Figure 6.

Quantifying the temporal organization of Ca²⁺ spikes in spontaneously-oscillating IPS-CM clusters. (A) The inter-spike interval (ISI) and temporal heterogeneity index (THI) was calculated from Ca²⁺ signal traces obtained from each C-area. F.I. is fluorescence intensity of fluo-4. (B,C) The effect of EB age (B) and the time of subsequent “on plate” culture (C) on regional Ca²⁺ synchronization (upper panels), ISI (middle panels), and THI (lower panels) in post-EB IPS-CM clusters is plotted. Data from different times points of the protocol are color coded as shown and were fitted with least-squares polynomial equations. The correlation co-efficients (x²) and p-values are given in each instance.