Figure 6

Extracellular electrophysiology of differentiated mDPSC. Twelve differentiated mDPSC cultures were assayed on MEAs and assessed for network activity. Ai) Differentiated mDPSC cultures exhibited numerous short, low amplitude events that surpassed a threshold of detection. These events were smaller and less numerous than those seen in mESC (Aii) and cortical (Aiii) cultures. B) A representative image of a central region of nine electrodes of a MEA with mDPSC at day 11 of differentiation. Electrode diameter is 30 μm. C) Maximum spike rate of mDPSC events within a 100 second bin was significantly lower than mESC and cortical signals and not distinguishable from PBS-only events. D) Boxplots of the mean amplitude of spike events. Spike amplitides were significantly lower in mDPSC cultures than control mESC or cortical cultures and were not significantly different from PBS-only control traces. E) A representative trace of a single oscillation event observed in a mDPSC MEA culture from day 32 of differentiation. The epicenter of oscillatory activity occurred at electrode 13 (e13, black) and was repeated at numerous adjacent electrodes, such as e23 (red), in phasic synchrony. A distant electrode, e75 (ii, blue), did not show any obvious oscillatory activity. F) The spectral power density of oscillatory activity in 6E reveals its broad frequency range peaking at 95 Hz that is consistent across the three representative electrodes shown. e13 (red) has the greatest intensity as observed visually followed by e23 and also e75 whose oscillations could not be detected by eye. **P <0.01, ***P <0.0001. ESC, muring embryonic stem cells; mDPSC, murine dental pulp stem cells; MEA, microelectrode array.