RT Journal Article SR Electronic T1 Wiring variations that enable and constrain neural computation in a sensory microcircuit JF bioRxiv FD Cold Spring Harbor Laboratory SP 097659 DO 10.1101/097659 A1 William F. Tobin A1 Rachel I. Wilson A1 Wei-Chung Allen Lee YR 2017 UL http://biorxiv.org/content/early/2017/01/02/097659.abstract AB Neural network function can be shaped by varying the strength of synaptic connections. One way to achieve this is to vary connection structure. To investigate how structural variation among synaptic connections might affect neural computation, we examined primary afferent connections in the Drosophila olfactory system. We used large-scale serial section electron microscopy to reconstruct all the olfactory receptor neuron (ORN) axons that target a left-right pair of glomeruli, as well as all the projection neurons (PNs) postsynaptic to these ORNs. We found three variations in ORN→PN connectivity. First, we found a systematic co-variation in synapse number and PN dendrite size, suggesting total synaptic conductance is tuned to postsynaptic excitability. Second, we discovered that PNs receive more synapses from ipsilateral than contralateral ORNs, providing a structural basis for odor lateralization behavior. Finally, we found evidence of imprecision in ORN→PN connections and show how this can diminish network performance.