The corpus callosum is the largest white matter pathway connecting homologous structures of the two cerebral hemispheres. Remarkably, children and adults with developmental absence of the corpus callosum (callosal dysgenesis, CD) show typical interhemispheric integration, which is classically impaired in adult split-brain patients, for whom the corpus callosum is surgically severed. Tovar-Moll and colleagues (2014) proposed alternative neural pathways involved in the preservation of interhemispheric transfer. In a sample of six adults with CD, they revealed two homotopic bundles crossing the midline via the anterior and posterior commissures and connecting parietal cortices, and the microstructural properties of these aberrant bundles were associated with functional connectivity of these regions. The aberrant bundles were specific to CD and not visualised in healthy brains. We extended this study in a developmental cohort of 20 children with CD and 29 typically developing controls (TDC). The two anomalous white-matter bundles were visualised using tractography. Associations between structural properties of these bundles and their regional functional connectivity were explored. The proposed atypical bundles were observed in 30% of our CD cohort crossing via the anterior commissure, and in 30% crossing via the posterior commissure (also observed in 6.9% of TDC). However, the structural property measures of these bundles were not associated with parietal functional connectivity, bringing into question their role and implication for interhemispheric functional connectivity in CD. It is possible that very early disruption of embryological callosal development enhances neuroplasticity and facilitates the formation of these proposed alternative neural pathways, but further evidence is needed.

中文翻译：

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重新审视出生时没有胼胝体的儿童的大脑重新布线和可塑性

胼胝体是连接两个大脑半球同源结构的最大白质通路。值得注意的是，胼胝体发育缺失（胼胝体发育不全，CD）的儿童和成人表现出典型的大脑半球间整合，这在成人裂脑患者中典型地受损，他们的胼胝体被手术切断。Tovar-Moll 及其同事 (2014) 提出了参与保存半球间转移的替代神经通路。在六名患有 CD 的成年人的样本中，他们发现两个同伦束通过前后连合穿过中线并连接顶叶皮质，并且这些异常束的微观结构特性与这些区域的功能连接性相关。异常束是 CD 特有的，在健康的大脑中不可见。我们在 20 名 CD 儿童和 29 名典型发育对照 (TDC) 的发育队列中扩展了这项研究。两个异常白质束通过纤维束显像术进行了可视化。探讨了这些束的结构特性与其区域功能连接性之间的关联。在我们的 CD 队列中，30% 的人通过前连合观察到提出的非典型束，30% 的人通过后连合（在 TDC 的 6.9% 中也观察到）。然而，这些束的结构特性测量与顶叶功能连通性无关，从而质疑它们在 CD 中的作用和对大脑半球间功能连通性的影响。