Biophysical diversity amongst inner ear bipolar neurons

The cell bodies of vestibular and auditory ganglion neurons express a diverse range of ion channels and neurotransmitter receptors. This diversity provides a rich biophysical substrate for shaping the excitability of neurons and expands the populations’ repertoire for sensory signaling. In the vestibular nerve, the temporal precision needed to code rapid head movements is determined by neurons firing at irregular intervals whereas the ability to sensitively detect slow head movements is determined by neurons firing at regular intervals. I will describe recent work from my laboratory testing the idea that ion channels resident in the membranes of vestibular neurons are responsible for producing this diversity in spike-timing regularity. Our results suggest that definitive relationships between ion channel composition and neuronal function cannot be established without also considering the impact that efferent modulation has on individual ion channels. I’ll show that the role played by an ion channel can be context dependent; varying based on its density, and activation state, as well as on its interactions with other channels. I will end the talk by describing our recent work linking the ion channel properties of spiral ganglion neurons to sub-groups of Type I auditory afferents.