Long-duration low-level (LDLL) noise exposures can enhance or depress sound-evoked activity in the auditory cortex (AC), but it?s unclear if these neuroplastic changes originate in the AC or are inherited from lower levels of the auditory pathway. To address this, recordings will be obtained from the cochlea, inferior colliculus (IC) and AC to determine the magnitude and direction of change. To determine if LDLL noise exposures disrupt the neural input to the central auditory pathway, we will evaluate the inner hair cell pre- synaptic ribbons and key proteins expressed on the post-synaptic type I afferent fibers. Our working hypothesis is LDLL noise exposure depresses the neural output of the cochlea, but the central auditory pathway compensates for this by enhancing neural gain at progressively higher levels of the auditory pathway.
Long-duration, low-level (LDLL) noise exposure can result in a temporary threshold shift and functional changes in central auditory structures. The goals of this project are to determine if LDLL noise: 1) alters inner hair cell pre-synaptic ribbons or post-synaptic receptors on type I auditory nerve fibers and 2) changes the neurophysiological gain (i.e., response amplitude) along the auditory pathway (cochlea, inferior colliculus and auditory cortex) to compensate for a diminished neural output from the cochlea. The proposed studies will provide novel insight on how prolonged exposure to low-level noise affects the peripheral and central auditory systems.
| Zhao, Deng-Ling; Sheppard, Adam; Ralli, Massimo et al. (2018) Prolonged low-level noise exposure reduces rat distortion product otoacoustic emissions above a critical level. Hear Res 370:209-216 |
| Sheppard, Adam; Liu, Xiaopeng; Ding, Dalian et al. (2018) Auditory central gain compensates for changes in cochlear output after prolonged low-level noise exposure. Neurosci Lett 687:183-188 |
| Sheppard, Adam M; Zhao, Deng-Ling; Salvi, Richard (2018) Isoflurane anesthesia suppresses distortion product otoacoustic emissions in rats. J Otol 13:59-64 |
| Sheppard, Adam M; Chen, Guang-Di; Manohar, Senthilvelan et al. (2017) Prolonged low-level noise-induced plasticity in the peripheral and central auditory system of rats. Neuroscience 359:159-171 |
| Chen, Guang-Di; Manohar, Senthilvelan; Salvi, Richard (2012) Amygdala hyperactivity and tonotopic shift after salicylate exposure. Brain Res 1485:63-76 |
