  Functional magnetic resonance imaging (fMRI) is used to extract {\em
functional networks} connecting correlated human brain sites. Analysis of the
resulting networks in different tasks shows that: (a) the distribution of
functional connections, and the probability of finding a link vs. distance are
both scale-free, (b) the characteristic path length is small and comparable
with those of equivalent random networks, and (c) the clustering coefficient is
orders of magnitude larger than those of equivalent random networks. All these
properties, typical of scale-free small world networks, reflect important
functional information about brain states.
