Fig. S9.

Multielectrode recording of hippocampal culture. (A) Microscope image of 12 of 60 electrodes in 14 DIV hippocampal culture. The spacing between electrodes is 200 μm, and each electrode is 30 μm in diameter. (B) Overlay of all spike waveforms detected during a measurement of 1,800 s in each of the 55 active electrodes in this MEA. All electrode amplifier channels (ch) were recorded simultaneously, and the ongoing spike detection was based on the signal-to-noise ratio measured at each of the electrodes separately. The sampling rate was 13 kHz, and the x axes are given in units of the sampling points, showing a total of 26 sampling points, equivalent to 1 ms before and 1 ms after spike detection. The y axes are given in microvolts.