Cogdell-Brooke Lucy, Stampacchia Sara, Jefferies Elizabeth, Violante Inês R, Thompson Hannah E
School of Psychology, University of Surrey, UK.
Department of Psychology, University of York, UK; Neuroimaging and Innovative Molecular Tracers, University of Geneva, Switzerland.
Neuropsychologia. 2020 Mar 16;140:107392. doi: 10.1016/j.neuropsychologia.2020.107392. Epub 2020 Feb 13.
Semantic Aphasia (SA) patients have difficulty accessing semantic knowledge in both verbal and non-verbal tasks appropriately for the current context. Automatically activated semantic knowledge overwhelms the system, because it is no longer able to inhibit interference from dominant meanings in order to select weaker alternatives. Episodic memory, like semantic memory, requires control to select relevant memories amongst competing episodes. For example, our memory for what we ate for breakfast last Saturday is affected by competition from numerous other breakfast meals eaten on other days. Where one is unable to guide retrieval, we may rely on automatically activated knowledge about "breakfast foods", and therefore experience false memories. Brain systems that support semantic control are also implicated in episodic control, and therefore deficits in semantic control are likely to cause more widespread problems. Despite this, nearly all research to date focuses on semantic performance alone. This study explored the impact of this semantic impairment on episodic recall. We used a verbal and non-verbal episodic memory task: participants remembered nursery rhymes in the verbal condition and logos and their associated products in the visual condition (e.g. bowl of cereal and coco-pops). For both tasks, we manipulated a) congruency with pre-existing knowledge (e.g. expectancy of trials: baa baa blackbuild - instead of sheep) and b) whether these trial types were blocked by congruency or mixed, as well as (c) distractor strength. If SA patients experience overwhelming automatic activation, they should find incongruent items more difficult to suppress, particularly when presented in an unpredictable task format. A total of 13 SA patients were compared to 33 controls across three experiments. In line with our predictions, SA patients found it more difficult to retrieve episodic memories which were in conflict with pre-existing semantic knowledge. This was true across modalities. Moreover, these deficits were accentuated when the congruency was presented in a mixed fashion, and so unpredictable across trials. Evidence of these episodic control impairments in SA cases supports the idea of a shared mechanism for semantic and episodic memory control.
语义性失语症（SA）患者在言语和非言语任务中，都难以根据当前情境恰当地获取语义知识。自动激活的语义知识使系统不堪重负，因为它不再能够抑制来自主导意义的干扰，以便选择较弱的替代意义。情景记忆与语义记忆一样，需要控制才能在相互竞争的情景中选择相关记忆。例如，我们对上周六早餐吃了什么的记忆，会受到其他日子吃的众多其他早餐的竞争影响。当一个人无法引导检索时，我们可能会依赖自动激活的关于“早餐食物”的知识，从而产生错误记忆。支持语义控制的脑系统也与情景控制有关，因此语义控制缺陷可能会导致更广泛的问题。尽管如此，迄今为止几乎所有研究都仅关注语义表现。本研究探讨了这种语义损伤对情景回忆的影响。我们使用了言语和非言语情景记忆任务：在言语条件下，参与者记住童谣；在视觉条件下，参与者记住标志及其相关产品（例如一碗麦片和可可泡芙）。对于这两个任务，我们操纵了：a）与现有知识的一致性（例如试验预期：咩咩黑建筑——而不是羊）；b）这些试验类型是按一致性进行分组还是混合呈现，以及（c）干扰物强度。如果SA患者经历压倒性的自动激活，他们应该会发现不一致的项目更难抑制，尤其是当以不可预测的任务形式呈现时。在三个实验中，共将13名SA患者与33名对照组进行了比较。与我们的预测一致，SA患者发现检索与现有语义知识相冲突的情景记忆更加困难。跨模态情况都是如此。此外，当一致性以混合方式呈现，且在试验中不可预测时，这些缺陷会更加明显。SA病例中这些情景控制损伤的证据支持了语义和情景记忆控制存在共享机制的观点。
