Department of Neurology and Clinical Neuroscience, Faculty of Medicine, University of Freiburg, Breisacher Str. 64, 79106 Freiburg, Germany.
Department of Medical Physics, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
Neuroimage. 2021 Jul 1;234:117977. doi: 10.1016/j.neuroimage.2021.117977. Epub 2021 Mar 21.
The brain hemispheres can be divided into an upper dorsal and a lower ventral system. Each system consists of distinct cortical regions connected via long association tracts. The tracts cross the central sulcus or the limen insulae to connect the frontal lobe with the posterior brain. The dorsal stream is associated with sensorimotor mapping. The ventral stream serves structural analysis and semantics in different domains, as visual, acoustic or space processing. How does the prefrontal cortex, regarded as the platform for the highest level of integration, incorporate information from these different domains? In the current view, the ventral pathway consists of several separate tracts, related to different modalities. Originally the assumption was that the ventral path is a continuum, covering all modalities. The latter would imply a very different anatomical basis for cognitive and clinical models of processing. To further define the ventral connections, we used cutting-edge in vivo global tractography on high-resolution diffusion tensor imaging (DTI) data from 100 normal subjects from the human connectome project and ex vivo preparation of fiber bundles in the extreme capsule of 8 humans using the Klingler technique. Our data showed that ventral stream tracts, traversing through the extreme capsule, form a continuous band of fibers that fan out anteriorly to the prefrontal cortex, and posteriorly to temporal, occipital and parietal cortical regions. Introduction of additional volumes of interest in temporal and occipital lobes differentiated between the inferior fronto-occipital fascicle (IFOF) and uncinate fascicle (UF). Unequivocally, in both experiments, in all subjects a connection between the inferior frontal and middle-to-posterior temporal cortical region, otherwise known as the temporo-frontal extreme capsule fascicle (ECF) from nonhuman primate brain-tracing experiments was identified. In the human brain, this tract connects the language domains of "Broca's area" and "Wernicke's area". The differentiation in the three tracts, IFOF, UF and ECF seems arbitrary, all three pass through the extreme capsule. Our data show that the ventral pathway represents a continuum. The three tracts merge seamlessly and streamlines showed considerable overlap in their anterior and posterior course. Terminal maps identified prefrontal cortex in the frontal lobe and association cortex in temporal, occipital and parietal lobes as streamline endings. This anatomical substrate potentially facilitates the prefrontal cortex to integrate information across different domains and modalities.
大脑半球可以分为上背侧和下腹侧系统。每个系统都由通过长的联合束连接的不同皮质区域组成。这些束穿过中央沟或岛阈连接额叶与脑后部。背侧流与感觉运动映射相关。腹侧流在不同领域（如视觉、听觉或空间处理）中提供结构分析和语义。作为最高水平整合的平台，前额叶皮层如何整合来自这些不同领域的信息？在当前的观点中，腹侧通路由与不同模式相关的几个单独的束组成。最初的假设是，腹侧路径是一个连续体，涵盖了所有模式。后者将意味着认知和临床处理模型的解剖基础非常不同。为了进一步定义腹侧连接，我们使用来自人类连接组计划的 100 名正常受试者的高分辨率弥散张量成像（DTI）数据的最先进的活体全局束追踪技术，以及使用 Klingler 技术对 8 名人类的极胶囊中的纤维束进行的离体准备。我们的数据表明，穿过极胶囊的腹侧流束形成了一个连续的纤维带，向前部扩展到前额叶皮层，向后部扩展到颞叶、枕叶和顶叶皮质区域。在颞叶和枕叶中引入额外的感兴趣区域，可区分下额枕束（IFOF）和钩束（UF）。在这两个实验中，在所有受试者中，在所有受试者中，都可以识别出非人类灵长类动物脑追踪实验中已知的额下回和中后颞皮质区域之间的连接，即来自非人类灵长类动物脑追踪实验的颞额极胶囊束（ECF）。在人类大脑中，这条束连接语言领域的“布罗卡区”和“韦尼克区”。IFOF、UF 和 ECF 这三个束的分化似乎是任意的，它们都穿过极胶囊。我们的数据表明，腹侧通路代表一个连续体。这三个束无缝融合，流线在其前部和后部的路径上显示出相当大的重叠。末端图谱确定了额叶中的前额叶皮层和颞叶、枕叶和顶叶中的联合皮层作为流线的终点。这种解剖学基础有可能促进前额叶皮层整合来自不同领域和模式的信息。
