 
Summary: ScaleFree Brain Functional Networks
Victor M. EguiŽluz,1
Dante R. Chialvo,2
Guillermo A. Cecchi,3
Marwan Baliki,2
and A. Vania Apkarian2
1
Instituto MediterraŽneo de Estudios Avanzados, IMEDEA (CSICUIB), E07122 Palma de Mallorca, Spain
2
Department of Physiology, Northwestern University, Chicago, Illinois, 60611, USA
3
IBM T.J. Watson Research Center, 1101 Kitchawan Rd., Yorktown Heights, New York 10598, USA
(Received 13 January 2004; published 6 January 2005)
Functional magnetic resonance imaging is used to extract 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 versus distance are both scalefree, (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 scalefree smallworld networks, reflect important functional information about
brain states.
