Nadel L, Samsonovich A, Ryan L, Moscovitch M
Department of Psychology, University of Arizona, Tucson, USA.
Hippocampus. 2000;10(4):352-68. doi: 10.1002/1098-1063(2000)10:4<352::AID-HIPO2>3.0.CO;2-D.
Hippocampal-neocortical interactions in memory have typically been characterized within the "standard model" of memory consolidation. In this view, memory storage initially requires hippocampal linking of dispersed neocortical storage sites, but over time this need dissipates, and the hippocampal component is rendered unnecessary. This change in function over time is held to account for the retrograde amnesia (RA) gradients often seen in patients with hippocampal damage. Recent evidence, however, calls this standard model into question, and we have recently proposed a new approach, the "multiple memory trace" (MMT) theory. In this view, hippocampal ensembles are always involved in storage and retrieval of episodic information, but semantic (gist) information can be established in neocortex, and will survive damage to the hippocampal system if enough time has elapsed. This approach accounts more readily for the very long RA gradients often observed in amnesia. We report the results of analytic and connectionist simulations that demonstrate the feasibility of MMT. We also report a neuroimaging study showing that retrieval of very remote (25-year-old) memories elicits as much activation in hippocampus as retrieval of quite recent memories. Finally, we report new data from the study of patients with temporal lobe damage, using more sensitive measures than previously the case, showing that deficits in both episodic and spatial detail can be observed even for very remote memories. Overall, these findings indicate that the standard model of memory consolidation, which views the hippocampus as having only a temporary role in memory, is wrong. Instead, the data support the view that for episodic and spatial detail the hippocampal system is always necessary.
记忆中的海马体-新皮层相互作用通常是在记忆巩固的“标准模型”中进行描述的。按照这种观点，记忆存储最初需要海马体将分散的新皮层存储位点连接起来，但随着时间推移，这种需求会消失，海马体部分就变得不再必要。功能随时间的这种变化被认为可以解释海马体损伤患者中常见的逆行性遗忘（RA）梯度。然而，最近的证据对这个标准模型提出了质疑，我们最近提出了一种新方法，即“多重记忆痕迹”（MMT）理论。按照这种观点，海马体集合始终参与情景信息的存储和提取，但语义（要点）信息可以在新皮层中建立，如果经过足够长的时间，即使海马体系统受损，语义信息也能留存。这种方法更容易解释在遗忘症中经常观察到的非常长的RA梯度。我们报告了分析和联结主义模拟的结果，这些结果证明了MMT的可行性。我们还报告了一项神经影像学研究，该研究表明，提取非常久远（25年前）的记忆在海马体中引发的激活与提取相当近期的记忆时一样多。最后，我们报告了对颞叶损伤患者研究的新数据，这些数据采用了比以往更敏感的测量方法，结果表明，即使是非常久远的记忆，也能观察到情景和空间细节方面的缺陷。总体而言，这些发现表明，将海马体在记忆中仅视为具有临时作用的记忆巩固标准模型是错误的。相反，数据支持这样一种观点，即对于情景和空间细节而言，海马体系统始终是必要的。
