resting potential of the cell (applying 20 pA steps for 200 ms). Series resistance was monitored throughout the recording and was <20 MΩ. NBQX (25 μM, Tocris) and D-AP5 (50 μM, Tocris) were used to inhibit AMPA-receptor mediated and NMDA-receptor mediated excitatory synaptic responses, respectively. TTX (1 μM, Alomone) was used to block voltage-gated Na+ currents and record mEPSCs. An Axopatch 200A amplifier (Molecular Devices) was used for voltage and current clamp, and electrode junction potentials were compensated. Data were sampled at 50 kHz and filtered at 1 kHz using pClamp 9.2, and offline analysis was performed using Clampfit 10.3 (Molecular Devices). All electrophysiological experiments were performed between day 90 and 130 of in vitro differentiation.
