Cochlear implant compression mimics cochlear mechanics and can test efferent function
Evidence
A direct demonstration would require being able to selectively deactivate the MOCR while keeping afferent auditory nerve fibres functional. To our knowledge, such an experiment has not been possible for human subjects up until now. Here, we argue that the experiment can be done in an approximate manner using cochlear implants (CIs). Cochlear implants can enable useful hearing for severely to profoundly deaf persons by bypassing the cochlea via direct electrical stimulation of the auditory nerve. The sound processor in a CI (Fig. 1 ) typically includes an instantaneous back-end compressor in each frequency channel of processing to map the wide dynamic range of sounds in the acoustic environment into the relatively narrow dynamic range of electrically evoked hearing (Wilson et al. 1991 ). The compressor in a CI serves the same function as the cochlear mechanical compression in a healthy inner ear (Robles and Ruggero 2001 ). In the fitting of modern CIs, the amount and endpoints of the compression are adjusted for each frequency channel and its associated intra-cochlear electrode(s). The compression once set is fixed. Cochlear implant users thus lack MOCR effects, but these effects can be reinstated, and thus the role(s) of the MOCR in hearing can be assessed by using dynamic rather than fixed compression functions. — Dijk, Pim van, Physiology, Psychoacoustics and…, 1940
Categorization
- XREF: CI back-end compressor as functional substitute for cochlear mechanical compression parallels how models stand in for unavailable physiological variables.
- SEED: An experimental-design essay: using implant dynamic compression as a ‘switch’ to selectively toggle an absent reflex in humans - a natural experiment unavailable in normal hearing.
- corroborated: 2 independent passages support this claim — Dijk, Pim van, Physiology, Psychoacoustics and…, 1940