Neuronal networks derived from hESCs and hiPSCs were infected with the Synapsin-DsRed lentiviral vector. Cell cultures were incubated with 2–5 μM Fluo-4AM (Molecular Probes/Invitrogen) for 40 min at room temperature. The threshold for activity was set at the 95th percentile of the amplitude for all detected events. Images were acquired with MetaMorph 7.7 (MDS Analytical Technologies) and processed using ImageJ (http://rsbweb.nih.gov/ij/) and custom-written routines in Matlab 7.2 (Mathworks).
