McClelland J L, Goddard N H
Department of Psychology, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA.
Hippocampus. 1996;6(6):654-65. doi: 10.1002/(SICI)1098-1063(1996)6:6<654::AID-HIPO8>3.0.CO;2-G.
We discuss a framework for the organization of learning systems in the mammalian brain, in which the hippocampus and related areas form a memory system complementary to learning mechanisms in neocortex and other areas. The hippocampal system stores new episodes and "replays" them to the neocortical system, interleaved with ongoing experience, allowing generalization as cortical memories form. The data to account for include: 1) neurophysiological findings concerning representations in hippocampal areas, 2) behavioral evidence demonstrating a spatial role for hippocampus, 3) and effects of surgical and pharmacological manipulations on neuronal firing in hippocampal regions in behaving animals. We hypothesize that the hippocampal memory system consists of three major modules: 1) an invertible encoder subsystem supported by the pathways between neocortex and entorhinal cortex, which provides a stable, compressed, invertible encoding in entorhinal cortex (EC) of cortical activity patterns, 2) a memory separation, storage, and retrieval subsystem, supported by pathways between EC, dentate gyrus and area CA3, including the CA3 recurrent collaterals, which facilitates encoding and storage in CA3 of individual EC patterns, and retrieval of those CA3 encodings, in a manner that minimizes interference, and 3) a memory decoding subsystem, supported by the Shaffer collaterals from area CA1 to area CA3 and the bi-directional pathways between EC and CA3, which provides the means by which a retrieved CA3 coding of an EC pattern can reinstate that pattern on EC. This model has shown that 1) there is a trade-off between the need for information-preserving, structure-extracting encoding of cortical traces and the need for effective storage and recall of arbitrary traces, 2) long-term depression of synaptic strength in the pathways subject to long-term potentiation is crucial in preserving information, 3) area CA1 must be able to exploit correlations in EC patterns in the direct perforant path synapses.
我们讨论了哺乳动物大脑中学习系统的组织框架，其中海马体及相关区域构成了一个与新皮层和其他区域的学习机制互补的记忆系统。海马体系统存储新的事件并将它们“重放”到新皮层系统，与正在进行的体验交织在一起，从而在皮层记忆形成时实现泛化。需要解释的数据包括：1）关于海马体区域表征的神经生理学发现，2）证明海马体具有空间作用的行为证据，3）手术和药物操作对行为动物海马体区域神经元放电的影响。我们假设海马体记忆系统由三个主要模块组成：1）一个由新皮层和内嗅皮层之间的通路支持的可逆编码器子系统，它在内嗅皮层（EC）中为皮层活动模式提供稳定、压缩、可逆的编码；2）一个由EC、齿状回和CA3区之间的通路支持的记忆分离、存储和检索子系统，包括CA3区的递归侧支，它有助于在CA3区对单个EC模式进行编码和存储，并以最小化干扰的方式检索这些CA3编码；3）一个由从CA1区到CA3区的谢弗侧支以及EC和CA3之间双向通路支持的记忆解码子系统，它提供了一种手段，通过这种手段，检索到的EC模式的CA3编码可以在EC上恢复该模式。该模型表明：1）在对皮层痕迹进行信息保留、结构提取编码的需求与对任意痕迹进行有效存储和回忆的需求之间存在权衡；2）在经历长时程增强的通路中，突触强度的长时程抑制对于保留信息至关重要；3）CA1区必须能够利用直接穿通通路突触中EC模式的相关性。
