The regional specification of the cerebral cortex can be described by protomap and protocortex hypotheses. The protomap hypothesis suggests that the regional destiny of cortical neurons and the relative size of the cortical area are genetically determined early during embryonic development. The protocortex hypothesis suggests that the regional growth rate is predominantly shaped by external influences. In order to determine regional volumes of cortical compartments (cortical plate (CP) or subplate (SP)) and estimate their growth rates, we acquired T2-weighted in utero MRIs of 40 healthy fetuses and grouped them into early (<25.5 GW), mid- (25.5–31.6 GW), and late (>31.6 GW) prenatal periods. MRIs were segmented into CP and SP and further parcellated into 22 gyral regions. No significant difference was found between periods in regional volume fractions of the CP or SP. However, during the early and mid-prenatal periods, we found significant differences in relative growth rates (% increase per GW) between regions of cortical compartments. Thus, the relative size of these regions are most likely conserved and determined early during development whereas more subtle growth differences between regions are fine-tuned later, during periods of peak thalamocortical growth. This is in agreement with both the protomap and protocortex hypothesis.

中文翻译：

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胎儿发育过程中区域皮质板和亚板体积生长的时空差异。


大脑皮层的区域规范可以通过原图和原皮层假设来描述。原图假说表明，皮质神经元的区域命运和皮质区域的相对大小是在胚胎发育早期由基因决定的。原皮质假说表明，区域增长率主要受外部影响影响。为了确定皮质区室（皮质板 (CP) 或亚板 (SP)）的区域体积并估计其生长速度，我们获取了 40 个健康胎儿的 T2 加权子宫内 MRI，并将其分为早期 (<25.5 GW) ）、产前中期（25.5–31.6 GW）和产后期（>31.6 GW）。 MRI 分为 CP 和 SP，并进一步分为 22 个脑回区域。不同时期之间 CP 或 SP 的区域体积分数没有发现显着差异。然而，在产前早期和中期，我们发现皮质区室区域之间的相对生长率（每GW的增长百分比）存在显着差异。因此，这些区域的相对大小很可能在发育早期得到保留和确定，而区域之间更微妙的生长差异则在丘脑皮质生长高峰期后期进行微调。这与原图和原皮质假说一致。