Figure 6. A network of excitatory units with shared inhibition exhibits variable-speed sequences.

(a) A network of $N$ excitatory units are connected by self-excitation, feedforward excitation, and shared inhibition. (b) Just as in the recurrent inhibitory network, this network exhibits sparse sequential firing when the excitatory synapses are made depressing, with the speed of the sequence controlled by the level of external input. Parameters are ${\displaystyle \beta =0.2,{\tau }_y=20\tau ,{\tau }_I=\tau ,J^{\mathrm{E}\mathrm{I}}=J^{\mathrm{I}\mathrm{E}}=1,J_{ij}=0.6{\delta }_{ij}+0.2{\delta }_{j+1,j}}$.

DOI: http://dx.doi.org/10.7554/eLife.26084.007