Leuba G, Garey L J
Hum Neurobiol. 1987;6(1):11-8.
Neuronal numerical density in area 17 of the human cerebral cortex was estimated over a wide range of ages from mid-gestation to old age. The density at 21 weeks of gestation is very high (over one million/mm3) and decreases steeply but regularly until birth, when it is around 90,000 neurons/mm3. It continues to decrease until about 4 months postnatally, when it reaches values of about 40,000 neurons/mm3. Thereafter neuronal density remains more or less stable and the mean value for young adults is about 35,000 neurons/mm3. Values for supragranular, granular and infragranular layers follow a similar temporal sequence and also stabilize a few months postnatally. However, until 31 weeks of gestation, the granular layer IVc has a slightly lower neuronal density than that of the supragranular zone including layers II, III, IVa and b. Around birth, the neuronal density of layer IVc is about double that in supragranular layers and remains relatively high in the adult. With aging the cortical neuronal density again increases slightly, reaching a mean of 44,000 neurons/mm3 for five cases aged over 80 years. The number of neurons under one square millimeter of cerebral cortex also undergoes a very steep decrease until birth, stabilizes a few months after birth and seems to remain stable in adult and old age. We find no conclusive evidence for neuronal loss with aging.
在从妊娠中期到老年的广泛年龄段范围内，对人类大脑皮质17区的神经元数量密度进行了估计。妊娠21周时密度非常高（超过100万/mm³），并在出生前急剧但有规律地下降，出生时约为90,000个神经元/mm³。它继续下降，直到出生后约4个月，此时达到约40,000个神经元/mm³的值。此后神经元密度或多或少保持稳定，年轻成年人的平均值约为35,000个神经元/mm³。颗粒上层、颗粒层和颗粒下层的值遵循类似的时间序列，并且在出生后几个月也趋于稳定。然而，直到妊娠31周，颗粒层IVc的神经元密度略低于包括II、III、IVa和b层在内的颗粒上层区域。出生时，IVc层的神经元密度约为颗粒上层的两倍，并且在成年人中仍然相对较高。随着年龄增长，皮质神经元密度再次略有增加，80岁以上的5例病例平均达到44,000个神经元/mm³。每平方毫米大脑皮质下的神经元数量在出生前也经历非常急剧的下降，在出生后几个月稳定下来，并且在成年和老年似乎保持稳定。我们没有发现关于衰老导致神经元丢失的确凿证据。
