As you would expect from a program with such diverse expertise, SHBT has produced breakthroughs in fields from bioiphysics to biomedical imaging, from molecular biology to regenerative medicine. Some highlights:
Regenerative Medicine - 2006
Dr. Albert Edge and colleagues have successfully induced human embryonic stem cells to differentiate into progenitor cells that can give rise to several cell types of the inner ear. When grafted into the inner ear, these neural progenitor cells made synaptic connections with nearby hair cells, replacing damaged auditory neurons. The ability to regenerate these neurons can potentially increase the effectiveness of various treatments for hearing loss, including existing ones such as cochlear implants and future ones based on hair cell regeneration.
Neuroscience - 2011
Tinnitus, the ongoing perception of sound in the absence of any physical stimulus, is a common clinical condition lacking effective treatments. Hyperacusis, in which sound intensities considered comfortable by most people are unbearably loud, can accompany tinnitus. Using fMRI and evoked potentials, the Tinnitus Research Unit at MEEI, led by Dr. Jennifer Melcher, has demonstrated that people with tinnitus and hyperacusis show elevated responses to sound within the auditory brain. The elevations may reflect disinhibition at or below the level of the midbrain and/or top-down effects such as over-attention to the auditory domain.
Neural Prostheses - 2010
A team of scientists led by Dr. Daniel Merfeld invented and developed a vestibular implant, the first of its kind, restoring the ability to maintain balance for those who have lost this sense due to inner ear disease. The technology has recently been licensed to a manufacturer to develop this device for clinical use.
Tissue Engineering - 2010
An interdisciplinary team of researchers from the Massachusetts General Hospital, Harvard Medical School and MIT were awarded by the American Bronchoesophalogical Association for the development of an injectable synthetic implant aimed at restoring vibratory function to damaged vocal cords. The new material is biocompatible with vocal fold tissue and has the requisite mechanical properties to facilitate vocal fold vibration. This implant has the potential to restore vocal function to millions of patients who have lost the ability to produce normal voice and speech.
Speech Communication - 2004
Dr. Frank Guenther and colleagues at Boston University are developing DIVA, a neural network model of the brain processes underlying speech production and perception. In computer simulations, DIVA learns to control the movements of a virtual vocal tract in order to produce speech sounds. The model accounts for a large number of speech production phenomena, and can be used to help determine the neural bases of various communication disorders.
Biophysics - 2003
Dr. Christopher Shera is using mathematical models to understand how the inner ear processes, amplifies, and creates sounds. His research has revolutionized understanding of these processes in the field of cochlear mechanics - one of his findings demonstrates that the cochlea acts as a biological analogue of a laser oscillator. Clinical application of this research is leading to better noninvasive tests of infant hearing.
Genetics of Hearing - 1999-2010
Hearing loss is influenced by genetics whether inherited from our parents or changes early in development. By exploring rare genetic rearrangements early in development, Dr. Cynthia Morton and colleagues at Brigham and Women’s Hospital have been able to identify several genes involved in hearing. These genes are involved in many diverse roles including structure, regulation, and metabolism.
Neuroscience - 2010
SHBT student Brad Buran, working in the laboratory of Dr. Charles Liberman at MEEI, showed that the temporal precision with which the auditory nerve conveys fine timing of acoustic signals to the brain relies on the synaptic ribbon, a complex structure located within the sensory cell at its synapse with the auditory nerve terminals. The ribbon functions to tether a population of “readily releasable” packets of neurotransmitter in close proximity to the synaptic membrane.
Neuroscience - 2002
Dr. Bertrand Delgutte and co-workers discovered that the envelope of speech signals is most important for conveying word meaning, while the fine structure is important for pitch and sound localization. To do this research they devised 'chimeric' sounds, which combine features of two different speech sounds into one. This finding may indicate that our brains process the meaning of sounds separately from their locations in space. It also has direct relevance for improving cochlear implant technology.
