Coding of Speech Signals in the Human Auditory Nerve

inclusion criteria : Will be included as hearing impaired patients: * male or female * over 18 years of age * who are to undergo surgery on the cerebellopontine angle (microvascular decompression, vestibular neurotomy, removal of a meningioma or schwannoma tumor) * with a mild to severe sensorineural hearing loss defined by an average hearing loss (average of thresholds obtained at 500, 1000, 2000 and 4000 Hz) greater than 20 dB and less than 90 dB in pure tone bone conduction audiometry on the side of the operated ear. * affiliated to a social security system. * have read the information note describing the study and have agreed in writing to participate by signing the informed consent form. Will be included as normal hearing patients: * male or female * over 18 years of age * who are to undergo surgery in the cerebellopontine angle (microvascular decompression, vestibular neurotomy, removal of a meningioma or schwannoma tumor) * free of neuro-sensory deafness, defined by average hearing thresholds less than or equal to 20 dB in tonal bone conduction audiometry on the side of the operated ear * affiliated with a social security system. * having read the information note describing the study and having agreed in writing to participate by signing the informed consent form. exclusion criteria : Patients for whom the auditory nerve is not accessible during surgery, * because of a complete tumor invasion of the cochlear nerve (stage III and IV neuroma, advanced meningioma) * because of an anatomical feature not identified during the preoperative examination, making its exposure for recordings impossible (protrusion of the posterior face of the rock)