目的:认为Geniculocalcarine纤维仅同侧。然而,最近的发现挑战了这种信念,揭示了在单侧刺激人类外侧膝状核(LGN)时,枕部-颞顶叶区域的双侧募集反应。这增加了对主要视觉区域(V1)的双侧投影的有趣可能性。这项研究试图探索假想的野猪道的倒流。
方法:检查了来自HumanConnectome项目的40位健康个体的7TMR图像。采用MRtrix3软件与约束球面反褶积算法,扫描已处理。LGN作为种子区,和对侧感兴趣区域-ROI(call体-SCC,后连合,LGN,V1,pulvinar,和上丘)被定义为重建假设的截流纤维。在所有分割中都包括对侧V1作为目标区域,排除同侧V1以消除通向或源自该区域的纤维。此外,对源自LGN并投射到同侧V1的束进行了分割。从密度图中提取平均分数各向异性和平均扩散率度量。
结果:观察显示,LGN和对侧V1之间有大量的纤维通过SCC,虽然比同侧纤维小得多。两侧同侧纤维的体积相似。源自左LGN的截流纤维是源自右LGN的纤维的两倍以上。与其他ROI的分割没有产生纤维。
结论:这项研究表明,LGN和V1之间的纤维部分收缩,可能构成了天南药道。
BACKGROUND: Geniculocalcarine fibers are thought to be exclusively ipsilateral. However, recent findings challenged this belief, revealing bilateral recruiting responses in occipitotemporoparietal regions upon unilateral stimulation of the lateral geniculate nucleus (LGN) in humans. This raised the intriguing possibility of bilateral projections to primary visual areas (V1). This study sought to explore the hypothetical decussation of the geniculocalcarine tract.
METHODS: 40 healthy individuals\' 7T magnetic resonance images from the Human Connectome Project were examined. Employing MRtrix3 software with the constrained spherical deconvolution algorithm, scans were processed. LGN served as the seed region and contralateral regions of interest (splenium of the corpus callosum, posterior commissure, LGN, V1, pulvinar, and superior colliculus) were defined to reconstruct the hypothetical decussated fibers. Tractography included contralateral V1 as the target region in all segmentations, excluding ipsilateral V1 to eliminate fibers leading to or originating from this area. Additionally, a segmentation of the tract originating from LGN and projecting to the ipsilateral V1 was performed. Mean fraction anisotropy and mean diffusivity metrics were extracted from the density maps.
RESULTS: Observations revealed a substantial volume of decussated fibers between LGN and contralateral V1 via the splenium of the corpus callosum, albeit much smaller than ipsilateral fibers. The volume of ipsilateral fibers was similar in both sides. Left LGN-originating decussated fibers were more than double those originating from the right LGN. Tract segmentation to other regions of interests yielded no fibers.
CONCLUSIONS: This study suggests a partial decussation of the fibers between LGN and V1, likely constituting the geniculocalcarine tract.