University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246, Hamburg, Germany.
Department of Health Sciences, Boston University, 635 Commonwealth Avenue, Boston, MA, 02215, USA.
Brain Struct Funct. 2021 May;226(4):979-987. doi: 10.1007/s00429-021-02219-6. Epub 2021 Feb 9.
Structural connections between cortical areas form an intricate network with a high degree of specificity. Many aspects of this complex network organization in the adult mammalian cortex are captured by an architectonic type principle, which relates structural connections to the architectonic differentiation of brain regions. In particular, the laminar patterns of projection origins are a prominent feature of structural connections that varies in a graded manner with the relative architectonic differentiation of connected areas in the adult brain. Here we show that the architectonic type principle is already apparent for the laminar origins of cortico-cortical projections in the immature cortex of the macaque monkey. We find that prenatal and neonatal laminar patterns correlate with cortical architectonic differentiation, and that the relation of laminar patterns to architectonic differences between connected areas is not substantially altered by the complete loss of visual input. Moreover, we find that the degree of change in laminar patterns that projections undergo during development varies in proportion to the relative architectonic differentiation of the connected areas. Hence, it appears that initial biases in laminar projection patterns become progressively strengthened by later developmental processes. These findings suggest that early neurogenetic processes during the formation of the brain are sufficient to establish the characteristic laminar projection patterns. This conclusion is in line with previously suggested mechanistic explanations underlying the emergence of the architectonic type principle and provides further constraints for exploring the fundamental factors that shape structural connectivity in the mammalian brain.
皮质区之间的结构连接形成了一个具有高度特异性的复杂网络。成年哺乳动物皮质中这个复杂网络组织的许多方面都可以通过一个结构类型原则来捕捉，该原则将结构连接与大脑区域的结构分化联系起来。特别是，投射起源的层模式是结构连接的一个突出特征，它以与成年大脑中连接区域的相对结构分化成梯度的方式变化。在这里，我们表明，皮质-皮质投射的层起源的结构类型原则在猕猴未成熟皮质中已经很明显。我们发现，产前和新生儿的层模式与皮质结构分化相关，并且层模式与连接区域之间结构差异的关系在视觉输入完全丧失的情况下并没有实质性改变。此外，我们发现，投射在发育过程中经历的层模式变化的程度与连接区域的相对结构分化成正比。因此，似乎投射的初始层模式偏差通过后来的发育过程逐渐增强。这些发现表明，大脑形成过程中的早期神经发生过程足以建立特征性的层投射模式。这一结论与以前提出的机制解释一致，这些解释是为了阐明结构类型原则的出现，并为探索塑造哺乳动物大脑结构连接的基本因素提供了进一步的限制。
