> With the implants though, they don't try to stimulate via > pressure, they just send electrical impulses through the > electrodes. The resulting electric

> With the implants though, they don't try to stimulate via > pressure, they just send electrical impulses through the > electrodes. The resulting electric field is what > stimulates the nerve. Yes, it is true that electrical stimulation skips a few steps in the signaling cascade, but I don't think that matters, in principle, since the end result for both cases is the generation of action potentials. In normal hearing, the pressure waves affect perception by mechanically deflecting the stereocilia (hairs) on the hair cells, which open ion channels, which lead to the production of action potentials. Electrical stimulation, on the other hand, opens the ion channels directly (either on the hair cells themselves or a synapse or two upstream), bypassing the mechanical action of the stereocilia entirely. This is actually a good thing since in sensorineural hearing loss it is often the hairs or hair cells that are damaged or malformed. By interfacing with the nervous system so peripherally, the vast majority of the neural processing in the auditory system is preserved, as opposed to auditory brainstem implant or stimulation of cortical auditory regions. Of course there are technical limitations to electrical stimulation: the spatial and temporal spread of the electric field is only a very rough approximation of the pressure waves caused by sound, even with sophisticated acoustic models of the cochlea. But with smaller electronics and increased numbers of channels it should be possible to make the match closer, and perhaps someday indistinguishable for most individuals. These are differences in degree not in kind.