Experience reshapes cortical circuits, yet plasticity is tightly gated—high during early critical periods and increasingly constrained with maturation. Later in life, aging and Alzheimer’s disease (AD) create a growing demand to restrain network hyperactivity. Across these contexts, excitatory drive onto parvalbumin-positive fast-spiking interneurons (PVs)—shaped by synaptic organizers such as NPTX2—offers a control point for tuning inhibitory tone while preserving fast, precise inhibition. We o