Christoph Borgers

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  Suppression boundaries in E-I networks, and the type of the I-cells
  Christoph Borgers

  The synaptic interaction of excitatory and inhibitory neurons (E- and I-cells) can generate oscillations, provided that the drive to the I-cells is low enough, so that they don't get ahead of the E-cells but merely respond to them. If the drive to the I-cells is high, and inhibitory synapses are strong, the E-cells are suppressed altogether. We think about the transition from rhythmicity (low drive to the I-cells) to suppression of the E-cells (high drive to the I-cells). In work with Nancy Kopell several years ago, we suggested that this transition, if it is abrupt, could be exploited to allow the network to toggle between rhythmic activity and suppression, and that this could be useful in attentional selection. In contrast with the earlier work, here we assume that synchronization of the I-cells is always enforced by gap junctions. We find that in this case, the transition from rhythmicity to suppression is much more abrupt when the I-cells have a type 2 phase response (excitation early in the phase retards them) than when they have a type 1 phase response (excitation always accelerates them). We demonstrate this with simulations and explain it using a one-dimensional map.