Normandie Univ., UNICAEN, Univ Rennes, CNRS, UMR EthoS 6552, Caen, France.
Department of Psychology, University of Cambridge, Cambridge, UK.
Proc Biol Sci. 2021 Aug 25;288(1957):20211052. doi: 10.1098/rspb.2021.1052. Epub 2021 Aug 18.
Episodic memory, remembering past experiences based on unique what-where-when components, declines during ageing in humans, as does memory in non-human mammals. By contrast, semantic memory, remembering learnt knowledge without recalling unique what-where-when features, remains relatively intact with advancing age. The age-related decline in episodic memory likely stems from the deteriorating function of the hippocampus in the brain. Whether episodic memory can deteriorate with age in species that lack a hippocampus is unknown. Cuttlefish are molluscs that lack a hippocampus. We test both semantic-like and episodic-like memory in sub-adults and aged-adults nearing senescence ( = 6 per cohort). In the semantic-like memory task, cuttlefish had to learn that the location of a food resource was dependent on the time of day. Performance, measured as proportion of correct trials, was comparable across age groups. In the episodic-like memory task, cuttlefish had to solve a foraging task by retrieving what-where-when information about a past event with unique spatio-temporal features. In this task, performance was comparable across age groups; however, aged-adults reached the success criterion (8/10 correct choices in consecutive trials) significantly faster than sub-adults. Contrary to other animals, episodic-like memory is preserved in aged cuttlefish, suggesting that memory deterioration is delayed in this species.
情景记忆是基于独特的“什么-哪里-何时”成分来记住过去的经历，在人类衰老过程中会衰退，而非人类哺乳动物也是如此。相比之下，语义记忆是在不回忆独特的“什么-哪里-何时”特征的情况下记住所学的知识，它在年龄增长过程中相对保持完整。情景记忆随着年龄的增长而衰退，可能源于大脑中海马体功能的恶化。在没有海马体的物种中，情景记忆是否会随着年龄的增长而衰退尚不清楚。乌贼是缺乏海马体的软体动物。我们在亚成体和接近衰老（每组 6 只）的成年个体中测试了类似语义和类似情景的记忆。在类似语义的记忆任务中，乌贼必须学习食物资源的位置取决于一天中的时间。表现，以正确试验的比例来衡量，在不同年龄组之间是可比的。在类似情景的记忆任务中，乌贼必须通过检索过去事件的独特时空特征的“什么-哪里-何时”信息来解决觅食任务。在这个任务中，不同年龄组之间的表现是可比的；然而，成年个体达到成功标准（连续 10 次试验中有 8 次正确选择）的速度明显快于亚成体。与其他动物不同，类似情景的记忆在老年乌贼中得以保留，这表明这种记忆在该物种中退化被延迟了。
