UC Berkeley

The auditory pathway has a remarkable ability to change its response based on sound experiences. Plasticity also occurs as an adaptive response following injury to the auditory pathway, such as in hearing loss. My doctoral work aims to improve our understanding of plasticity in the auditory system during normal development, and in cases of trauma or disease.

First, I studied the tonotopic map of the primary auditory cortex and inferior colliculus in juvenile rats that underwent passive exposure to a single frequency pure tone pip during the auditory critical period. Previously it has been shown that such acoustic exposure leads to an enlarged representation of the exposure frequency in primary auditory cortex. However, whether this change originated in cortex or also present in an upstream auditory nucleus remained unclear. I addressed this question by comparing the tonotopic representations of inferior colliculus and primary auditory cortex and showed that enlarged frequency representation is observed only in the primary auditory cortex but not in the inferior colliculus.

Second, I investigated adult plasticity following hearing loss. It has been hypothesized that a reorganization of auditory cortex underlies perceptual problems that develop after hearing loss. In particular, perception of a phantom sound, or tinnitus, has been associated with abnormal tonotopic representation in the auditory cortex. Using a mouse behavioral model of tinnitus, I have shown that tonotopic map reorganization is likely a consequence of hearing loss, and is not sufficient to induce tinnitus by itself. Further, I have provided evidence that changes in the Glutamate Decarboxylase 65 expression level may be involved in the etiology of tinnitus.