Networks of living neurons exhibit an avalanche mode of activity,
experimentally found in organotypic cultures. Here we present a model based on
self-organized criticality and taking into account brain plasticity, which is
able to reproduce the spectrum of electroencephalograms (EEG). The model
consists in an electrical network with threshold firing and activity-dependent
synapse strenghts. The system exhibits an avalanche activity power law
distributed. The analysis of the power spectra of the electrical signal
reproduces very robustly the power law behaviour with the exponent 0.8,
experimentally measured in EEG spectra. The same value of the exponent is found
on small-world lattices and for leaky neurons, indicating that universality
holds for a wide class of brain models.Comment: 4 pages, 3 figure