Biomedical Imaging - 2006
SHBT graduate Irina Sigalovsky, Dr. Jennifer Melcher and their colleagues at the Martinos Imaging Center developed a technique for localizing primary auditory cortex in people using structural MRI. The method measures the amount of myelin within the gray matter of the cerebral cortex. Spatially mapping gray matter myelination over the cortical surface revealed a "hot spot" of especially heavy myelination on the superior temporal lobe corresponding to the projections between auditory thalamus and primary auditory cortex. This was the first demonstration of a marker for primary auditory cortex in individuals.
Molecular Biology - 2002
Humans can hear sounds that move the eardrum less than the size of a hydrogen atom. Using transgenic mice, a multi-university research team co-led by Dr. Charles Liberman demonstrated that prestin, a newly identified protein, is the molecular motor responsible for the thousand-fold amplification of sound-induced vibrations by the sensory cells in the inner ear. This result was a important step in piecing together the molecular mechanisms underlying the remarkable sensitivity of hearing.
Development and Genetics - 2010
The Goodrich laboratory has recently completed a large scale analysis of genes expressed in inner ear neurons in mice. We documented gene expression in the neurons for hearing and balance from the earliest stages of axon guidance on through the onset of hearing. These data are publicly accessible through an online, searchable database on the laboratory website.
Neural Prostheses - 1997
Dr. Robert Hillman leads a research team that is developing an improved voice prosthesis to benefit the thousands of individuals worldwide who have lost the ability to produce voice and speech due to severe laryngeal dysfunction or surgical removal. The project has many innovative elements, including the construction of new sound sources, development of signal processing approaches, and precise hands-free pitch control via electromyographic signals to produce a more natural-sounding voice.
Treatment of Deafness - 2011
Dr. Steven Rauch and collaborators at 15 other medical centers have recently published results of a 6-year clinical trial comparing oral to intratympanic steroid treatment for sudden deafness. The study demonstrates that the two treatment have equal effectiveness but significantly different side effects and cost. These findings will likely lead to changes in clinical prescribing practices
Neural Prostheses - 1991
Dr. Donald Eddington played a key role in a cross-institutional team to develop a new speech processing strategy for cochlear implants. This strategy led to significant improvement in speech reception for implant users and has been widely applied in the industry ever since.
Neuroimaging - 2011
Dr. David Gow and colleagues recently developed a new way to combine different brain imaging techniques and examine how different parts of the brain influence each other while both healthy adults and people with brain damage perform tasks like recognizing speech sounds. Using this method they have found evidence for direct motor influence on speech perception, and lexical influences on phoneme categorization.
Neuroscience - 2005
Michale Fee studies how the brain learns and generates complex sequential behaviors, using the songbird as a model system. Birdsong is a complex behavior that young birds learn from their fathers and it provides an ideal system to study the neural basis of learned behavior. Because the parts of the bird's brain that control song learning are closely related to human circuits that are disrupted in brain disorders such as Parkinson's and Huntington's disease, Fee hopes the lessons learned from birdsong will provide new clues to the causes and possible treatment of these conditions.
Neuroimaging, Development Disorders - 2010
Dr. Maria Mody and her colleagues at the MGH Martinos Center have shown differences in brain activation and connectivity between normally developing and children diagnosed with dyslexia and autism despite similar behavioral performance, thus providing crucial evidence in support of core deficits in the verbal domain, with potential use as neural signatures of these disorders.
Biomedical Imaging - 1990s
Dr. Dennis Freeman and colleagues developed a laser-optical system for measuring sound-induced motions in the inner ear. The exquisite sensitivity of the cochlea to submolecular motions necessitated a system with unprecedented accuracy; this system is now being used in microlithography with the goal of manufacturing the next generation of computer chips.
Neuroscience - Mid 20th century
Hearing research has long been at the forefront of neuroscience, particularly at its interface with technology. Auditory neuroscientists were the first to use computers in neurophysiology (1959), to use glass microelectrodes to record from single neurons (1943), to use digital technology for stimulus synthesis (1959), to use correlation techniques for neural system identification (1963), and to propose a neural architecture that performs a specific computation (1951). Many of these firsts occurred at Harvard and MIT.