Functional Architecture of Memory Unit, Mercator Research Group, Faculty of Medicine, Ruhr University Bochum, Bochum, Germany.
J Neurosci. 2013 Jul 10;33(28):11506-14. doi: 10.1523/JNEUROSCI.4480-12.2013.
A prevailing view in memory research is that CA3 principally supports spatial processes. However, few studies have investigated the contribution of CA3 to nonspatial memory function. Interestingly, the proximal part of CA3 (close to the dentate gyrus) predominantly projects to distal CA1 (away from the dentate gyrus), which preferentially processes nonspatial information. Moreover, the cytoarchitecture and connectivity patterns in the proximal and distal parts of CA3 strongly differ, suggesting a functional segregation in this area. Here, we tested whether CA3 is recruited during nonspatial recognition memory, and whether nonspatial information is differentially represented along the proximodistal axis of CA3. Furthermore, we investigated whether the pattern of activation within CA3 would mirror that of CA1. We used a high-resolution imaging technique specifically designed to analyze brain activity in distant areas that is based on the detection of the expression of the immediate-early gene Arc, used as a marker of neuronal activation. We showed that proximal CA3 is strongly recruited during a nonspatial delayed nonmatching-to-sample recognition memory task in rats, while distal CA3 is not. In addition, distal CA1 was more activated than proximal CA1 in the same task. These findings suggest a functional segregation of CA3 that mirrors that of CA1, and potentially indicate the existence of a proximal CA3-distal CA1 hippocampal subnetwork that would preferentially process nonspatial information during recognition memory.
在记忆研究中,一种流行的观点认为 CA3 主要支持空间过程。然而,很少有研究调查 CA3 对非空间记忆功能的贡献。有趣的是,CA3 的近端部分(靠近齿状回)主要投射到远端 CA1(远离齿状回),后者优先处理非空间信息。此外,CA3 的近端和远端部分的细胞结构和连接模式差异很大,表明该区域存在功能分离。在这里,我们测试了 CA3 是否在非空间识别记忆中被招募,以及非空间信息是否沿着 CA3 的近-远轴被不同地表示。此外,我们还研究了 CA3 内的激活模式是否会反映 CA1 的模式。我们使用了一种专门设计的高分辨率成像技术来分析基于即时早期基因 Arc 表达检测的远距离脑区的活动,Arc 被用作神经元激活的标志物。我们发现,在大鼠的非空间延迟非匹配样本识别记忆任务中,CA3 的近端部分被强烈招募,而 CA3 的远端部分则没有。此外,在相同的任务中,CA1 的远端比 CA1 的近端更活跃。这些发现表明 CA3 的功能分离与 CA1 相似,并可能表明存在一个近端 CA3-远端 CA1 海马亚网络,在识别记忆期间优先处理非空间信息。