File:An animation of the edges of the Budapest Reference Connectome Server.webm

English: The human braingraph or the connectome is the object of an intensive research today. The advantage of the graph-approach to brain science is that the rich structures, algorithms and definitions of graph theory can be applied to the 1000-node anatomical networks of the connections of the human brain. In these graphs, the vertices correspond to the small (1-1.5 cm²) areas of the gray matter, and two vertices are connected by an edge, if a diffusion-MRI based workflow finds fibers of axons, running between those small gray matter areas in the white matter of the brain. In a previous work we have reported the construction of the Budapest Reference Connectome Server http://connectome.pitgroup.org, which generates the consensus braingraph of 96 subjects, according to selectable parameters. After the Budapest Reference Connectome Server had been published, we recognized a surprising and unforeseen property of the server. The server can generate the braingraph of connections that are present in at least k graphs out of the 96, for any value of k=1,2,...,96. When the value of k is changed from k=96 through 1 by moving a slider at the webserver, certainly more and more edges appear in the consensus graph. The astonishing observation is that the appearance of the new edges is not random: it is similar to a growing tree. The animation enclosed is the work of Balint Varga. Further information: https://arxiv.org/abs/1509.05703