Emotional memories are not all created equal: evidence for selective memory enhancement

Human brain imaging studies have shown that greater amygdala activation to emotional relative to neutral events leads to enhanced episodic memory. Other studies have shown that fearful faces also elicit greater amygdala activation relative to neutral faces. To the extent that amygdala recruitment is sufficient to enhance recollection, these separate lines of evidence predict that recognition memory should be greater for fearful relative to neutral faces. Experiment 1 demonstrated enhanced memory for emotionally negative relative to neutral scenes; however, fearful faces were not subject to enhanced recognition across a variety of delays (15 min to 2 wk). Experiment 2 demonstrated that enhanced delayed recognition for emotional scenes was associated with increased sympathetic autonomic arousal, indexed by the galvanic skin response, relative to fearful faces. These results suggest that while amygdala activation may be necessary, it alone is insufficient to enhance episodic memory formation. It is proposed that a sufficient level of systemic arousal is required to alter memory consolidation resulting in enhanced recollection of emotional events.     

Failure of positive but not negative emotional valence to enhance memory in schizophrenia

Abnormalities in the integration of emotion and cognition have long been considered hallmark characteristics of schizophrenia. Study authors used a well-established emotional memory model from the neuroscience literature to assess the facilitative impact of emotional valence of information on long-term memory consolidation in schizophrenia. Participants with schizophrenia (n=33) indicated somewhat higher levels of emotional intensity in response to emotional images than did healthy (n=28) participants. However, when recognition memory was tested 24 hr later, schizophrenia participants did not show enhancement of memory for positive images as was found in healthy participants. Their memory enhancement for negative images did not differ from that of healthy participants. Correlations between self-reported physical and social anhedonia were significantly inversely correlated with intensity ratings of positive stimuli during the encoding phase for healthy participants but were negligible for schizophrenia participants. These results suggest a failure to adequately integrate positive emotional experience in memory consolidation processes in schizophrenia participants, despite appropriate initial response to positive stimuli, which may contribute to symptoms such as anhedonia by reducing the long-term impact of positive experiences in motivating hedonic behavior in day-to-day life.     

Moderate-to-vigorous intensity cycling exercise immediately after visual learning enhances delayed recognition memory performance

A single bout of acute aerobic exercise has been shown to improve long-term memory, though it is unclear if exercise before learning or after learning is optimal for memory enhancement. Although some research has demonstrated that exercise before learning is ideal, investigations have consistently shown that acute arousal post-learning is a powerful memory enhancer. Therefore, the purpose of this investigation was to compare the effects of self-perceived hard cycling before or after learning on recognition memory for emotional and neutral images, and examine the relationship between central noradrenergic activity and memory performance. Seventy-two males and females (18–35 years of age) participated in this between-subjects study. Participants were randomly assigned to one of the following groups: exercise before learning, exercise after learning, and control. Participants in the exercise groups engaged in 20 min of cycling at a rating of perceived exertion (RPE) of 15 (“hard”) on the Borg RPE scale before or after viewing a series of 90 pleasant, unpleasant, and neutral images (30 each). Participants in the control group engaged in no exercise before or after image viewing. At several time points throughout the experiment, saliva was collected to measure salivary alpha amylase (sAA), a marker of central noradrenergic activity. One-week later, recognition memory was assessed where participants viewed 180 images (90 new) and had to identify which images were previously viewed. Participants in the exercise after learning group had significantly higher recognition memory compared to the control group, but this was not seen with exercise before learning. sAA was not correlated with memory in any group, though it did increase during exercise. These results demonstrate that acute self-perceived hard cycling post-learning, but not pre-learning, improves recognition memory, though this was unrelated to the exercise-induced increase in central noradrenergic activity as measured in saliva.     

不同情绪背景下来源记忆的ERPs研究*

使用事件相关电位(ERP)技术和测试来源记忆的多键范式,探讨不同情绪效价背景下来源提取的认知神经机制。学习阶段,同时呈现汉字和3种效价情绪图片(重叠);测验阶段,只呈现汉字,要求被试进行四键判断：旧字且背景为中性,旧字且背景为正性,旧字且背景为负性,新字。结果发现：在提取阶段,刺激呈现后300~500 ms,3种情绪背景下来源判断正确项目和来源判断错误项目都比新项目诱发了更正的ERPs(即都存在新旧效应),这一结果反映出刺激呈现后300~500 ms 是一个早期的项目提取阶段,它独立于来源提取。并且,在中性背景下,两种新旧效应没有差别;而在正性和负性背景下,来源判断正确项目的新旧效应显著大于来源判断错误项目。说明相比于中性背景,情绪背景下被试可能更早对来源信息产生熟悉感。在500~650 ms,3种情绪背景下都存在来源判断正确项目的新旧效应,在来源判断错误项目和新项目之间没有显著差异,来源正确与来源错误有显著的新旧效应差异,但二者在头皮分布上是类似的,这反映了晚期的来源提取过程。同时来源正确的新旧效应在这两个时段有显著不同的头皮分布,表明这两个时段有不同加工过程。另外,在500~650 ms,存在显著的情绪效应,正性背景下正确判断来源诱发的ERPs比中性和负性背景下的更正,而且来源判断错误条件下没有情绪效应。综上所述,来源正确和来源错误可能仅仅反映了大脑激活在量上的不同,并不能推断两者存在质的差异;大脑神经活动的早期不仅反映了对记忆项目的熟悉性,而且也受情绪效应的影响,500 ms之后大脑神经活动反映的是对记忆项目回想的过程,这一回想过程也与情绪效应有关,受到情绪效应的调节。     

