to evaluate the maturation of the hESC-derived hippocampal neural networks at 3 weeks and 6 weeks postdifferentiation. We observed a significantly increased percentage of active neurons as well as a higher frequency of calcium transients at 6 weeks versus 3 weeks postdifferentiation, indicating maturation of the neuronal population and increased levels of network activity (Figure 4B). These intracellular calcium transients could be blocked by the Na+ channel blocker tetrodotoxin (TTX), verifying its correlation with neuronal activity (Figures 4C, 4D, and 4H).
