Memories are thought to become more gist-like over time. Multiple related memories might form generalized memory representations, losing specific details but enhancing or retaining gist. The time course within which gist memory emerges, however, is the subject of less consensus. To address this question, we focused our design on four kinds of gist: inferential gist (relations extracted across non-contiguous events), statistical learning (regularities extracted from a series), summary gist (a theme abstracted from a temporally contiguous series of items), and category gist (characterization of a stimulus at a higher level in the semantic hierarchy). Seventy participants completed memory encoding tasks addressing these types of gist and corresponding retrieval tasks the same evening, the morning after, and one week later, as well as an MRI at a later time point. We found little evidence that gist slowly emerges over time or that gist traces are more resistant to forgetting than detail traces. Instead, we found that initial gist memory shortly after encoding was either retained over time or decayed. Inferential gist and statistical learning were retained over a week, whereas memory for category and summary gist decayed. We discuss several interpretations for differences between these two subtypes of gist. Individual differences in REM or slow-wave sleep and hippocampal volumes did not predict changes in memory for these four kinds of gist in a healthy young adult population.

人们认为随着时间的推移，记忆会变得更像要点。多个相关的记忆可能会形成广义的记忆表示，丢失特定的细节但增强或保留要点。然而，主旨记忆出现的时间过程是不太一致的主题。为了解决这个问题，我们将设计重点放在四种要点上：推理要点（从非连续事件中提取的关系）、统计学习（从系列中提取的规律性）、总结要点（从时间上连续的一系列项目中提取的主题）和类别要点（语义层次中更高级别的刺激特征）。70 名参与者在同一天晚上、第二天早上和一周后完成了针对这些类型的要点的记忆编码任务和相应的检索任务，以及稍后时间点的核磁共振。我们发现几乎没有证据表明随着时间的推移主旨会慢慢出现，或者主旨痕迹比细节痕迹更能抵抗遗忘。相反，我们发现编码后不久的初始主旨记忆要么随着时间的推移而保留，要么衰减。推理要点和统计学习保留了一周多，而对类别和总结要点的记忆衰退了。我们讨论了这两种主旨亚型之间差异的几种解释。快速眼动或慢波睡眠和海马体积的个体差异并不能预测健康年轻人群中这四种要点的记忆变化。我们发现编码后不久的初始主旨记忆要么随时间保留，要么衰减。推理要点和统计学习保留了一周多，而对类别和总结要点的记忆衰退了。我们讨论了这两种主旨亚型之间差异的几种解释。快速眼动或慢波睡眠和海马体积的个体差异并不能预测健康年轻人群中这四种要点的记忆变化。我们发现编码后不久的初始主旨记忆要么随时间保留，要么衰减。推理要点和统计学习保留了一周多，而对类别和总结要点的记忆衰退了。我们讨论了这两种主旨亚型之间差异的几种解释。快速眼动或慢波睡眠和海马体积的个体差异并不能预测健康年轻人群中这四种要点的记忆变化。