We used a previously published and extensively studied model of the DG that contains morphologically realistic models of the predominant cell type, granule cells, and other excitatory and inhibitory neurons.24- 26 The network consisted of 500 granule cells, 6 basket cells, 15 mossy cells, and 6 hilar perforant-path associated cells (HIPP). Granule and mossy cells are excitatory (α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate [AMPA] transmission), while basket and HIPP cells are inhibitory (transmission to γ-aminobutyric acid [GABA] type A receptors). Neuron models had between 9 and 17 compartments describing the dendritic arbor and realistic conductances including the fast sodium and potassium channels that directly form the action potential, an A current, L-, N-, and T-type calcium channels, hyperpolarization-activated, cyclic nucleotid-gated (HCN) current, and slow-voltage and calcium-gated potassium channels. Network connectivity is as follows: each HIPP cell contacts 160 granule cells, 4 mossy cells, and 4 basket cells. Each basket cell contacts 100 granule, 3 mossy, and 2 other basket cells. Each mossy cell contacts 200 granule, 3 other mossy, 1 basket, and 2 HIPP cells. In the absence of mossy fiber, sprouting granule cells contact 1 mossy, 1 basket, and 3 HIPP cells. In networks with mossy fiber, sprouting granule cells make spatially localized contacts with other granule cells (Figure 1). The degree of mossy fiber sprouting is quantified as a percentage, with 100% corresponding to 100 connections from each granule to other granule cells.24 Mossy fiber connections were generated randomly for each run.