Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Cidade Universitária Rio de Janeiro, Brasil ; Instituto Nacional de Neurociência Translacional, MCT/CNPq São Paulo, Brasil.
Front Neuroanat. 2013 Sep 2;7:28. doi: 10.3389/fnana.2013.00028. eCollection 2013.
The human prefrontal cortex has been considered different in several aspects and relatively enlarged compared to the rest of the cortical areas. Here we determine whether the white and gray matter of the prefrontal portion of the human cerebral cortex have similar or different cellular compositions relative to the rest of the cortical regions by applying the Isotropic Fractionator to analyze the distribution of neurons along the entire anteroposterior axis of the cortex, and its relationship with the degree of gyrification, number of neurons under the cortical surface, and other parameters. The prefrontal region shares with the remainder of the cerebral cortex (except for occipital cortex) the same relationship between cortical volume and number of neurons. In contrast, both occipital and prefrontal areas vary from other cortical areas in their connectivity through the white matter, with a systematic reduction of cortical connectivity through the white matter and an increase of the mean axon caliber along the anteroposterior axis. These two parameters explain local differences in the distribution of neurons underneath the cortical surface. We also show that local variations in cortical folding are neither a function of local numbers of neurons nor of cortical thickness, but correlate with properties of the white matter, and are best explained by the folding of the white matter surface. Our results suggest that the human cerebral cortex is divided in two zones (occipital and non-occipital) that differ in how neurons are distributed across their gray matter volume and in three zones (prefrontal, occipital, and non-occipital) that differ in how neurons are connected through the white matter. Thus, the human prefrontal cortex has the largest fraction of neuronal connectivity through the white matter and the smallest average axonal caliber in the white matter within the cortex, although its neuronal composition fits the pattern found for other, non-occipital areas.
人类前额叶皮层在几个方面被认为与皮质的其他区域不同，并且相对较大。在这里，我们通过应用各向同性分数器来分析神经元在皮质整个前后轴上的分布及其与脑回程度、皮质表面下神经元数量和其他参数的关系，来确定人类大脑前额叶皮质的白质和灰质与皮质的其余部分是否具有相似或不同的细胞组成。前额叶区域与大脑皮质的其余部分（除了枕叶皮质外）共享相同的皮质体积和神经元数量之间的关系。相比之下，枕叶和前额叶区域通过白质与其他皮质区域的连接方式不同，白质中的皮质连接系统减少，沿前后轴的平均轴突口径增加。这两个参数解释了皮质表面下神经元分布的局部差异。我们还表明，皮质折叠的局部变化既不是局部神经元数量的函数，也不是皮质厚度的函数，而是与白质的特性相关，并且与白质表面的折叠最相关。我们的研究结果表明，人类大脑皮质可以分为两个区（枕叶和非枕叶），这两个区在神经元在灰质体积中的分布方式上存在差异，以及三个区（前额叶、枕叶和非枕叶）在神经元通过白质连接的方式上存在差异。因此，尽管人类前额叶皮层的神经元组成符合其他非枕叶区域的模式，但它的白质中神经元连接的比例最大，白质中的平均轴突口径最小。
