Kavli Affiliate: Mark Ellisman
| Authors: George A. Spirou, Matthew Kersting, Sean Carr, Bayan Razzaq, Carolyna Y. Alves-Pinto, Mariah Dawson, Mark H. Ellisman and Paul B. Manis
| Summary:
Abstract Bushy neurons of the cochlear nucleus encode temporal fine structure and modulation of sound with high fidelity. However, the synaptic maps and electrotonic structures that underlie these properties are not specified in meaningful explanatory detail. We employed modern volume electron microscopy techniques to provide exact data on the numbers of synaptic inputs and their weights determined by the number of contained active zones, and the surface areas of all postsynaptic cellular compartments. Leveraging these high-resolution images, we discovered cabling of dendrite branches and new structures within dendrites, and identified non-innervated dendrites. We extend current nanoscale connectomic studies with methods to export cellular reconstructions into morphologically-constrained, biophysically-based predictive computational models. We reveal both coincidence detection and mixed supra/subthreshold modes of input convergence across the bushy cell population and show subthreshold inputs contribute to enhanced temporal encoding even in the presence of suprathreshold inputs. We demonstrate the variation of dendritic load and axon parameters and their importance in controlling excitability as potential homeostatic mechanisms, thereby defining heterogeneity in stimulus-evoked responses across the BC population. Competing Interest Statement George A. Spirou is the Chief Scientific Officer of IstoVisio, Inc., which makes the syGlass software used to visualize the EM volume and reconstruct the neurons. None of the other authors have competing interests to declare.