Figure 4.

Time course of afferent innervation of newborn GCs. Schematic representation of monosynaptic inputs to the newborn GCs at time-points evaluated (21, 30, 60, and 90 days after retroviral infection). At 21 days (d), newborn GCs mainly receive connections from mature GCs. This input gradually shifts from mature GCs to cortex following strengthening of afferents from the perirhinal (PRH) and lateral entorhinal cortex (LEC). Increased hilar cell (mossy cells and interneurons) innervation is observed over time. Convergence of excitatory afferents onto the newborn GCs around 30 days correlates with transiently enhanced new neuron excitability and plasticity. Innervation from septum and area CA3 pyramidal cells (PYR) remains constant over time.