Memory errors on emotional lures: Is it possible to mistake a positive stimulus for a negative one?

This study examined whether it is possible for people to mistakenly recognise a stimulus of one emotional valence through exposure to stimuli with another emotional valence that share orthographical relatedness. Across three experiments, the recognition error rates for emotionally distinctive lures were lower than for nondistinctive ones. The reduction in memory errors generalises to different types of emotional distinctiveness: emotional lures from neutral words, neutral lures from emotional words, and lures that have opposite valence from the studied ones. However, emotionally distinctive lures were still prone to memory errors. Repeated exposure to orthographically related items resulted in higher recognition error rates than lures without such exposure. Implications for everyday memory are discussed.     

Post-encoding emotional arousal enhances consolidation of item memory,but not reality-monitoring source memory

The current study examined whether the effect of post-encoding emotional arousal on item memory extends to reality-monitoring source memory and, if so, whether the effect depends on emotionality of learning stimuli and testing format. In Experiment 1, participants encoded neutral words and imagined or viewed their corresponding object pictures. Then they watched a neutral, positive, or negative video. The 24-hour delayed test showed that emotional arousal had little effect on both item memory and reality-monitoring source memory. Experiment 2 was similar except that participants encoded neutral, positive, and negative words and imagined or viewed their corresponding object pictures. The results showed that positive and negative emotional arousal induced after encoding enhanced consolidation of item memory, but not reality-monitoring source memory, regardless of emotionality of learning stimuli. Experiment 3, identical to Experiment 2 except that participants were tested only on source memory for all the encoded items, still showed that post-encoding emotional arousal had little effect on consolidation of reality-monitoring source memory. Taken together, regardless of emotionality of learning stimuli and regardless of testing format of source memory (conjunction test vs. independent test), the facilitatory effect of post-encoding emotional arousal on item memory does not generalize to reality-monitoring source memory.     

Revelation without presentation: Counterfeit study list yields robust revelation effect

This study explores the revelation effect, a recognition memory phenomenon that occurs when test items (or related items) are specially processed before recognition judgment. These revealed items, whether targets or lures, receive a positive response bias. Although the effect occurs across various conditions, it has not been shown to occur when participants make judgments unrelated to episodic memory. We investigated whether the effect would occur when a recognition decision was nominally one of episodic memory, but when a complete episodic event had not occurred. Specifically, participants listened to noise that allegedly masked a list of words (in fact, no words existed). A revelation effect occurred with this pseudo-subliminal procedure, suggesting that the revelation effect need not rely on stimuli recalled through episodic memory but only a specific event to recall. The effect did not occur when participants simply guessed whether words were on an unheard list or made semantic judgments.     

When the half-full glass is appraised as half empty and memorised as completely empty: Mood-congruent true and false recognition in depression is modulated by salience

Since the 1980s a large body of empirical effort has been devoted to mood-congruent memory (MCM) biases in clinical depression. Whereas there is broad, albeit not unequivocal, evidence that depressive patients retain negative-valenced memory items better than neutral material, few studies have investigated false memories in depression. In a pilot study we gathered support for both enhanced true and false memory for emotional material in depression. The present study aimed to extend these preliminary findings. In view of investigations suggesting that arousing and meaningful stimuli have facilitated access to memory, personal salience was considered a moderator for MCM. In the present study 21 depressed and 22 healthy participants were presented six false memory lists dealing with neutral, negative, and positive themes. At recognition, each item had to be appraised for its degree of valence subsequent to an old–new judgement. Pre-categorised and subjective valence did not discriminate groups. However, relative to controls depressed patients showed both more veridical as well as false recognition for items that concurrently elicited higher salience ratings in patients. In contrast, group differences in recognition performance did not significantly affect salience ratings. Results indicate that salience modulates MCM and may account for discrepancies in the literature.     

