Peters A, Sethares C, Moss M B
Department of Anatomy and Neurobiology, Boston University School of Medicine, MA 02118, USA.
Cereb Cortex. 1998 Dec;8(8):671-84. doi: 10.1093/cercor/8.8.671.
The effect of age on layer 1 of area 46 of prefrontal cortex was determined in the cerebral cortices of 15 rhesus monkeys, 13 of which had been behaviorally tested. Five of the monkeys were young (5-7 years of age), three were middle-aged (9-12 years) and seven were old (24-32 years). It was found that with age, layer 1 becomes significantly thinner and the glial limiting membrane becomes thicker. Counts of synapses in layer 1 of seven of these monkeys using the physical disector method on thin sections revealed that compared to young monkeys, there is a 30-60% reduction in the density of synapses per unit volume in old monkeys. This loss of synapses is accompanied by a reduction in the frequency of profiles of postsynaptic dendrites and their spines from the neuropil of layer 1, indicating that some spiny dendrites that belong to the apical dendritic tufts of pyramidal cells are degenerating and being lost with age. Correlation of these morphological changes with the behavioral data shows that there is a significant correlation between the thickness of layer 1 and memory function, as measured by the 2 min delay condition of the delayed non-matching to sample task. Also, there is significant correlation between the numerical density of synapses in layer 1 and three of the behavioral measures used, as well as the Cognitive Impairment Index. Thus, the changes that occur with age in layer 1 provide one possible basis for the age-related cognitive impairment evidenced in monkeys and humans alike.
在15只恒河猴的大脑皮层中确定了年龄对前额叶皮层46区第1层的影响，其中13只进行了行为测试。5只猴子为幼年（5 - 7岁），3只为中年（9 - 12岁），7只为老年（24 - 32岁）。研究发现，随着年龄增长，第1层显著变薄，神经胶质界膜变厚。对其中7只猴子第1层的突触进行计数，采用物理分割法对薄片进行分析，结果显示，与幼年猴子相比，老年猴子每单位体积的突触密度降低了30% - 60%。突触的减少伴随着第1层神经毡中突触后树突及其棘突轮廓频率的降低，这表明一些属于锥体细胞顶端树突簇的有棘树突正在随着年龄增长而退化和丢失。这些形态学变化与行为数据的相关性表明，第1层的厚度与记忆功能之间存在显著相关性，记忆功能通过延迟非匹配样本任务的2分钟延迟条件来衡量。此外，第1层突触的数量密度与所使用的三项行为测量指标以及认知障碍指数之间也存在显著相关性。因此，第1层随年龄发生的变化为猴子和人类中出现的与年龄相关的认知障碍提供了一种可能的基础。
