Division of Neuroscience and Experimental Psychology, School of Biological Sciences, The University of Manchester, Manchester, M13 9PL, United Kingdom
Laboratory for Clinical Neuroscience, Centre for Biomedical Technology, Universidad Politécnica de Madrid, Madrid 28223, Spain.
J Neurosci. 2022 Aug 17;42(33):6435-6444. doi: 10.1523/JNEUROSCI.1783-21.2022. Epub 2022 Jul 8.
To efficiently process information, the brain shifts between encoding and retrieval states, prioritizing bottom-up or top-down processing accordingly. Expectation violation before or during learning has been shown to trigger an adaptive encoding mechanism, resulting in better memory for unexpected events. Using fMRI, we explored (1) whether this encoding mechanism is also triggered during retrieval, and if so, (2) what the temporal dynamics of its mnemonic consequences are. Male and female participants studied object images, then, with new objects, they learned a contingency between a cue and a semantic category. Rule-abiding (expected) and violating (unexpected) targets and similar foils were used at test. We found interactions between previous and current similar events' expectation, such that when an expected event followed a similar but unexpected event, its performance was boosted, underpinned by activation in the hippocampus, midbrain, and occipital cortex. In contrast, a sequence of two unexpected similar events also triggered occipital engagement; however, this did not enhance memory performance. Taken together, our findings suggest that when the goal is to retrieve, encountering surprising events engages an encoding mechanism, supported by bottom-up processing, that may enhance memory for future related events. Optimizing the balance between new learning and the retrieval of existing knowledge is an ongoing process, at the core of human cognition. Previous research into memory encoding suggests experiencing surprise leads to the prioritization of the learning of new memories, forming an adaptive encoding mechanism. We examined whether this mechanism is also engaged when the current goal is to retrieve information. Our results demonstrate that an expectation-driven shift toward an encoding state, supported by enhanced perceptual processing, is beneficial for the correct identification of subsequent expected similar events. These findings have important implications for our understanding of the temporal dynamics of the adaptive encoding of information into memory.
为了有效处理信息，大脑在编码和检索状态之间转换，相应地优先考虑自下而上或自上而下的处理。在学习之前或期间的期望违背已被证明会触发适应性编码机制，从而对意外事件产生更好的记忆。使用 fMRI，我们探索了（1）这种编码机制是否也在检索过程中触发，如果是，（2）其记忆后果的时间动态是什么。男性和女性参与者研究了物体图像，然后，用新的物体，他们学习了线索和语义类别之间的关联。在测试中使用了符合规则（预期）和违反规则（意外）的目标以及类似的干扰物。我们发现先前和当前类似事件的期望之间存在相互作用，例如，当一个预期事件紧随一个类似但意外的事件时，它的表现会增强，这是由海马体、中脑和枕叶皮层的激活支持的。相比之下，两个意外的类似事件序列也会引发枕叶参与；然而，这并没有增强记忆表现。总的来说，我们的研究结果表明，当目标是检索时，遇到令人惊讶的事件会引发一种编码机制，该机制由自下而上的处理支持，这可能会增强对未来相关事件的记忆。优化新知识学习和现有知识检索之间的平衡是一个持续的过程，是人类认知的核心。先前关于记忆编码的研究表明，体验惊喜会导致新记忆学习的优先级提高，形成一种适应性编码机制。我们研究了当当前目标是检索信息时，这种机制是否也会被激活。我们的研究结果表明，一种期望驱动的向编码状态的转变，由增强的感知处理支持，有利于正确识别随后的预期类似事件。这些发现对我们理解信息自适应编码到记忆中的时间动态具有重要意义。
