Sharon G. Kujawa, Ph.D.
Associate Professor, Otology & Laryngology, Harvard Medical School
Director, Department of Audiology, Mass. Eye and Ear
Noise-induced and age-related hearing losses (NIHL, AHL) are widespread health problems that will continue to increase as our society ages. They are the most common forms of acquired sensorineural hearing loss that we see in our adult patients, often co-existing in the same ears, and they are a primary focus of our research activities. We study how susceptibility to these forms of hearing loss is shaped by genetic background, how noise exposure and age interact to influence auditory functional and neurodegenerative outcomes, and how noise exposed/aging ears can be manipulated pharmacologically to reveal underlying mechanisms or for treatment or prevention. Our collaborators in these studies are geneticists, pharmacologists, physiologists, public health researchers, clinicians, and engineers. Our efforts are directed toward understanding fundamental principles underlying these common forms of hearing loss and facilitating the transfer of this information to better-informed clinical care. One area of current focus in the lab is the aging of noise-exposed ears:
Age-Noise Interactions. Understanding the long-term consequences of noise exposure is critical to public health. The prevailing view is that a noise-induced insult has no ongoing, progressive influences on auditory function: after an acute period of recovery, sensitivity and underlying injury stabilize and subsequent alterations in function are presumed related to other causes, for example aging. Moreover, ears without permanent threshold shifts (PTSs) after noise are thought to be fully recovered from the insult. Our work suggests that these views require substantial revision. We have demonstrated that noise exposure can result in delayed, but dramatic loss of cochlear afferent neurons - even after an exposure in which the noise-induced threshold shift is completely reversible. Since these afferent neurons to inner hair cells (IHCs) constitute 95% of the cochlear nerve, their dysfunction/loss must have important consequences for hearing, even if threshold sensitivity recovers.
Selected Recent References:
Kujawa, SG and Liberman, MC. Adding insult to injury: cochlear nerve degeneration after "temporary" noise-induced hearing loss. Journal of Neuroscience 2009 Nov 11:29(45):14077-85.
Kujawa, SG and Liberman, MC. Acceleration of age-related hearing loss by early noise exposure: evidence of a misspent youth. Journal of Neuroscience 2006 Feb 15:26(7):2115-2123.
Chen, Z, Mikulec, A, McKenna, MJ, Sewell, WF and Kujawa, SG. A method for intracochlear drug delivery in mouse. Journal of Neuroscience Methods 2006 Jan 15;150(1):67-73.
Seixas, NS, Goldman, B, Sheppard, L, Neitzel, R, Norton, S and Kujawa, SG. Prospective Noise Induced Changes to Hearing Among Construction Industry Apprentices. Occupational and Environmental Medicine 2005; 62, 309-317.
Parkinson, NJ, Olsson, CL, Hallows, JL, McKee-Johnson, J, Keogh, BP, Noben-Trauth, K, Kujawa, SG and Tempel, BL. Mutant β-spectrin 4 causes auditory and motor neuropathies in quivering mice. Nature-Genetics 2001; 29, 61-65.