Sensitivity of spiking activity to mild mechanical perturbation (movement of the culture dish). A Number of bursts in first minute after culture was moved into the recording device, normalized to burst rate 10–30 minutes later. B Mean ASDR in first minute after culture was moved into the recording device, normalized to ASDR 10–30 minutes later. C Example of mechanically-induced bursting, recorded at 8 div from a dense culture. Gray scale is as in Figure 1. Lines are interpolations of the data, using a Gaussian window with a half-width of 1 day.