Development of burst patterns in a dense culture. Graphs show array-wide spike detection rates (ASDR) per second in recordings from one culture at various ages (numbers in top right corners). Note the different vertical scales used for each day. The spike detection rate of individual electrodes is represented by gray-scale rasters for all 59 electrodes, stacked vertically below each graph. (Each horizontal line pertains to one electrode; gray levels indicate firing rates. The same scale (see color bar next to '4 div') is used for all days. Note that the extreme increase in ASDR during bursts commonly saturates the gray scale. This representation is also used in subsequent figures.) Analogous figures from all 58 cultures used are available online.