hiPSC forebrain NPCs were derived as described previously.11 Forebrain NPCs were maintained at high density, grown on either Matrigel or poly-ornithine/laminin-coated plates in NPC media (Dulbecco's Modified Eagle Medium/Ham's F12 Nutrient Mixture, 1x N2, 1x B27-RA (Life Technologies, Carlsbad, CA, USA)), 1 μg ml−1 laminin (Life Technologies) and 20 ng ml−1 Fibroblast Growth Factor 2 (Life Technologies) and split ~1:3–1:4 every week with Accutase (Millipore, Billerica, MA, USA).
