Small-world properties of human brain functional networks based on resting-state functional MRI

Studying the resting state functional activities of healthy human brain will aid us to understand the patterns of functional activities of human brain in normal or disease states. Time series of 90 brain regions were extracted from resting state functional magnetic resonance imagines in 19 healthy volunteers. Functional correlations between brain regions were calculated, and the thresholds were set to establish the simple undirected graphs, then some measurements of brain functional networks were computed, finally the degree distribution was fitted. The results confirmed that the human brain functional networks have both big clustering coefficients like regular networks and small characteristic path lengths similar like random networks, degree distribution met exponentially truncated power-law distribution. Taken together, the brain functional networks have small world properties.