Analysis of spontaneous bursting activity in random neural networks

Developing networks can generate bursting activity despite the absence of pacemaker cells and inhibitory synapses. Bursts are generated by positive feedback through excitatory connections and terminated by a slow depression of network excitability. Similar activity has been observed in cultures of spinal neurons containing inhibitory synapses. Is burst generation in these cultures operating according to the mechanism proposed for developing networks? To answer this question without perturbing the activity, we analyzed the burst pattern of individual neurons in active cultures. We observed a correlation between burst size and preceding interburst interval and a rapid rise and progressive decrease in firing rate during a burst. These findings are consistent with the mechanism of burst generation proposed for developing networks.