Local inhibitory Parvalbumin (PV)-expressing Basket cell networks shift to one of two possible opposite configurations depending on whether behavioral learning involves acquisition of new information or consolidation of validated rules. This reflects the existence of PV Basket cell subpopulations with distinct schedules of neurogenesis, output target neurons and roles in learning. Plasticity of hippocampal early-born PV neurons is recruited in rule consolidation, whereas plasticity of late-born PV neurons is recruited in new information acquisition. This involves regulation of early-born PV neuron plasticity specifically through excitation, and of late-born PV neuron plasticity specifically through inhibition. Therefore, opposite learning requirements are implemented by distinct local networks involving PV Basket cell subpopulations specifically regulated through inhibition or excitation. (C) 2015 Elsevier Inc. All rights reserved.