Figure 7. Young neurons destabilize network activity in the intact dentate gyrus.

a.) Schematic of the dentate gyrus, depicting effect of immature granule cells on correlated cell firing and gamma bursting activity. Left panel: in the presence of young adult-born granule cells (gray), the dentate gyrus shows only modest correlations of cell firing (purple somata) and smaller gamma bursts (example LFP at lower left). Right panel: after eliminating adult neurogenesis with X-irradiation, young neurons are no longer present and we observe increased correlations in cell firing and amplitude of gamma bursts. b.) Model of the effects of young neurons on dentate activity. We propose two possible explanations for the effects of immature adult-generated granule cells on neuronal phase locking to gamma bursts and gamma burst amplitude: 1.] (red) Immature granule cells may fire more easily, increasing the tone of feedback interneurons in the hilus that subsequently clamp down on gamma bursting activity. 2.] (yellow) Young neurons may compete for strong perforant path connections with mature cells, which normally drive gamma bursting events after barrages of entorhinal cortical input.