Research has demonstrated that chronic electrical stimulation of the cochlea can prevent the degeneration of the cochlear neurons that otherwise occurs as a consequence of deafness. Moreover, higher frequency, complex stimulation is more effective than low frequency signals in inducing these protective effects. Results indicate that the frequency organization of the central auditory system is relatively normal for many months after deafness occurring early in life. In contrast, chronic stimulation of a single channel of a cochlear implant causes marked expansion of its representation and consequent distortion in the frequency map . Parallel alterations in the temporal response properties to electrical stimulation also have been demonstrated.
Research continues on developing improved designs for multichannel cochlear implants.
In order to evaluate novel electrode designs, a clear plastic model of the human cochlea has been developed which contains a dimensionally accurate replica of the scala tympani. This research tool allows the surgeon or engineer to directly observe the insertion of cochlear implant electrodes, and to assess how the mechanical properties of the electrode might affect the safety and accuracy of surgical placement. The model is currently being used here at UCSF, and at several other cochlear implant research centers throughout the world, to develop improved electrodes, surgical techniques and instruments. Basic Anatomical and Developmental Studies of the Cochlea and Its Neural Projections to the Cochlear Nucleus . We have used a variety of electrophysiological, morphometric, ultrastructural and cytochemical labeling techniques to examine the detailed frequency organization of these projections.