The unpredictable past: spontaneous autobiographical memories outnumber autobiographical memories retrieved strategically

Involuntary autobiographical memories are spontaneously arising memories of personal events, whereas voluntary memories are retrieved strategically. Voluntary remembering has been studied in numerous experiments while involuntary remembering has been largely ignored. It is generally assumed that voluntary recall is the standard way of remembering, whereas involuntary recall is the exception. However, little is known about the actual frequency of these two types of remembering in daily life. Here, 48 Danish undergraduates recorded their involuntary versus voluntary autobiographical memories during a day using a mechanical counter. Involuntary memories were reported three times as frequently as voluntary memories. Compared to voluntary memories, they were associated less with problem solving and social sharing and more with day dreaming, periods of boredom, no reasons for remembering and predominantly came to mind during unfocused attention. The findings suggest that involuntary recall is a typical way of accessing the personal past.     

Conscious and unconscious discriminations between true and false memories

When subjects give higher confidence or memory ratings to a test word in a recognition test, do they simply raise their criterion without making better discrimination, or do they raise both criterion and true discrimination between the studied words (SW) and the lures? Given that previous studies found subjects’ false alarm responses to lures slower than to SW, and recognition latency inversely correlated with the confidence rating, can the latency difference between the lures and SW be accounted for by confidence or memory ratings? The present results showed that when subjects gave higher confidence or memory ratings, both their bias and sensitivity were raised, indicating that they could consciously distinguish the lures from the SW. However, a latency difference between true and false recognitions persisted after confidence and memory ratings were held constant, suggesting an unconscious source of discrimination between the two types of memory.     

The coherence of memories for trauma: Evidence from posttraumatic stress disorder

Participants with posttraumatic stress disorder (PTSD) and participants with a trauma but without PTSD wrote narratives of their trauma and, for comparison, of the most-important and the happiest events that occurred within a year of their trauma. They then rated these three events on coherence. Based on participants’ self-ratings and on naïve-observer scorings of the participants’ narratives, memories of traumas were not more incoherent than the comparison memories in participants in general or in participants with PTSD. This study comprehensively assesses narrative coherence using a full two (PTSD or not) by two (traumatic event or not) design. The results are counter to most prevalent theoretical views of memory for trauma.     

Associative learning performance is impaired in zebrafish (Danio rerio) by the NMDA-R antagonist MK-801

The zebrafish is gaining popularity in behavioral neuroscience perhaps because of a promise of efficient large scale mutagenesis and drug screens that could identify a substantial number of yet undiscovered molecular players involved in complex traits. Learning and memory are complex functions of the brain and the analysis of their mechanisms may benefit from such large scale zebrafish screens. One bottleneck in this research is the paucity of appropriate behavioral screening paradigms, which may be due to the relatively uncharacterized nature of the behavior of this species. Here we show that zebrafish exhibit good learning performance in a task adapted from the mammalian literature, a plus maze in which zebrafish are required to associate a neutral visual stimulus with the presence of conspecifics, the rewarding unconditioned stimulus. Furthermore, we show that MK-801, a non-competitive NMDA-R antagonist, impairs memory performance in this maze when administered right after training or just before recall but not when given before training at a dose that does not impair motor function, perception or motivation. These results suggest that the plus maze associative learning paradigm has face and construct validity and that zebrafish may become an appropriate and translationally relevant study species for the analysis of the mechanisms of vertebrate, including mammalian, learning and memory.     

Caudate nucleus-dependent response strategies in a virtual navigation task are associated with lower basal cortisol and impaired episodic memory

