Loss of efferent innervation, whether by OC lesion or chronic conductive hearing loss, compresses the spatial distribution of afferent synapses (A,B), and inner hair cells (C), along the modiolar-pillar axis; the staggered packing of adjacent hair cells, which arises from hair cell hypertrophy, is normally maximal (C) at cochlear locations where the LOC innervation is densest (D).

<p>A,B: Spatial distribution of inner hair cell afferent synapses along the modiolar-pillar axis for each experimental groups compared to age-matched controls. Synaptic location is defined as described in Methods. Mean values are shown for each group within each 1-μm location bin. Data are combined across all cochlear locations. C: Staggering of the inner hair cell row was quantified by measuring the nuclear spread (see schematic in E), as seen in yz projections of confocal z-stacks (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0142341#pone.0142341.g005" target="_blank">Fig 5</a>). Mean values (±SEMs) are shown. D: Mean density of LOC innervation (±SEMs) in age-matched control ears as a function of cochlear location. Symbol keys in A,B also apply to C,D. E: Schematic illustrating the staggered positioning of inner hair cell nuclei along the modiolar pillar axis, and the measure of “nuclear spread” used to quantify it.