Schematic of the computation of Lempel-Ziv complexity LZc.

a) x_i is the activity of the i^th EEG electrode, i.e. the i^th channel, and a_i is the (Hilbert) amplitude of x_i. b) b_i is binarized a_i, using the mean activity of a_i as binarisation threshold. c) After binarisation of all n channels, successive n × 1 dimensional observations are concatenated to obtain one binary sequence s in which patterns are searched and listed into a dictionary of binary words via a Lempel-Ziv algorithm. d) Lempel-Ziv complexity LZc is proportional to the size of this dictionary.