More than 8% of the French population suffers from hearing impairment (Rapport DRESS, 2007). Although the importance of this deficiency varies among individuals, it strongly increases after the age 40. With an aging population, the development of effective treatments of deafness has become increasingly important, and has already yielded both significant medical and technological advances. Depending on the severity of the handicap, different medical treatments can be applied to hearing‐impaired people.

                                                                                                

For severe to profound sensorineural hearing loss, cochlear implants (CIs) remain the only way to restore hearing sensations. CIs work by stimulating the auditory nerve electrically via surgically‐implanted electrodes. Worldwide, more than 300 000 people have been fitted with a CI during the last four decades. The success of this device in restoring speech perception has led to a relaxation of the criteria of candidacy for implantation.    

       

The number of CI users is, therefore, increasing rapidly, and there is a substantial international effort towards novel stimulation strategies to improve their perception of sounds. The present project forms part of this effort and aims (1) to refine our understanding of the basic principles of electrical stimulation of the auditory nerve, (2) to use this knowledge to optimize the stimulation parameters of existing implants, and (3) to develop innovative strategies to improve the coding of sounds transmitted by future generations of CIs.

It has long been shown that sequential stimulation of the electrodes reduces the amount of channel interactions compared to when electrodes are stimulated synchronously. Nevertheless, the excitatory effect a given electrical pulse has on the nerve fibers is strongly dependent on previous stimuli. 

These “sequential interactions” have several components which can be divided into subthreshold interactions (due to the integration of charge by the neurons before they reach their firing threshold), peripheral suprathreshold interactions (due to refractoriness and adaptation) and central suprathresholdinteractions (due to the integration/smoothing of neural activity more centrally).

                                                                                                                                       

About the laboratory             

The LMA is a research unit of the CNRS (UPR 7051) attached to the Institute of Engineering Sciences and Systems (INSIS) and bound by convention in the 2012-2016 five-year contact Aix-Marseille University (AMU) and Centrale Marseille (ECM).

It aims to ensure the continuum Fundamental Research Engineering Technology in its area of expertise; Acoustics and Solid Mechanics.

Cochlear Implant unit           

The DAIMA Research Unit working on cochlear implants is connected to auditory perception team of the LMA-CNRS laboratory.

We try to understand further the fundamental principles governing hearing using both acoustic stimulations in normal- hearing listeners and electic stimulations in cochlear implants users.

  Current members                  

Olivier Macherey (reseacher) 

Gaston Hilkhuysen (post-doc) 

Pierre Stahl (PhD) 

Quentin Mesnildrey (PhD) 

   Collaborations                       

Robert P. Carlyon -MRC Cognition and Brain Sciences Unit, Cambridge

Dr Stephane Roman - CHU La Timone, Marseille

Yves Cazal - LNIA, Saint Charles, Marseille

Arnaud Norena - LNIA, Saint Charles, Marseille

  Recent publications             

Optimizing Pulse-Spreading Harmonic Complexes to minimize intrinsic modulations after cochlear filtering (submitted to the Journal of the Acoutical Society of America)  Hilkhuysen. G.L.M. & O. Macherey