A,B: Electron micrographs of endbulb of Held (EB) profiles (yellow) contralateral to the cochlear implant placed in a 6-month-old congenitally deaf cat. A′,B′: The 3-D reconstructions show that there is no effect on the PSDs from the late implanted cochlear implant. The red areas indicate sections of the EB series that are shown in the electron micrographs, and the horizontal lines indicate section edges. SBC, spherical bushy cell. Scale bar = 0.5 μm in B (applies to A,B) and B′ (applies to A′ and B′).