HIPPOCAMPAL CONJUNCTIVE ENCODING, STORAGE, AND RECALL - AVOIDING A TRADE-OFF
HIPPOCAMPAL CONJUNCTIVE ENCODING, STORAGE, AND RECALL - AVOIDING A TRADE-OFF
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DOI：
10.1002/hipo.450040605
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发表时间：
1994-12-01
期刊：
影响因子：
3.5
通讯作者：
MCCLELLAND, JL
中科院分区：
文献类型：
--
作者：
OREILLY, RC;MCCLELLAND, JL
海马体和相关结构被认为能够：1）以最小化分配给不同皮层模式的表征的重叠的方式来表示皮层活动（模式分离）; 2）修改突触连接，使得这些表征稍后可以从存储时存在的皮层活动模式的部分或噪声版本中恢复（模式完成）。我们指出，模式分离和完成之间有一个权衡，并提出海马体独特的解剖和生理特性可能有助于最大限度地减少这种权衡。我们使用分析方法来确定定量估计的分离和完成指定的参数化模型的海马。然后，这些估计被用来评估各种属性和海马的作用，如在不同海马区域看到的活动水平，突触增强和抑郁，系统的多层连接，以及相对集中和强大的凌乱的纤维投射。本分析集中于从内嗅皮层（EC）到齿状回（DG）和CA 3区的前馈通路。我们的研究结果如下：1）Hebbian突触修饰（LTP）促进完成，但减少分离，除非从非活动的突触前单位到活动的突触后单位的突触强度降低（LTD）。2)多层，如在EC到DG到CA 3中，允许图案分离的复合，但不允许图案完成。3)杂乱纤维所携带的输入信号的变化对分离很重要，而不是原始强度，这可以解释为什么杂乱纤维的输入很少且相对较强，而不是像其他海马通路那样很多且相对较弱。4)EC项目CA 3直接和间接通过DG，这表明，两阶段的途径可能占主导地位，在模式分离和一阶段的途径可能占主导地位，在完成过程中，海马可能使用的方法来增强这种效果进行了讨论。(C)1994 Wiley-Liss，Inc.
The hippocampus and related structures are thought to be capable of 1) representing cortical activity in a way that minimizes overlap of the representations assigned to different cortical patterns (pattern separation); and 2) modifying synaptic connections so that these representations can later be reinstated from partial or noisy versions of the cortical activity pattern that was present at the time of storage (pattern completion). We point out that there is a trade-off between pattern separation and completion and propose that the unique anatomical and physiological properties of the hippocampus might serve to minimize this trade-off. We use analytical methods to determine quantitative estimates of both separation and completion for specified parameterized models of the hippocampus. These estimates are then used to evaluate the role of various properties and of the hippocampus, such as the activity levels seen in different hippocampal regions, synaptic potentiation and depression, the multi-layer connectivity of the system, and the relatively focused and strong messy fiber projections. This analysis is focused on the feedforward pathways from the entorhinal cortex (EC) to the dentate gyrus (DG) and region CA3. Among our results are the following: 1) Hebbian synaptic modification (LTP) facilitates completion but reduces separation, unless the strengths of synapses from inactive presynaptic units to active postsynaptic units are reduced (LTD). 2) Multiple layers, as in EC to DG to CA3, allow the compounding of pattern separation, but not pattern completion. 3) The variance of the input signal carried by the messy fibers is important for separation, not the raw strength, which may explain why the messy fiber inputs are few and relatively strong, rather than many and relatively weak like the other hippocampal pathways. 4) The EC projects to CA3 both directly and indirectly via the DG, which suggests that the two-stage pathway may dominate during pattern separation and the one-stage pathway may dominate during completion; methods the hippocampus may use to enhance this effect are discussed. (C) 1994 Wiley-Liss, Inc.