Concurrent maturation of inner hair cell synaptic Ca2+ influx and auditory nerve spontaneous activity around hearing onset in mice

Aaron B. Wong, Zhizi Jing, Mark A. Rutherford, Thomas Frank, Nicola Strenzke, Tobias Moser

Research output: Contribution to journalArticlepeer-review

42 Scopus citations

Abstract

Hearing over a wide range of sound intensities is thought to require complementary coding by functionally diverse spiral ganglion neurons (SGNs), each changing activity only over a subrange. The foundations of SGN diversity are not well understood but likely include differences among their inputs: the presynaptic active zones (AZs) of inner hair cells (IHCs). Here we studied one candidate mechanism for causing SGN diversity- heterogeneity of Ca2+ influx among the AZs of IHCs- during postnatal development of the mouse cochlea. Ca 2+ imaging revealed a change from regenerative to graded synaptic Ca2+ signaling after the onset of hearing, when in vivo SGN spike timing changed from patterned to Poissonian. Furthermore, we detected the concurrent emergence of stronger synaptic Ca2+ signals in IHCs and higher spontaneous spike rates in SGNs. The strengthening of Ca2+ signaling at a subset of AZs primarily reflected a gain of Ca2+ channels. We hypothesize that the number of Ca2+ channels at each IHC AZ critically determines the firing properties of its corresponding SGN and propose that AZ heterogeneity enables IHCs to decompose auditory information into functionally diverse SGNs.

Original languageEnglish
Pages (from-to)10661-10666
Number of pages6
JournalJournal of Neuroscience
Volume33
Issue number26
DOIs
StatePublished - 2013

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