Rapp P R, Gallagher M
Center for Behavioral Neuroscience, University at Stony Brook, NY 11794-2575, USA.
Proc Natl Acad Sci U S A. 1996 Sep 3;93(18):9926-30. doi: 10.1073/pnas.93.18.9926.
Hippocampal neuron loss is widely viewed as a hallmark of normal aging. Moreover, neuronal degeneration is thought to contribute directly to age-related deficits in learning and memory supported by the hippocampus. By taking advantage of improved methods for quantifying neuron number, the present study reports evidence challenging these long-standing concepts. The status of hippocampal-dependent spatial learning was evaluated in young and aged Long-Evans rats using the Morris water maze, and the total number of neurons in the principal cell layers of the dentate gyrus and hippocampus was quantified according to the optical fractionator technique. For each of the hippocampal fields, neuron number was preserved in the aged subjects as a group and in aged individuals with documented learning and memory deficits indicative of hippocampal dysfunction. The findings demonstrate that hippocampal neuronal degeneration is not an inevitable consequence of normal aging and that a loss of principal neurons in the hippocampus fails to account for age-related learning and memory impairment. The observed preservation of neuron number represents an essential foundation for identifying the neurobiological effects of hippocampal aging that account for cognitive decline.
海马体神经元的丧失被广泛视为正常衰老的一个标志。此外，神经元退化被认为直接导致了由海马体支持的与年龄相关的学习和记忆缺陷。通过利用改进的神经元数量量化方法，本研究报告了挑战这些长期存在概念的证据。使用莫里斯水迷宫评估了年轻和老年Long-Evans大鼠中依赖海马体的空间学习状态，并根据光学分割技术对齿状回和海马体主细胞层中的神经元总数进行了量化。对于每个海马体区域，作为一个群体的老年受试者以及有记录表明存在指示海马体功能障碍的学习和记忆缺陷的老年个体，其神经元数量均得以保留。这些发现表明，海马体神经元退化并非正常衰老的必然结果，并且海马体中主要神经元的丧失并不能解释与年龄相关的学习和记忆损伤。观察到的神经元数量保留是识别导致认知衰退的海马体衰老神经生物学效应的重要基础。
