An extensive neural network connects the auditory cortex downward to various parts of the peripheral auditory system. A portion of this neural network at the brainstem connects and reflexively affects outer hair cell activity in the cochlea thereby modulating cochlear gain. Cortical neural networks further influence the working of this reflexive neural mechanism providing cortical control of the peripheral hearing organ.
We study this network and its effect on cochlear gain using otoacoustic emissions and other tools. Much of this work is at the stage of basic discovery of the phenomenology at this time but we are actively interested in extending our understanding to useful tools to gauge the functional relevance of this neural network. We have published work on the speed of this process of gain control. Work to understand the frequency tuning properties of this system and the interaction between cortical and brainstem networks is ongoing and has already led to interesting (and bewildering) findings.
Funded by the Knowles Hearing Foundation.
1. W Zhao, JB Dewey, S Boothalingam, S Dhar (2015). Efferent Modulation of Stimulus Frequency Otoacoustic Emission Fine Structure, J Clin Sleep Med, 168. pdf
2. C Abdala, S Dhar, M Ahmadi, P Luo (2014). Aging of the medial olivocochlear reflex and associations with speech perception, J Acoust Soc Am, 754-765. pdf
3. JB Dewey, J Lee, S Dhar (2014). Effects of Contralateral Acoustic Stimulation on Spontaneous Otoacoustic Emissions and Hearing Threshold Fine Structure, J Assoc Res Otolaryngol, . pdf
4. W Zhao, S Dhar (2012). Frequency Tuning of the Contralateral Medial Olivocochlear Reflex in Humans, J Neurophysiol, 25-30. pdf
5. W Zhao, S Dhar (2011). Fast and slow effects of medial olivocochlear efferent activity in humans, PLoS One, e18725. pdf
6. W Zhao, S Dhar (2010). The effect of contralateral acoustic stimulation on spontaneous otoacoustic emissions, J Assoc Res Otolaryngol, 53-67. pdf