Undifferentiated human ESCs (H1, WiCell) were maintained in mTESR (Stemcell Technologies) on matrigel (BD Biosciences)-coated plates. We did not authenticate this line, though we did conduct pathogen testing Colonies were dissociated with Dispase solution (Thermo-Fischer) and replated onto matrigel-coated plates at ~15% confluence. Induction of neural progenitors was adapted from Maroof et. al. 2013. On D0, hESCs were dissociated into a single cell suspension with Accutase (Life Technologies) and plated onto matrigel-coated 24-well plates at 3 × 105 cells/cm2 in mTeSR media with 2 μM thiasovivin (StemRd). Neural/telencephalic induction was initiated on D1 by replacing medium with NIMX (all reagents from Thermo Fisher Scientific unless indicated), a dual SMAD inhibition medium consisting of DMEM/F12, 1X N-2 supplement, 1X B-27 supplement, 2mM Glutamax Supplement, 0.1 mM MEM Non-Essential Amino Acids Solution, 0.11 mM 2-mercaptoethanol, 0.05% (v/v) Bovine Albumin Fraction V Solution, Penicillin-Streptomycin, 100 nM LDN193189 (Reagents Direct), 10 μM SB431542 (StemRD), 2 μM XAV939 (TOCRIS bioscience). Medium was changed daily. On D5, the medium was replaced with 75% NIMX media, 25% N2 medium (DMEM/F12 (1:1), N-2 supplement, 25% (w/v) dextrose (Sigma
