Figure 1

An example of a raster plot presentation of the recorded network activity showing the synchronized bursting events and a closer look at an individual event (top two boxes). The binary vector of an individual event is shown in the third box and its corresponding activity density $D_j^n(t)$ is shown in the bottom box. A SBE is identified whenever the number of neurons that fired during a time segment of 100 ms exceeds a threshold (usually taken to be 80% of the total number of recorded neurons).Reuse & Permissions

Figure 2

(a) An example of the inter-SBE correlation matrix $EC(n,m)$ for a sequence of 300 SBEs. The gray levels represent the degrees of correlations using the standard TV scale. (b) A segment of the recorded sequence of the SBEs and their relative distances $ED(n,m)$ represented as the connecting heights. (c) The reordered correlation matrix. Note that this reordered sequence does form a clear block organization hinting about the existence of distinct subgroups of SBEs. (d) A segment of the recorded sequence of SBEs sorted according to the subgroups shown in (c) to demonstrate that they are mixed in their order of temporal appearances.Reuse & Permissions

Figure 3

The correlation matrix for a recorded sequence of SBEs in the presence of different levels of calcium: events No. 1–50, 51–100, and 101–150 correspond to 0.5, 2, and 1 mM extracellular ${\mathrm{Ca}}^{++}$, respectively.Reuse & Permissions

Figure 4

The interneuron correlations for the two larger subgroups of SBEs (the larger blocks) shown in Fig. 2c. On the left we show the dendrogram correlation circle, and on the right the corresponding connectivity networks in the physical space. The links represent the correlations $NC(i,j)$ (using gray levels) above a 0.7 threshold. In this figure the number of each neuron is the number of the electrode through which it is recorded.Reuse & Permissions

Figure 5

(a),(c) A raster representation of 20 SBEs simultaneously drawn from the largest subgroups of SBEs (a) and the second largest block (b) (both represented in Fig. 2). Each subgroup of 20 rows represents the firing of a single neuron. The times of the spikes are measured with respect to the SBE time. The neurons fire with a high degree of repetition between successive SBEs. (b),(d). An evaluation of the probability to fire of each neuron during the SBEs from the two larger subgroups. This representation enables one to evaluate the correspondence between the division into subgroups. Note that each neuron has its own delay with respect to the other neurons. For example, the activity of the 6th neuron, which during SBEs from subgroup 1 exhibits three spikes and during subgroup 3 exhibits only one spike.Reuse & Permissions