Neuron number in the parahippocampal region is preserved in aged rats with spatial learning deficits
Neuron number in the parahippocampal region is preserved in aged rats with spatial learning deficits
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DOI：
10.1093/cercor/12.11.1171
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发表时间：
2002-11-01
期刊：
影响因子：
3.7
通讯作者：
Burwell, RD
中科院分区：
文献类型：
--
作者：
Rapp, PR;Deroche, PS;Burwell, RD
内嗅、嗅周和海马旁皮质在解剖学上定位为介导海马和新皮质之间的双向信息流。与这种组织相一致，海马旁区的损伤会导致年轻受试者的学习和记忆障碍。虽然最近的证据表明，海马中的神经元死亡是不需要解释正常老化对学习和记忆的影响，其他研究结果表明，海马旁与海马的相互作用的变化可能发挥重要作用。在这种背景下，我们测试了海马学习中与年龄相关的缺陷与海马旁区域神经元死亡相关联的可能性。该实验利用了一个良好表征的认知老化大鼠模型，结合体视学方法定量神经元数量。结果表明，在正常老化过程中，内嗅、嗅周和嗅后皮质中的神经元总数在很大程度上得以保留。此外，老年大鼠海马学习的个体差异与任何区域的神经元数量均不相关，并且没有迹象表明老年动物中最明显的认知障碍有选择性或不成比例的损失。与来自同一研究人群的早期发现一起，结果表明，在海马系统的任何主要的细胞结构定义的组成部分中，在没有显著神经元死亡的情况下，可以发生与年龄相关的认知能力下降。这些发现为确定认知老化的基础提供了一个基本框架，表明连接和其他变化的改变更可能是致病因素。
The entorhinal, perirhinal and parahippocampal cortices are anatomically positioned to mediate the bi-directional flow of information between the hippocampus and neocortex. Consistent with this organization, damage involving the parahippocampal region causes significant learning and memory impairment in young subjects. Although recent evidence indicates that neuron death in the hippocampus is not required to account for the effects of normal aging on learning and memory, other findings suggest that changes in parahippocampal interactions with the hippocampus may play significant role. Prompted by this background, we tested the possibility that age-related deficits in hippocampal learning are coupled with neuron death in the parahippocampal region. The experiments took advantage of a well-characterized rat model of cognitive aging in combination with stereological methods for quantifying neuron number. The results demonstrate that total neuron number in the entorhinal, perirhinal and postrhinal cortices is largely preserved during normal aging. Furthermore, individual variability in hippocampal learning among the aged rats failed to correlate with neuron number in any region examined and there was no indication of selective or disproportionate loss among the aged animals with the most pronounced cognitive impairment. Taken together with earlier findings from the same study population, the results demonstrate that age-related cognitive decline can occur in the absence of significant neuron death in any major, cytoarchitectonically defined component of the hippocampal system. These findings provide an essential framework for identifying the basis of cognitive aging, suggesting that alterations in connectivity and other changes are more likely causative factors.