoring inner ear function through “bionic” electrical stimulation, inner ear gene therapy, and enhancing the central nervous system’s ability to learn ways to use sensory input from a damaged inner ear. VNEL research involves basic and applied neurophysiology, biomedical engineering, clinical investigation and population-based epidemiologic studies. We employ techniques including single-unit electrophysiologic recording; histologic examination; 3-D video-oculography and magnetic scleral search coil measurements of eye movements; microCT; micro MRI; and finite element analysis. Our research subjects include computer models, circuits, animals and humans. For more information about VNEL, click here.
VNEL is currently recruiting subjects for two first-in-human clinical trials:
1) The MVI Multichannel Vestibular Implant Trial involves implantation of a “bionic” inner ear stimulator intended to partially restore sensation... of head movement. Without that sensation, the brain’s image- and posture-stabilizing reflexes fail, so affected individuals suffer difficulty with blurry vision, unsteady walking, chronic dizziness, mental fogginess and a high risk of falling. Based on designs developed and tested successfully in animals over the past the past 15 years at VNEL, the system used in this trial is very similar to a cochlear implant (in fact, future versions could include cochlear electrodes for use in patients who also have hearing loss). Instead of a microphone and cochlear electrodes, it uses gyroscopes to sense head movement, and its electrodes are implanted in the vestibular labyrinth. For more information on the MVI trial, click here.
2) The CGF166 Inner Ear Gene Therapy Trial involves inner ear injection of a genetically engineered DNA sequence intended to restore hearing and balance sensation by creating new sensory cells (called “hair cells”). Performed at VNEL with the support of Novartis and through a collaboration with the University of Kansas and Columbia University, this is the world’s first trial of inner ear gene therapy in human subjects. Individuals with severe or profound hearing loss in both ears are invited to participate. For more information on the CGF166 trial, click here. view moreLab Website
Principal Investigator
Charles Della Santina, M.D., Ph.D.
Department
Biomedical Engineering
Otolaryngology - Head and Neck Surgery
