TY - JOUR TI - EM connectomics reveals axonal target variation in a sequence-generating network AU - Kornfeld, Jörgen AU - Benezra, Sam E AU - Narayanan, Rajeevan T AU - Svara, Fabian AU - Egger, Robert AU - Oberlaender, Marcel AU - Denk, Winfried AU - Long, Michael A A2 - Svoboda, Karel VL - 6 PY - 2017 DA - 2017/03/27 SP - e24364 C1 - eLife 2017;6:e24364 DO - 10.7554/eLife.24364 UR - https://doi.org/10.7554/eLife.24364 AB - The sequential activation of neurons has been observed in various areas of the brain, but in no case is the underlying network structure well understood. Here we examined the circuit anatomy of zebra finch HVC, a cortical region that generates sequences underlying the temporal progression of the song. We combined serial block-face electron microscopy with light microscopy to determine the cell types targeted by HVC(RA) neurons, which control song timing. Close to their soma, axons almost exclusively targeted inhibitory interneurons, consistent with what had been found with electrical recordings from pairs of cells. Conversely, far from the soma the targets were mostly other excitatory neurons, about half of these being other HVC(RA) cells. Both observations are consistent with the notion that the neural sequences that pace the song are generated by global synaptic chains in HVC embedded within local inhibitory networks. KW - connectomics KW - neural sequences KW - zebra finch KW - birdsong KW - synfire chains JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -