Figure 1.

The noise exposure used here creates a reproducible and uniform pattern of synaptopathy, as demonstrated in prior confocal studies. (A) Counts of synapses per IHC at 8 cochlear locations, in control mice (n = 16) vs. those examined 1 day (n = 10) or 1 week (n = 10) after synaptopathic exposure in a prior study². Mean values (± SEMs) were extracted from sets of confocal z stacks, each spanning 200 mm (~ 20 IHCs). Arrow indicates the 32 kHz region. (B) From the 32-kHz region in this prior confocal data, we extracted the number of synapses per 20 mm, i.e. the approximate span of the FIB-SEM stacks in the present study (also at 32 kHz). Each filled circle represents a different 20 mm sample. The asterisks show the synaptic counts extracted from each of the four FIB-SEM stacks in the present study, and stars indicate the total number of ANF terminals in each stack: both numbers were adjusted in proportion to the extent to which the stack span differed from exactly 20 mm. (C) A maximum projection of part of a confocal z-stack of the type used to extract the values in (A,B). Synapses appear as closely juxtaposed red and green puncta.