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Ryugo Lab - Auditory Anatomy & Physiology
Our long-term goals are to understand neuronal mechanisms that underlie hearing in mammals. In the auditory nervous system, all acoustic information from the environment enters the brain by passing through the auditory nerve and terminating in the cochlear nucleus. The cochlear nucleus serves as the gateway to the central auditory system because it gives rise to all ascending pathways. How auditory information is processed will depend greatly on the structural organization of auditory nerve inputs.
The relatively homogeneous responses of incoming auditory nerve fibers are transformed into a variety of different response patterns by the different classes of resident neurons in the cochlear nucleus. These signals are in turn transmitted to higher centers by the ascending pathways. The spectrum of the responses depends not only upon the synaptic organization of the auditory nerve but also on intrinsic neurons and descending inputs; the types and distribution of receptors, ion channels, and G proteins; and second messengers. These features form the signaling capabilities for each cell class. In order to understand how sound is processed, there is a need to study identified cell populations, to analyze their synaptic connections, and to reveal features of their signal processing capabilities.
Inner ear pathology (e.g., hair cell damage resulting in deafness) causes synaptic reorganization in the cochlear nucleus. Consequently, there may be additional abnormalities induced at higher auditory centers due to transneuronal influences. The cochlear nucleus is not only a key structure in normal hearing but also for the consequences of deafness. Our studies seek to provide new knowledge toward understanding basic mechanisms of hearing and the role of hearing in the development of the central auditory system.
Our Laboratory is an outstanding example of how discoveries in basic science alter and expand our knowledge base, generate new avenues of scientific inquiry and fundamentally influence how physicians think about the treatment strategies they offer to patients. For almost 20 years at Johns Hopkins, we have been pursuing the line of research that examines the effects of congenital deafness on the structural and functional development of the central auditory system. This is an enormous, fascinating and ongoing endeavor that would not be possible without external financial and philanthropic support.