熟悉性能够支持联结记忆:一体化编码的作用

双加工理论认为熟悉性和回想是支持情景记忆的两种基本加工过程。一般认为熟悉性和回想都可以支持项目记忆,但只有回想能够支持联结记忆。然而,一体化假说提出,当刺激材料在学习阶段得到一体化编码,形成一个单一、整合的表征时,熟悉性也能够支持联结记忆。以往研究主要利用实验材料的固有特征,或使用定义法、交互表象法来实现对刺激材料的一体化编码,然后通过配对联结再认范式或来源记忆范式验证一体化假说。神经成像研究发现,位于内侧颞叶的嗅周皮层能够支持编码阶段一体化表征的形成和基于熟悉性对一体化表征的提取。未来研究应克服以往研究中存在的方法学缺陷、从功能神经网络的角度考察一体化加工的脑神经机制、并注重一体化编码策略在特殊人群中的应用价值。     

注意分心对定义一体化编码的影响

通过考察编码阶段注意分心对定义一体化条件下联结记忆成绩的影响,探究定义一体化编码对注意资源的依赖程度。使用注意分心范式,在记忆编码过程操作无分心、奇偶分心和大小分心条件,比较不同注意条件下的联结记忆成绩。结果发现:与无分心条件相比,定义一体化下的联结记忆成绩在两种分心条件下没有显著变化,而造句下的联结记忆成绩在两种分心条件下显著降低。当前发现表明了定义一体化编码较少依赖于注意资源,这深化了对定义一体化编码机制的认识。     

整合对联结再认和项目再认的促进作用：“只有收益”观点

研究旨在探讨整合如何影响联结再认和项目再认及其加工过程。编码阶段要求被试学习复合词和非复合词, 提取阶段完成联结再认和项目再认测验。结果显示, 复合词比非复合词有更好的联结再认表现, 但在项目再认表现上两者之间没有显著的差异。ERP结果显示, 在联结再认上, 复合词诱发显著的FN400效应(与熟悉性加工有关)和LPC效应(与回想加工有关), 非复合词只诱发显著的LPC效应, 且复合词比非复合词有更大的LPC效应。在项目再认上, 复合词比非复合词诱发更大的FN400效应。总而言之, 整合在促进联结再认的同时并不会损害项目再认的表现, 支持了“只有收益”观点。     

从整合的角度看联结记忆中的项目再认

联结记忆由三种成分构成：项目1, 项目2以及项目1-项目2之间的联结, 其中, 对项目1和项目2的再认称之为项目再认, 而对项目1-项目2之间联结的再认称之为联结再认。双加工理论认为项目再认可以由熟悉性和回想加工来完成, 而联结再认只能由回想加工来完成。但近期有大量的研究发现：当要学习的项目对被整合为一个新的整体表征时, 熟悉性也能够支持联结再认。而关于整合对联结记忆中项目再认的研究较少, 总结已有研究提出两种观点：一种是“只有受益”观点(benefits-only)认为整合在增加联结再认的同时不影响项目再认; 另一种是“收支平衡”观点(costs and benefits)认为整合增加联结再认是以牺牲项目再认为代价的。未来研究应该关注整合对联结记忆中项目再认的影响及其神经机制, 了解整合对联结再认和项目再认的具体作用, 有助于针对具体记忆任务选择合适的编码方式来提高记忆表现。     

一体化促进联结记忆的作用机制：熟悉性和回想加工

当两个或两个以上项目进行一体化编码时, 熟悉性也能够支持联结再认, 这一观点已经得到大量研究证据的支持。然而, 关于一体化如何影响联结再认和构成联结的单个项目再认仍存在分歧。通过回顾现有研究发现：(1)一体化一致性是调节一体化与联结再认关系的重要因素; (2)认知资源有限和新/旧词语义相关性是影响一体化对项目再认作用的重要因素; (3)一体化的发生机制存在“项目假说”、“图式假说”以及“精细加工假说”三种可能的理论解释。未来研究不仅需要控制一体化一致性, 还可以比较不同一体化方式的作用大小以及探索一体化效应的毕生发展规律。     

Mood and Information Processing: When Happy and Sad Look the Same

Two studies were conducted to demonstrate that sad and happy moods can cause individuals to be similarly sensitive to the valence of observed stimuli with regard to how effortfully such stimuli are processed. In Study 1, individuals in whom a sad or happy mood had been induced unitized a behavior sequence less finely when its contents were neutral as opposed to positive. Individuals in a neutral mood state maintained a comparable level of unitization regardless of the valence of the behavior sequence. In Study 2, individuals in whom a sad or a happy mood had been induced processed the arguments in a persuasive communication more extensively when its contents were affectively uplifting rather than depressing. Sad individuals showed this pattern only if no prior affective expectation was provided. Taken together, these studies may fit with the notion that under certain conditions sad and happy individuals similarly decrease the amount of information processed from a neutral (Study 1) or depressing (Study 2), relative to a positive, stimulus.     

