Electrical stimulation of the dorsal cochlear nucleus induces hearing in rats

Auditory brainstem implants (ABIs) restore hearing by electrical stimulation of the cochlear nucleus (CN). Depending on the physiological condition, duration of the pre-existing deafness, extent of damage to the CN, and the number of channels accessible to the tonotopic frequency gradients of the CN, ABIs improve speech understanding to varying degrees. Although the ventral cochlear nucleus, a mainstream auditory structure, has been considered a logic target for ABI stimulation, it is not yet clear how the dorsal cochlear nucleus (DCN) contributes to patients' hearing during ABI stimulation. To better understand the mechanisms underlying ABIs, we tested if electrical stimulation of the rat DCN induces hearing using a novel electrical prepulse inhibition (ePPI) of startle reflex behavior model. Our results showed that bipolar electrical stimulation of all channels in the DCN induced behavioral manifestation of hearing and that electrical stimulation of certain channels in the DCN induced robust neural activity in auditory cortex channels that responded to acoustic stimulation and demonstrated well-defined frequency tuning curves. This suggests that the DCN plays an important role in electrical hearing and should be further pursued in designing new ABIs. The novel ePPI behavioral paradigm may potentially be developed into an efficient method for testing hearing in animals with an implantable prosthesis.