supplemented with B27 and L-glutamine. Doxycycline (2 ng/μl) was added on Day 1 to induce expression of subtype-specific transcription factors, along with Y-compound (5 μM) to limit apoptosis. On Day 2, iPSCs underwent a puromycin (1 μg/ml) selection. Day 3 cultures underwent additional puromycin selection with addition of secondary viral vectors as needed. Channelrhodopsin 2 (ChR2)-tdTomato lentivirus was added to excitatory neurons on Day 3 as necessary. Inhibitory neurons underwent an additional hygromycin (25 ng/ml or higher as needed) selection on Days 3 and 4 prior to seeding into the device. iNs were kept in Neurobasal media with L-glutamine, B27, doxycycline and puromycin (hygromycin also for inhibitory iNs) until plated on Day 6.
