The MEA recordings were performed using the MEA-1060 system (Multichannel Systems, Reutlingen, BW, Germany). Before plating the cells, MEA dishes were sterilized by applying 70% ethanol and exposing to UV light for 120 min. Poly-D-lysine was used to hydrophilize and coat the surface of the MEA dishes. Laminin (Invitrogen/Thermo Fisher, Inc., Waltham, MA, USA) was also applied to the MEA surface (overnight at 37 °C) to promote cellular adhesion (to culture cells for > 10 days) and to increase the neural processes development. Human fetal brain cells were plated on MEAs (5000 cells/mm)2. After preparation, the suspended cells were placed onto the MEA dishes, settled, and adhered to the array within 4 h. Neurons were maintained and fed using an appropriate medium every 3 days with half media changes. MEA recordings were started when the cultures were 1, 3, and 4 weeks old. After placing the MEAs on the amplifier, recordings were performed using the MC Rack software (Reutlingen, BW, Germany) at a sampling frequency of 2000 kHz.