The present research examined the relationship between endogenous glucocorticoids, navigational strategies in a virtual navigation task, and performance on standard neuropsychological assessments of memory. Healthy young adult participants (N = 66, mean age: 21.7) were tested on the 4 on 8 virtual maze (4/8 VM) and standard neuropsychological tests such as the Rey-Osterrieth Complex Figure (RO) and the Rey Auditory Verbal Learning Task (RAVLT), which measure episodic memory. The 4/8 VM differentiates between navigational strategies, where participants either use a hippocampal-dependent spatial strategy by building relationships between landmarks, or a caudate nucleus-dependent stimulus–response strategy by automatizing a pattern of open and closed arms to learn the location of objects within the maze. Degree of stress was assessed by administering the Perceived Stress Scale (PSS) questionnaire. Cortisol samples were taken on two consecutive days upon waking, 30 min after waking, at 11 am, 4 pm, and 9 pm. There was a significant difference in basal levels of cortisol between spatial and response learners. Interestingly, response learners had significantly lower cortisol levels throughout the day. The two groups did not differ in terms of perceived stress as measured with the PSS questionnaire. Moreover, there was no significant correlation between PSS scores and salivary cortisol levels, indicating that the higher cortisol levels in the spatial group were not associated with greater perceived stress. In addition, participants who spontaneously used a spatial strategy performed significantly better on the RAVLT and RO. These data indicate that the cortisol levels in the spatial group may be optimal in terms of episodic memory performance whereas the cortisol levels in the response group may be associated with poorer memory. These results are suggestive of an inverted U-shaped curve describing the effects of basal levels of circulating cortisol on memory in young adults.     

‘I Remember When I Learned That!’ developmental and gender differences in children's memories of learning episodes

Eighty 4‐ to 9‐year‐old children answered factual knowledge questions in math, science and social studies during one‐on‐one interviews. Children indicated whether they had known or guessed each answer, and whether they (a) remembered the moment they learned the answer (episodic response) or (b) did not remember. For episodic responses, children provided memory narratives of learning episodes. One third of children's responses identified a learning episode. There was a developmental trend in which older children were more episodic than younger children, and when children knew and provided correct answers, there was a gender difference in which females were more episodic than males. Developmental and gender differences in the characteristics of memory narratives were also apparent. Copyright © 2010 John Wiley & Sons, Ltd.     

工作记忆负荷对注意捕获的影响研究

注意捕获研究对于探讨两种控制过程:自上而下的加工与自下而上的加工之间的关系具有重要的意义。本文通过检验不同工作记忆负荷对注意捕获的影响,探讨自上而下的认知控制对注意捕获的影响机制。本研究共包括二个实验:实验一比较了单、双任务条件对颜色干扰子注意捕获的影响;实验二探讨了不同工作记忆负荷对颜色干扰子注意捕获的影响。实验结果表明:工作记忆不仅在选择性注意任务中具有认知控制作用,而且这种作用能扩展到注意捕获现象中。注意捕获不是纯粹的刺激驱动的加工过程,它还受到自上而下的认知控制的调节。具体表现为,随着工作记忆负荷水平的增加,无关干扰子产生的注意捕获的程度增大。     

空间及言语工作记忆任务的情绪效应：来自ERP/ fMRI的证据

情绪与工作记忆的关系问题是情绪和认知研究领域中的子课题。根据加工效能理论, 负性情绪, 特别是焦虑对认知的影响通常被看作是通过影响工作记忆来完成的。因此, 探讨负性情绪是如何作用于工作记忆, 将有助于完善和发展情绪与认知的理论, 为心境障碍疾病的诊断、治疗及干预提供依据, 既具有学术价值又具有一定的临床意义。本论文在前人研究的基础上, 采用事件相关电位(ERP)和功能磁共振技术(fMRI), 系统地考察了情绪和工作记忆三个子成分(语音环路、视空间模板及中央执行器)间的关系。本论文抓住了当前的热点问题, 从情绪和认知的关系入手, 将脑成像、电生理和行为方面的研究有机结合, 将时间动态研究与空间定位研究相结合, 为情绪和工作记忆相互作用的神经机制提供独到的证据, 验证且发展了情绪和认知关系的奠基理论—— 加工效能理论。     

阿尔兹海默病患者中的范畴特异性语义记忆损伤

脑损伤可导致范畴特异性语义损伤, 即某一范畴的语义记忆选择性损伤或损伤更严重。阿尔兹海默病患者中的范畴特异性语义损伤可能来自不同范畴之间在熟悉度、词频、获得年龄、视觉复杂度、语义距离、加工要求以及所涉及的主要语义特征等方面的差别。然而, 有无生命范畴本身是否也是一个来源, 尚不清楚。进一步的研究不仅需要整合范畴途径和特征途径, 并区分语义记忆的存储和通达, 而且需要考查疾病严重程度如何影响语义记忆损伤模式。