一项研究说，大脑回路可能是以一种类似于互联网的互相连接的反馈网络方式组织起来。科学家长久以来认为大脑是一种自上而下的等级，最晚进化出来部分（诸如新皮层）处于命令链的顶端。但是近来的报告提示了一个反馈网络回路。为了研究大脑回路的结构，Richard H. Thompson 和Larry W. Swanson对称为背内侧伏核的大鼠脑区域的1立方毫米应用了一种实验性的回路追踪技术。该区域因为其被认为在奖赏和渴求的过程中起作用而称为“快乐的热区”。这组作者发现，在这个被认为控制着食欲、压力和抑郁的区域内广为分布的灰质群之间存在一系列的互联连接。这组作者报告说，这些连接形成了一系列纵向的回路。此外，该区域是包括了皮层、基底神经节、丘脑和下丘脑在内的前脑的一个大反馈回路的一部分；对该区域的神经输入和输出进行测绘提示了反馈网络而非等级结构的特征。这组作者说，这些发现意味着这种追踪技术可能用于构建整个神经系统的一个连线图。（生物谷Bioon.com）
生物谷推荐原文出处：
PNAS doi: 10.1073/pnas.1009112107
Hypothesis-driven structural connectivity analysis supports network over hierarchical model of brain architecture
Richard H. Thompson and Larry W. Swanson1
Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089
The brain is usually described as hierarchically organized, although an alternative network model has been proposed. To help distinguish between these two fundamentally different structure-function hypotheses, we developed an experimental circuit-tracing strategy that can be applied to any starting point in the nervous system and then systematically expanded, and applied it to a previously obscure dorsomedial corner of the nucleus accumbens identified functionally as a “hedonic hot spot.” A highly topographically organized set of connections involving expected and unexpected gray matter regions was identified that prominently features regions associated with appetite, stress, and clinical depression. These connections are arranged as a longitudinal series of circuits (closed loops). Thus, the results do not support a rigidly hierarchical model of nervous system organization but instead indicate a network model of organization. In principle, the double-coinjection circuit tracing strategy can be applied systematically to the rest of the nervous system to establish the architecture of the global structural wiring diagram, and its abstraction, the connectome.
