Hideko Heidi Nakajima, M.D., Ph.D.
Assistant Professor, Department of Otology & Laryngology, Harvard Medical School
Eaton-Peabody Laboratories, Mass. Eye & Ear Infirmary
Faculty, Speech and Hearing Bioscience and Technology Program, Division of Health Science Technology, Harvard-MIT
The human auditory system is able to sense sound pressure from the threshold of air vibration smaller than an atomic diameter, over a dynamic range exceeding a million to one, across a frequency range that is far larger than any other sensory system. Our research both addresses fundamental scientific questions about this extraordinary system and develops new and improved methods to diagnose and treat human hearing disease. We accomplish this through experiments on human cadaveric preparations, clinical measurements on live humans, and modeling of the hearing system.
For example, fresh cadaveric preparations are utilized to study the mechanisms and treatment of hearing disease. By making simultaneous pressure measurements on each side of the cochlear partition in fresh human cadaveric temporal bones, we are able to estimate what a live human would hear. This new and powerful technique enables us to investigate human hearing under controlled circumstances, and to answer questions which could not be previously addressed. We study the effects of various diseases such as ossicular lesions and cochlear third-window lesions. This technique allows us to evaluate surgical techniques for a variety of ear diseases. We are also able to study the efficacy of prosthetic devices, such as passive and active middle-ear prostheses, and the use of alternative cochlear stimulus techniques, such as round-window stimulation and bone conduction. Using this approach we can optimize performance and application of these devices and techniques, and develop new prosthetic devices and surgical techniques, without endangering live humans.
Mathematical modeling and non-invasive measurements on live humans are additional key techniques we employ. For example, another topic in our lab is the study and development of non-invasive measurements for differentiating and diagnosing hearing diseases. Laser vibrometry measurements of umbo velocity and acoustic reflectance measurements are promising tools for diagnosing hearing disease. By making clinical measurements on live patients, and correlating these measurements with post-operative results and with related measurements on cadaveric preparations, we are able to develop improved diagnostic methods for hearing disease. These techniques are used in turn to help diagnose disease in the clinic. Likewise, we employ analytical and computational modeling of the acoustic, mechanical and electrical aspects of the auditory system in conjunction with the above techniques to further refine our understanding of the hearing process and disease mechanisms. Through these approaches, we are able to both develop a better scientific understanding of hearing and to directly benefit patients.