The impact of aging on associative memory for preexisting unitized associations

Aging is accompanied by a decline in associative memory that can, however, be attenuated when associations are unitized at encoding, that is, when they form an integrated entity. Unitization is thought to promote familiarity-based recognition memory, which is preserved in aging. We examined whether preexperimentally unitized associations (compound words (CWs)) do indeed reduce age differences in memory, and whether preexperimental unitization promotes familiarity. In Experiment 1, we assessed the memory of 20 young and 20 older participants for compound versus unrelated word pairs using a yes/no recognition test with Remember/Know/Guess judgments. In Experiment 2, we tested 20 young and 20 older participants using the same procedure, except for the use of a two-alternative forced-choice recognition paradigm, which is thought to enhance the contribution of familiarity. The results of both experiments corroborated the greater contribution of familiarity to recognition of unitized associations. In Experiment 1, however, the use of CWs did not attenuate the age-related associative decline. We suggest that preexisting knowledge associated with recombined compounds induced high absolute familiarity and illusory recollection, leading to high false-recognition rates for the older adults. By contrast, the two groups performed similarly across both conditions in Experiment 2. Thus, the forced-choice procedure facilitates the use of familiarity in such a way that it improves older adults’ associative memory to the level of young participants. These results suggest that the modulation of associative memory in aging by preexisting unitization varies according to methodological parameters, such as the nature of the lures and the test format.     

The effectiveness of unitization in mitigating age-related relational learning impairments depends on existing cognitive status

Binding relations among items in the transverse patterning (TP) task is dependent on the integrity of the hippocampus and its extended network. Older adults have impaired TP learning, corresponding to age-related reductions in hippocampal volumes. Unitization is a training strategy that can mitigate TP impairments in amnesia by reducing reliance on hippocampal-dependent relational binding and increasing reliance on fused representations. Here we examined whether healthy older adults and those showing early signs of cognitive decline would also benefit from unitization. Although both groups of older adults had neuropsychological performance within the healthy range, their TP learning differed both under standard and unitized training conditions. Healthy older adults with impaired TP learning under standard training benefited from unitized training. Older adults who failed the Montreal Cognitive Assessment (MoCA) showed greater impairments under standard conditions, and showed no evidence of improvement with unitization. These individuals’ failures to benefit from unitization may be a consequence of early deficits not seen in older adults who pass the MoCA.     

Misrecollection prevents older adults from benefitting from semantic relatedness of the memoranda in associative memory

Memory for episodic associations declines in aging, ostensibly due to decreased recollection abilities. Accordingly, associative unitization - the encoding of associated items as one integrated entity - may potentially attenuate age-related associative deficits by enabling familiarity-based retrieval, which is relatively preserved in aging. To test this hypothesis, we induced bottom-up unitization by manipulating semantic relatedness between memoranda. Twenty-four young and 24 older adults studied pairs of object pictures that were either semantically related or unrelated. Participants subsequently discriminated between intact, recombined and new pairs. We found that semantic relatedness increased the contributions of both familiarity and recollection in young adults, but did not improve older adults' performance. Instead, they showed associative deficits, driven by increased recollection-based false recognition. This may reflect a “misrecollection” phenomenon, in which older adults make more false alarms to recombined pairs with particularly high confidence, due to poorer retrieval monitoring regarding semantically-related associative probes.     

联结再认中双语者第二语言记忆优势效应

研究使用ERPs技术, 考察了双语者在联结再认中是否存在第二语言记忆优势效应。实验要求被试完成维吾尔语(L1)和汉语(L2)两类“学习-测试”任务。学习阶段要求被试学习混合呈现的复合词和无关词, 测验阶段要求被试区分“旧”、“重组”或“新”词对。行为结果发现：(1)复合词中, L2的正确率高于L1, L2的反应时快于L1; 无关词中, L2的正确率与L1无显著差异, 但L2的反应时快于L1。(2) 在L2和L1中, 复合词的正确率均高于无关词, 反应时均快于无关词。ERPs结果发现：(1)在高整合条件下, L2仅诱发了FN400效应, L1诱发了FN400效应和LPC效应; 在低整合条件下, L2和L1都只诱发了LPC效应。(2)在时间进程上, L2和L1分别在650 ms和900 ms完成联结关系的提取。上述结果表明, 在高整合条件下, 双语者在联结再认中存在L2记忆优势。此外, 实验结果也从双语角度证明了, 整合编码能促进熟悉性在维吾尔语联结再认中发挥作用。本研究结果的实践意义在于, 为我国少数民族学生习得国家通用语言文字提供了认知神经科学依据。