Figure 1
Location of the cochlear-implant electrode and the morphology of the porous modiolus. (a), Schematic cross-section of the cochlea, showing a cochlear implant (CI) inserted into one of the three fluid-filled canals, scala tympani (ST). The other two canals are called scala vestibuli (SV) and scala media (SM). The red rectangle, labelled EC, denotes one of the electrical contacts (or channels) comprising the CI. The CI stimulates the spiral ganglion neurons (SGNs), each of which, when intact, is comprised of a peripheral process (PP), a cell body called a spiral ganglion cell (SGC), and a central process (CP). The SGCs are located in a hollow, fluid-filled spiral canal called Rosenthal's canal (RC) that runs inside the porous bony modiolus, the cochlea axis. Two examples are shown of SGNs with intact peripheral processes (red SGCs), and two without (degenerated) peripheral processes (purple SGCs). Adapted with permission from Ref.5, their Fig. 2a. (b), Scanning electron microscopic (SEM) image of a cross-section of the lower basal turn of the human cochlea, with the schematic cross-section of a perimodiolar CI30 added into the image. Green: SGCs. Red: Auditory nerve fibres (also called peripheral axons or dendrites). Arrow: Mesothelial sheet guiding the dendrites through the osseous spiral lamina (*) to the SGCs. The dotted lines delineate the region used for modelling the electrical effects of modiolus porosity. Adapted with permission from Ref.7, their Fig. 18a.
