Huttenlocher P R, Dabholkar A S
Department of Pediatrics, Committee on Neurobiology, University of Chicago, Illinois 60637, USA.
J Comp Neurol. 1997 Oct 20;387(2):167-78. doi: 10.1002/(sici)1096-9861(19971020)387:2<167::aid-cne1>3.0.co;2-z.
The formation of synaptic contacts in human cerebral cortex was compared in two cortical regions: auditory cortex (Heschl's gyrus) and prefrontal cortex (middle frontal gyrus). Synapse formation in both cortical regions begins in the fetus, before conceptual age 27 weeks. Synaptic density increases more rapidly in auditory cortex, where the maximum is reached near postnatal age 3 months. Maximum synaptic density in middle frontal gyrus is not reached until after age 15 months. Synaptogenesis occurs concurrently with dendritic and axonal growth and with myelination of the subcortical white matter. A phase of net synapse elimination occurs late in childhood, earlier in auditory cortex, where it has ended by age 12 years, than in prefrontal cortex, where it extends to midadolescence. Synaptogenesis and synapse elimination in humans appear to be heterochronous in different cortical regions and, in that respect, appears to differ from the rhesus monkey, where they are concurrent. In other respects, including overproduction of synaptic contacts in infancy, persistence of high levels of synaptic density to late childhood or adolescence, the absolute values of maximum and adult synaptic density, and layer specific differences, findings in the human resemble those in rhesus monkeys.
对人类大脑皮层两个区域（听觉皮层，即颞横回；前额叶皮层，即额中回）的突触连接形成情况进行了比较。两个皮层区域的突触形成均始于胎儿期，在孕龄27周之前。听觉皮层的突触密度增加更为迅速，在出生后3个月左右达到最大值。额中回的最大突触密度直到15个月龄之后才会达到。突触发生与树突和轴突生长以及皮层下白质的髓鞘形成同时进行。在儿童后期会出现一个净突触消除阶段，在听觉皮层中这个阶段较早结束，12岁时就已结束，而在前额叶皮层中则会持续到青少年中期。人类不同皮层区域的突触发生和突触消除似乎是不同时的，在这方面，似乎与恒河猴不同，恒河猴的突触发生和突触消除是同时进行的。在其他方面，包括婴儿期突触连接的过度产生、高突触密度持续到儿童后期或青少年期、最大和成人突触密度的绝对值以及层特异性差异等，人类的研究结果与恒河猴相似。
