Feasibility Experiments For The Development Of A Midbrain Auditory Prosthesis

This paper presents a new approach for hearing restoration in patients suffering from sensorineural hearing loss. We focus on the development of a midbrain auditory prosthesis, implanted into the central nucleus of the inferior colliculus (ICC). We performed experiments in a guinea pig model to initially explore the tonotopic map that exists between ICC and the primary auditory cortex (A1), the initial center for auditory perception. Using multichannel electrodes, we were able to stimulate along 16 different ICC sites and simultaneously record from 16 different A1 sites. Both electrodes were placed along similar tonotopic gradients. ICC stimulation in low frequency regions induced activity in low frequency regions of A1, and similar trends were seen for higher frequencies. ICC stimulation appears to be very specific, causing minimal spreading of activity across A1 sites, and stimulation threshold levels were significantly lower than that currently obtained using cochlear prostheses. These results indicate that an ICC-based auditory implant may provide a more focused means of stimulation at lower threshold levels for hearing restoration compared to current cochlear prostheses. The tonotopic map between ICC and A1 suggests that a frequency-place code may be utilized in a midbrain auditory prosthesis.