Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA 02118, USA.
Neurobiol Aging. 2012 Oct;33(10):2357-72. doi: 10.1016/j.neurobiolaging.2011.11.015. Epub 2011 Dec 21.
Like humans, rhesus monkeys show cognitive decline and this review considers what structural age-related changes underlie this decline. Some structural measures do not alter significantly with age. These include brain weight, overall cortical thickness; numbers of cortical neurons; and numbers of astrocytes and microglial cells. Other structural measures change with age, but the change does not correlate with cognitive decline. These changes include nerve fiber loss from some fiber tracts, degeneration, and regeneration of myelin sheaths, and increase in the frequency of oligodendrocytes. Among the structural measures that increase in frequency with age and also correlate with cognitive decline are the increased frequency of degenerating myelin sheaths and a loss of nerve fibers from some fiber tracts; and the loss of synapses and dendritic spines from upper layers of prefrontal cortex. Consequently, the existing data suggest that cognitive decline correlates with changes in myelinated nerve fibers and with disconnections between and within cortical areas, as reflected by the age-related loss of synapses and of dendritic spines from some cortical areas.
与人类一样，恒河猴也会出现认知能力下降的情况，而本篇综述考虑了哪些与年龄相关的结构变化是导致这种下降的原因。一些结构测量指标不会随着年龄的增长而显著改变。这些指标包括脑重量、大脑皮质总厚度、皮质神经元数量、星形胶质细胞和小胶质细胞数量。其他结构测量指标会随着年龄的增长而发生变化，但这种变化与认知能力下降没有相关性。这些变化包括一些纤维束的神经纤维损失、髓鞘变性和再生，以及少突胶质细胞的频率增加。在随着年龄增长而频率增加且与认知能力下降相关的结构测量指标中，有髓神经纤维的增加频率以及一些纤维束的神经纤维损失与认知能力下降相关；此外，还包括前额叶皮质上层的突触和树突棘的丢失。因此，现有数据表明，认知能力下降与髓鞘神经纤维的变化以及皮质区域之间和内部的连接中断有关，这反映在一些皮质区域的突触和树突棘随年龄增长而丢失。
