Spontaneous network activity of cortical neurons in culture. A, Distribution of basal burst rates (n = 65). Bars represent the number of recordings within individual 0.05 Hz bins. The distribution was well fitted by a single Gaussian function (black line; R² = 0.77). B, Sample traces illustrating synchronous spontaneous bursting (upper panel). Application of NBQX and AP5 abolished network bursting (lower panel). C, Higher-resolution traces illustrating the network burst framed in B. D, Summary graph of the effect of NBQX + AP5 (n = 4) and of TTX (n = 4) on spontaneous network bursting.