PVALB and Cognitive impairment: Changes in interneuron numbers have been widely implicated in a number of cognitive deficits [43], therefore we quantified cortical interneuron populations including parvalbumin (PV+; Fig. 5A, B), calretinin (CR+; Fig. 5C, D), and neuropeptide Y (NPY+; Fig. 5E, F) interneurons in EfnB1Y/+ and EfnB1Y/− mutants.