Four adult users of the House/3M single-channel cochlear implant were tested for their ability to label question and statement intonation contours (by auditory means alone) and to identify a set of 12 intervocalic consonants (with and without lipreading). Nineteen of 20 scores obtained on the question/statement task were significantly better than chance. Simplifying the stimulating waveform so as to signal fundamental frequency alone sometimes led to an improvement in performance. In consonant identification, lipreading alone scores were always far inferior to those obtained by lipreading with the implant. Phonetic feature analyses showed that the major effect of using the implant was to increase the transmission of voicing information, although improvements in the appropriate labelling of manner distinctions were also found. Place of articulation was poorly identified from the auditory signal alone. These results are best explained by supposing that subjects can use the relatively gross temporal information found in the stimulating waveforms (periodicity, randomness and silence) in a linguistic fashion. Amplitude envelope cues are of significant, but secondary, importance. By providing information that is relatively invisible, the House/3M device can thus serve as an important aid to lipreading, even though it relies primarily on the temporal structure of the stimulating waveform. All implant systems, including multi-channel ones, might benefit from the appropriate exploitation of such temporal features.

A percutaneous connector system has been developed for use in neural prosthetic applications. It is based on a skin-penetrating, bone-anchored titanium pedestal, housing an 11-channel electrode array. Initial applications for the system are in audiology and, as such, the proposed fixture site is in the temporal bone. The titanium pedestal is based on existing design features of the EPI Bioglass® implant, developed by University College London (UCL), and the Brånemark System®, employed by Nobel Biocare AB. The electrode array, consisting of platinum wires in a silicone carrier, can be custom designed to suit the application. The design features of the connector system are reviewed. Animal studies have been used to assess soft tissue reactions and the osseointegration of the pedestal. The histological data are presented. The pedestal, electrode array and the mating external connector are currently undergoing mechanical and electrical testing. The percutaneous connector system will undergo clinical trials, initially in the study of tinnitus (employing stimulation via an extracochlear electrode), and as part of a cochlear implant system (using a multichannel intracochlear electrode array and digital signal processing techniques).

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Chronic electrical stimulation of the auditory nerve in patients with profound sensori-neural deafness is becoming increasingly routine. Therefore, it is important to understand more about the long-term consequences of this procedure. Hitherto, structural studies in animals after electrocochlear stimulation have concentrated on the stimulated cochlea. Here we have examined the effects of unilateral extracochlear electrical stimulation on the spiral organ of both the ipsilateral and contralateral ears of the mature guinea pig, and have found alterations in the structure of the outer hair cells and their efferent nerve terminals in the contralateral as well as the ipsilateral cochlea. This is the first evidence for a structural influence of efferent activity on the cochlea. Although the importance of the efferent system, consisting of the crossed and uncrossed olivo-cochlear bundles, is well established in providing central control of the sensory pathways, its exact role in hearing is incompletely understood. However, it is known that the outer hair cells and their efferent innervation are important in their contribution to inner hair cell responses and in modulating the micromechanics of the whole cochlea. These efferent functions now appear to be related to an important part of cochlear morphology, and are also relevant to our understanding of cochlear neurobiology, normal development and the management of hearing disability in both adult and child.