MYELIN

在上一个资助期间，我们检查了大脑的几个区域， 年轻人（4至6岁）和老年人（25岁以上）的皮质 恒河猴，并得出结论，没有显着 皮质神经元随年龄增长而丧失。 然而，还有其他 皮质和底层白色区均发生显著变化 所谓了 其中最明显的是在完整性的崩溃， 髓磷脂 这不是脱髓鞘， 她的手还在不停地抚摸着我的鸡巴，那感觉好美妙，好美妙。 最好称之为髓鞘形成障碍。 有证据表明 退化，但这在皮质中并不明显。 此外，委员会认为， 在我们对额叶皮层的研究中，我们发现 髓鞘破坏程度与运动成绩之间的相关性 在延迟不匹配任务上的表现。 在 此外，MCI扫描我们的猴子的大脑半球，显示一个 随着年龄增长，白色物质减少，但灰质不减少。 并且当 将白色物质的损失程度与 猴子的表现，有一个显着的相关性 猴子的表现对收购的组成部分， 延迟不匹配到示例任务。 这些结果使我们 相信髓磷脂完整性的破坏可能是 认知缺陷，因为这将降低传导率沿着 一些轴突和扰乱神经元突触活动的时间 电路. 显然，对老化对髓磷脂影响的深入研究 重要. 我们建议继续进行MCI扫描，以获得更好的数据， 白色物质损失与行为表现之间的相关性。 此外，我们将使用一种新的氚淬灭技术， 确定髓鞘丢失是否在某些皮质区域更普遍， 在另一些情况下，并将结果与记录的 猴子的行为。 最后，我们建议审查的影响， 老化的髓鞘，以确定如何 鞘破裂，什么尺寸的纤维受到的影响最大，以及 髓鞘的分解在整个CNS中同样发生，或 它是否在某些纤维途径中比在其他纤维途径中更突出。 为此，我们选择了检查视觉通路，因为 该系统还提供光纤连接的分层系统， 皮质内和皮质外的联系，其起源和 终端是众所周知的。

During the last grant period we examined several areas of the cerebral cortex of young (4 to 6 years of age) and old (over 25 years of age) rhesus monkeys and came to the conclusion that there is no significant loss of cortical neurons with age. However there are other significant changes both in the cortex and in the underlying white matter. The most obvious of these is a breakdown in the integrity of myelin. This is not demyelination in the sense that the axons are left bare, but a breakdown in the integrity of the sheats that might best be termed ~dysmyelination~. There is some evidence of axonal degeneration, but this is not pronounced in the cortex. Furthermore, in our study of the frontal cortex we found that there is a correlation between the extent of myelin breakdown and the performance of old monkeys on the delayed nonmatching to sample tasks. In addition, MCI scans of the cerebral hemispheres of our monkeys, show a loss of white matter, but not of gray matter, with age. And when the extent of loss of white matter is plotted against the behavioral performance of the monkeys, there is a significant correlation with the performance of the monkeys on the acquisition component of the delayed nonmatching to sample task. These results have lead us to believe that a breakdown in the integrity of myelin might underlie the cognitive deficits, since this would reduce the conduction rates along some axons and disrupt the timing of synaptic activity in neuronal circuits. Obviously, an in depth study of the effect of aging on myelin is important. We propose to continue MCI scans to obtain better data on the correlation between white matter loss and behavioral performance. In addition, we will use a new tritium quenching technique to determine whether myelin loss is more prevalent in some cortical areas that in others, and will correlate the results with the recorded behavior of the monkeys. Finally, we propose to examine the effect of aging on myelin sheaths by electron microscopy, to determine how sheaths break down, what size fibers are most affected, and whether the breakdown of the myelin occurs equally throughout the CNS, or whether it is more prominent in some fiber pathways than in others. For this purpose, we have chosen to examine the visual pathway, since this system offers a hierarchical system of fiber connections, as well as intracortical and extracortical connections, whose origins and terminations are well known.