Sensory Neurobiology Laboratory
Susan Shore, Ph.D., Laboratory Director
Photomicrograph of an octopus cell labeled after an injection of fluorescent tracer into the adjacent posteroventral cochlear nucleus during a tract-tracing experiment.
The objectives of this laboratory are to study the roles of neural connections from other parts of the brain to the auditory brain stem. A strong emphasis of our studies are two major projection systems: the somatosensory innervation to the external regions of the cochlear nucleus and inferior colliculus, and descending connections from other auditory structures to core regions of the cochlear nucleus. In addition to the normal innervation, we also study changes in these pathways after various forms of hearing loss, and their possible roles in tinnitus, loudness recruitment and central auditory processing.
The cochlear nucleus is an integrating center for auditory and non-auditory information. We have demonstrated that somatosensory neurons send synaptic terminals into the cochlear nucleus and when electrically stimulated, cause synaptic plasticity that is spike-timing dependent. After deafness, there is an increased number of glutamatergic somatosensory terminals in the cochlear nucleus that contribute to increased excitability of these neurons and may be one underlying cause of phantom sound perception or 'tinnitus'
We use tract-tracing and immuno-histochemical methods to study neural connections and single and multi unit neurophysiology to study the responses of neurons to sounds. The implementation of multichannel recording and drug-delivery electrodes expedites our studies of single cell responses. Lesion studies and neuropharmacology are used to assess the role of extracochlear pathways in sound coding.
The laboratory is funded by grants from the National Institutes of Health, Tinnitus Research Consortium(TRC), Royal National Institute for Deaf People (RNID), the Tinnitus Research Incentive (TRI) and American Tinnitus Association (ATA), University of Michigan Coulter Foundation.