Laboratoire Epilepsies et Cognition, INSERM U-751, Université de la Méditerranée, Faculté de médecine La Timone, 27 Bd Jean Moulin, 13385 Marseille cedex 5, France.
Brain. 2011 Mar;134(Pt 3):816-31. doi: 10.1093/brain/awr002.
Several experiments carried out with a subset of patients with temporal lobe epilepsy have demonstrated normal memory performance at standard delays of recall (i.e. minutes to hours) but impaired performance over longer delays (i.e. days or weeks), suggesting altered long-term consolidation mechanisms. These mechanisms were specifically investigated in a group of five adult-onset pharmaco-sensitive patients with temporal lobe epilepsy, exhibiting severe episodic memory complaints despite normal performance at standardized memory assessment. In a first experiment, the magnitude of autobiographical memory loss was evaluated using retrograde personal memory tasks based on verbal and visual cues. In both conditions, results showed an unusual U-shaped pattern of personal memory impairment, encompassing most of the patients' life, sparing however, periods of the childhood, early adulthood and past several weeks. This profile was suggestive of a long-term consolidation impairment of personal episodes, adequately consolidated over 'short-term' delays but gradually forgotten thereafter. Therefore, in a subsequent experiment, patients were submitted to a protocol specifically devised to investigate short and long-term consolidation of contextually-bound experiences (episodic memory) and context-free information (semantic knowledge and single-items). In the short term (1 h), performance at both contextually-free and contextually-bound memory tasks was intact. After a 6-week delay, however, contextually-bound memory performance was impaired while contextually-free memory performance remained preserved. This effect was independent of task difficulty and the modality of retrieval (recall and recognition). Neuroimaging studies revealed the presence of mild metabolic changes within medial temporal lobe structures. Taken together, these results show the existence of different consolidation systems within declarative memory. They suggest that mild medial temporal lobe dysfunction can impede the building and stabilization of episodic memories but leaves long-term semantic and single-items mnemonic traces intact.
几项针对颞叶癫痫患者亚组进行的实验表明，患者在标准回忆延迟（即几分钟到几小时）时记忆表现正常，但在较长延迟（即几天或几周）时表现不佳，提示存在长期巩固机制改变。这些机制在一组五名成年起病、药物敏感的颞叶癫痫患者中得到了具体研究，这些患者尽管在标准化记忆评估中表现正常，但存在严重的情景记忆主诉。在第一项实验中，使用基于言语和视觉提示的逆行个人记忆任务评估自传体记忆丧失的程度。在两种条件下，结果均显示出个人记忆损伤的异常 U 形模式，涵盖了患者大部分的生活经历，但儿童期、成年早期和过去几周的记忆未受影响。这种模式提示个人经历的长期巩固受损，在“短期”延迟内得到充分巩固，但此后逐渐遗忘。因此，在随后的实验中，患者接受了一项专门设计的方案，以研究上下文相关经验（情景记忆）和无上下文信息（语义知识和单项记忆）的短期和长期巩固。在短期（1 小时），无上下文和上下文相关记忆任务的表现均完整。然而，在 6 周的延迟后，上下文相关的记忆表现受损，而无上下文的记忆表现仍然完好。这种影响与任务难度和检索方式（回忆和识别）无关。神经影像学研究显示内侧颞叶结构内存在轻度代谢变化。综合来看，这些结果表明在陈述性记忆中存在不同的巩固系统。它们提示轻度内侧颞叶功能障碍可能会阻碍情景记忆的建立和稳定，但会使长期的语义和单项记忆痕迹保持完整。
