How to Direct the Edges of the Connectomes: Dynamics of the Consensus Connectomes and the Development of the Connections in the Human Brain.
How to Direct the Edges of the Connectomes: Dynamics of the Consensus Connectomes and the Development of the Connections in the Human Brain.
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DOI：
10.1371/journal.pone.0158680
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发表时间：
2016
期刊：
影响因子：
3.7
通讯作者：
Grolmusz V
中科院分区：
文献类型：
--
作者：
Kerepesi C;Szalkai B;Varga B;Grolmusz V
人类脑图或连接体是当今深入研究的对象。图论方法在脑科学中的优势在于，图论的丰富结构、算法和定义可以应用于人脑连接的解剖网络。在这些图中，顶点对应于灰质的小区域（1-1.5 cm2），如果基于弥散磁共振成像的工作流程发现轴突纤维，则两个顶点由边缘连接，轴突在大脑白质中的这些小灰质区域之间运行。当今该领域的一个主要问题是发现小灰质区域之间联系的方向。在之前的工作中，我们报道了布达佩斯参考连接组服务器http://connectome.pitgroup.org的构建，该服务器是根据NIH人类连接组项目中记录的数据构建的。服务器根据可选参数生成版本2中96名受试者的共识脑图，版本3中418名受试者的共识脑图。在布达佩斯参考连接体服务器发布之后，我们发现了该服务器的一个令人惊讶且无法预料的特性。对于k = 1,2，…，418的任意值，服务器可以生成至少k个图中存在的连接的脑图。当通过移动web服务器上的滑块从右向左将k的值从k = 418更改为1时，共识图中肯定会出现越来越多的边。令人惊讶的是，新边缘的出现并不是随机的：它类似于生长中的灌木。我们把这种现象称为共识连接体动力学。我们假设，网络服务器中滑块的移动可能复制了人类大脑中连接的发展，在以下意义上：所有受试者中出现的连接都是最古老的连接，而那些只在越来越少的受试者中出现的连接逐渐成为个体大脑发展中较新的连接。关于这一现象的动画可以在https://youtu.be/yxlyudPaVUE上找到。基于这一观察和相关假设，我们可以为连接组的一些边分配如下方向：设Gk +1表示每个边至少出现在k+1个图中的共识连接组，设Gk表示每个边至少出现在k个图中的共识连接组。假设顶点v没有连接到Gk+1中的任何其他顶点，而是连接到Gk中的顶点u，其中u连接到已经在Gk+1中的其他顶点。然后我们把这条（v, u）边从v指向u。
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 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. One main question of the field today is discovering the directions of the connections between the small gray matter areas. In a previous work we have reported the construction of the Budapest Reference Connectome Server http://connectome.pitgroup.org from the data recorded in the Human Connectome Project of the NIH. The server generates the consensus braingraph of 96 subjects in Version 2, and of 418 subjects in Version 3, 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 418, for any value of k = 1, 2, …, 418. When the value of k is changed from k = 418 through 1 by moving a slider at the webserver from right to left, 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 shrub. We refer to this phenomenon as the Consensus Connectome Dynamics. We hypothesize that this movement of the slider in the webserver may copy the development of the connections in the human brain in the following sense: the connections that are present in all subjects are the oldest ones, and those that are present only in a decreasing fraction of the subjects are gradually the newer connections in the individual brain development. An animation on the phenomenon is available at https://youtu.be/yxlyudPaVUE. Based on this observation and the related hypothesis, we can assign directions to some of the edges of the connectome as follows: Let Gk + 1 denote the consensus connectome where each edge is present in at least k+1 graphs, and let Gk denote the consensus connectome where each edge is present in at least k graphs. Suppose that vertex v is not connected to any other vertices in Gk+1, and becomes connected to a vertex u in Gk, where u was connected to other vertices already in Gk+1. Then we direct this (v, u) edge from v to u.