The activity of cells in the network. The output of different cell types are colour-coded for the sake of clarity; PCs (blue), BCs (red) and MCs (green).

<p>(A,C) Rastergram and average discharge rate of PCs and BCs versus time when inhibition from MCs is turned off. (A) When the network is subjected to a low background noise (0.25 – 0.5 Hz), it started hopping through the stored attractor states. PCs that form a pattern and are active (near) synchronously in different hypercolumns are grouped for visual aid. The x axis represents time, while the y axis represents neuron label. A dot in the rastergram means a spike of a neuron y at time x. (C) The time varying firing rate of all the cells is not evident in the rastergram. Average discharge rate versus time, bin size of 25 ms, makes it clearer. BCs fire at every attractor cycle since they receive excitation from all minicolumns in a hypercolumn. PCs from different patterns, represented by various blue line-strokes, took turns getting active. BCs, keeping step with PCs, had a high firing rate at the beginning of the attractor and tapered off maintaining the excitation - inhibition balance. (B, D) Same as above after the inclusion of MCs inhibition. (D) The late activity of MCs is apparent in the average firing rate. BCs with their characteristic depressing synapses are the first to respond (red). MCs receiving facilitating synapses discharge with a delay (green), and similar to BCs, as mentioned above, are active at every attractor cycle. MCs due to their strong projection to the neighbouring PCs within 100 µm radius (Silberberg & Markram, 2007), shut the activity thereby shifting the excitation - inhibition balance. Thus, presence of MCs inhibition controls the dwell time of the attractor.