Figure 2.

Reproduction of different spiking patterns in synthetic spike trains. Spike trains were generated by randomly drawing ISI values from a gamma distribution whose shape is controlled by parameter k. A, Regular pattern: k = 500, CoV = 0.05. B, Irregular pattern: k = 1, CoV = 1.0. C, Intermediate regularity: k = 4, CoV = 0.5. Despite an elevated CoV value, this spike train did not reproduce the multimodal ISI histogram or patterned ISI return plot characteristic of semiregular units (compare with Fig. 1C,D). D, The semiregular (integer-multiple) spike pattern was reproduced by randomly removing 30% of spikes from the regular (k = 500) spike train. Removing spikes caused the CoV to increase to 0.53.