From Neural Wiki
 What is a burst leader
In cultured cortical neural networks of mature neurons (20+ days in vitro), the majority of all spike activity (action potentials) occurs in coordinated network wide burst events (see Spontaneous activity) where most of the neurons fire. Interestingly, participating neurons do not begin firing at same time (see figure below). We term the first neuron that fires in the network burst the burst leader. In the figure inset below, neuron 20b is the burst leader.
During the course of many thousands of network bursts over several hours, a statistical view of burst leadership begins to emerge. In the figure below, we observe that neurons do not lead with equal probability (red bars). We find that a majority of network bursts (~84%) are led by a small subgroup of neurons, which we term Major Burst Leaders. Below Major Burst Leaders are neurons with a leadership probability larger than 4% (green line).
 Major Burst Leaders
Over a long enough period of time, all neurons lead at least one network burst. However, a small subgroup of neurons clearly lead at a rate greater than the other neurons. We term these neurons Major Burst Leaders (MBLs). In our paper, we identified these neurons by arbitrarily setting a leadership threshold at 4% of all network bursts, but this could also be done by identifying neurons that lead at 3 times the standard deviation.
We found that the MBL set comprised a small group of neurons, but led a majority of the network bursts. We also found that MBLs were very responsive to one another and that they could respond in a very short amount of time. Therefore we conclude that the MBLs form a highly connected primary circuit which is responsible for initiating the majority of network burst events. This fault tolerant circuit keeps activity flowing in the network.
The paper showing this work was published in the Journal of Computational Neuroscience
Michael I. Ham, Luis M.A. Bettencourt, Floyd D. McDaniel, Guenter W. Gross (2008) Spontaneous coordinated activity in cultured networks: analysis of multiple ignition sites, primary circuits, and burst phase delay distributions. Journal of Computational Neuroscience. 24(3) 346-357