In this text, the authors recall the main principles and data ruling cochlear implants. Then, a first circle of technical equipment for assistance is presented. This circle includes: device setting (DS), Electrically evoked Auditory Brainstem Responses (EABR), Neural Response Telemetry (NRT), Stapedial Reflex (SR) and Electrodogram Acquisition (EA). This first cycle becomes more and more important as children are implanted younger and younger; the amount of data available with this assistance makes necessary the use of models (implicit or explicit) to handle this information. Consequently, this field is more open than ever.1 Introduction1 1.1 About Hearing Mechanisms The hearing function in human beings is something very specific and difficult to understand because it uses the brain highest functions. Basically, we can say (figure 1) that several stages are involved [1]: It is not easy to give a unique interpretation to each one of these stages, as most of the involved processes overlap at all levels. Nevertheless, as a brief summary, let us assume that [2]: l The ear transmits the air vibrations and transforms them into electric stimuli compatible with nerve excitation, l Auditory pathways carry the electric pulses; exchanges take place, through decussation and information goes up using left and right channels. Also, specific features in the signal are detected and encoded before reaching the brain (phonetic features), l Brain interpretation matches input cues with the previously stored data into the memory and make association at different levels of language. In this text, we will come back on some ear features, mostly on the transformation of acoustical vibrations into electrical information transmitted to the brain. We will focus on the technical circle, but people fitted with a cochlear implant (CI) must be seen at all levels of language [3] and a typical team is composed of: l a E.N.T. (Ear Nose Throat) practitioner, l the surgeon performing the implantation, l a psychologist (a strong will and a good surrounding will favour good results), l a speech therapist, because the patient must be evaluated and taught the new language he has to adapt with, l an audiologist who have to set the implant and to take care of the technical details, l a manufacturer contact as modifications and improvement must be passed to the team, and, also, assistance may be needed, l a research group because this technique is under deep scrutiny, l some financial structure, as implants are not free. Cochlear implant is a multidisciplinary science and one must keep it in mind in order to understand the gist of this subject. 1.2 Electrical Rehabilitation Conversion of acoustical vibration into electrical stimulus takes place in the ear, and specifically in the inner ear. The organ of Corti is in charge of this transformation. In the organ of Corti, the inner hair cells (IHC) are moved toward a membrane (the membrana tectoria) and the hair is bent. IHC discharge toward the auditory nerve ends and the stimulus is carried toward the brain [4]. Obviously, when the organ of Corti is destroyed, a total cophosis takes place, and it becomes useless to amplify the signal as no conversion will occur. To beat this handicap, William House and Blair Simmons had, in the sixties, the idea to replace the organ of Corti by a direct electrical stimulation delivered by an electrical device. CI general organisation is indicated on figure 2. Acoustical Wave Ear Auditory Pathways Brain Interpretation Message Figure 1 Main stages of hearing Acoustical Vibration Speech Processor Transmission Cochlear Implant Distribution to Nerve Ends Figure 2 General organisation of a cochlear implant
