{"title":"Layer 6 corticocortical neurons are a major route for intra- and interhemispheric feedback.","authors":"Simon Weiler, Manuel Teichert, Troy W Margrie","doi":"10.7554/eLife.100478","DOIUrl":null,"url":null,"abstract":"<p><p>The neocortex comprises anatomically discrete yet interconnected areas that are symmetrically located across the two hemispheres. Determining the logic of these macrocircuits is necessary for understanding high level brain function. Here in mice, we have mapped the areal and laminar organization of the ipsi- and contralateral cortical projection onto the primary visual, somatosensory, and motor cortices. We find that although the ipsilateral hemisphere is the primary source of cortical input, there is substantial contralateral symmetry regarding the relative contribution and areal identity of input. Laminar analysis of these input areas show that excitatory Layer 6 corticocortical cells (L6 CCs) are a major projection pathway within and between the two hemispheres. Analysis of the relative contribution of inputs from supra- (feedforward) and infragranular (feedback) layers reveals that contra-hemispheric projections reflect a dominant feedback organization compared to their ipsi-cortical counterpart. The magnitude of the interhemispheric difference in hierarchy was largest for sensory and motor projection areas compared to frontal, medial, or lateral brain areas due to a proportional increase in input from L6 neurons. L6 CCs therefore not only mediate long-range cortical communication but also reflect its inherent feedback organization.</p>","PeriodicalId":11640,"journal":{"name":"eLife","volume":"13 ","pages":""},"PeriodicalIF":6.4000,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11952746/pdf/","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"eLife","FirstCategoryId":"99","ListUrlMain":"https://doi.org/10.7554/eLife.100478","RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"BIOLOGY","Score":null,"Total":0}
引用次数: 0
摘要
新皮层由解剖学上离散但又相互关联的区域组成,这些区域对称地分布在大脑的两个半球。要了解大脑的高级功能,就必须确定这些大电路的逻辑。在小鼠身上,我们绘制了同侧和对侧皮层投射到初级视觉、躯体感觉和运动皮层的区域和层状组织图。我们发现,虽然同侧半球是大脑皮层输入的主要来源,但在输入的相对贡献和区域特征方面,同侧与对侧存在很大的对称性。对这些输入区域的层状分析表明,兴奋性第六层皮质细胞(L6 CCs)是两个半球内部和之间的主要投射途径。对来自皮质上层(前馈)和皮质下层(反馈)的输入的相对贡献分析表明,与皮质同层相比,大脑半球反向投射反映了一种占主导地位的反馈组织。与额叶、内侧或外侧脑区相比,感觉和运动投射区在层次结构上的半球间差异幅度最大,这是因为来自 L6 神经元的输入按比例增加了。因此,L6 CC 不仅介导了大脑皮层的远距离通讯,还反映了其内在的反馈组织。
Layer 6 corticocortical neurons are a major route for intra- and interhemispheric feedback.
The neocortex comprises anatomically discrete yet interconnected areas that are symmetrically located across the two hemispheres. Determining the logic of these macrocircuits is necessary for understanding high level brain function. Here in mice, we have mapped the areal and laminar organization of the ipsi- and contralateral cortical projection onto the primary visual, somatosensory, and motor cortices. We find that although the ipsilateral hemisphere is the primary source of cortical input, there is substantial contralateral symmetry regarding the relative contribution and areal identity of input. Laminar analysis of these input areas show that excitatory Layer 6 corticocortical cells (L6 CCs) are a major projection pathway within and between the two hemispheres. Analysis of the relative contribution of inputs from supra- (feedforward) and infragranular (feedback) layers reveals that contra-hemispheric projections reflect a dominant feedback organization compared to their ipsi-cortical counterpart. The magnitude of the interhemispheric difference in hierarchy was largest for sensory and motor projection areas compared to frontal, medial, or lateral brain areas due to a proportional increase in input from L6 neurons. L6 CCs therefore not only mediate long-range cortical communication but also reflect its inherent feedback organization.
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