Effect of positive emotion on consolidation of memory for faces: The modulation of facial valence and facial gender

Studies have shown that emotion elicited after learning enhances memory consolidation. However, no prior studies have used facial photos as stimuli. This study examined the effect of post-learning positive emotion on consolidation of memory for faces. During the learning participants viewed neutral, positive, or negative faces. Then they were assigned to a condition in which they either watched a 9-minute positive video clip, or a 9-minute neutral video. Then 30 minutes after the learning participants took a surprise memory test, in which they made “remember”, “know”, and “new” judgements. The findings are: (1) Positive emotion enhanced consolidation of recognition for negative male faces, but impaired consolidation of recognition for negative female faces; (2) For males, recognition for negative faces was equivalent to that for positive faces; for females, recognition for negative faces was better than that for positive faces. Our study provides the important evidence that effect of post-learning emotion on memory consolidation can extend to facial stimuli and such an effect can be modulated by facial valence and facial gender. The findings may shed light on establishing models concerning the influence of emotion on memory consolidation.     

When the half-full glass is appraised as half empty and memorised as completely empty: mood-congruent true and false recognition in depression is modulated by salience

Since the 1980s a large body of empirical effort has been devoted to mood-congruent memory (MCM) biases in clinical depression. Whereas there is broad, albeit not unequivocal, evidence that depressive patients retain negative-valenced memory items better than neutral material, few studies have investigated false memories in depression. In a pilot study we gathered support for both enhanced true and false memory for emotional material in depression. The present study aimed to extend these preliminary findings. In view of investigations suggesting that arousing and meaningful stimuli have facilitated access to memory, personal salience was considered a moderator for MCM. In the present study 21 depressed and 22 healthy participants were presented six false memory lists dealing with neutral, negative, and positive themes. At recognition, each item had to be appraised for its degree of valence subsequent to an old-new judgement. Pre-categorised and subjective valence did not discriminate groups. However, relative to controls depressed patients showed both more veridical as well as false recognition for items that concurrently elicited higher salience ratings in patients. In contrast, group differences in recognition performance did not significantly affect salience ratings. Results indicate that salience modulates MCM and may account for discrepancies in the literature.     

Emotion-induced modulation of recognition memory decisions in a Go/NoGo task: Response bias or memory bias?

In recognition memory tests for words, items with negative emotional meaning are more often classified as “old” compared to neutral items, whether or not they are in fact old. Two accounts for this bias have been offered: One proposes that emotions disrupt retrieval and response monitoring processes (executive control account), the other proposes that emotions cause illusory feelings of remembering (memory bias account). We addressed this issue by varying the target signal in a Go/NoGo variant of a recognition memory task for negative, neutral, and positive words and faces: One group of participants was asked to respond to old items whereas the other group was asked to respond to new items. Results showed that the “Go-for-old” group showed the typical emotion-induced response bias shift for both positive and negative words, while the “Go-for-new” group showed the opposite pattern. Results were nonsignificant for faces, but went into the same direction. The findings are clearly inconsistent with the executive control account and speak for a genuine memory illusion induced by emotional arousal.     

Effects of oral cortisol treatment in healthy young women on memory retrieval of negative and neutral words

Studies in rodents have demonstrated that glucocorticoids enhance memory consolidation but impair delayed memory retrieval. Similar findings have been reported in humans. Emotional items are better remembered than neutral items. However, it is unknown if emotional valence influences the effects of cortisol on retrieval. In this double-blind crossover study, 16 healthy women learned a wordlist containing 15 neutral and 15 negative words. Delayed recall was tested 5h later. Cortisol administered before recall testing significantly reduced retrieval (p<.01). Exploratory follow-up analysis revealed that cortisol significantly impaired retrieval of negative words (p<.01), while having no significant effect on neutral words (p=.47). The current findings could suggest that emotional material is especially sensitive to the memory modulating effects of stress hormones.     

The impact of post-learning sleep vs. wakefulness on recognition memory for faces with different facial expressions

A beneficial effect of sleep after learning, compared to wakefulness, on memory formation has been shown in many studies using a variety of tasks. However, none of these studies has specifically addressed recognition memory for faces so far. The recognition of familiar faces, together with the extraction of emotional information from facial expression, is a fundamental cognitive skill in human everyday life, for which specific neural systems and mechanisms of processing have been developed. Here, we investigated the role of post-learning sleep for later recognition memory for neutral, happy, and angry faces. Twelve healthy subjects, after judging the emotional valence of the faces in the evening (learning phase), either slept normally in the subsequent night, with sleep recorded polysomnographically (sleep condition), or remained awake (wake condition) according to a cross-over design. Recognition testing took place in the second evening after learning, i.e. after a further night of regular sleep spent at home. Sleep after learning, compared to wakefulness, enhanced memory accuracy in recognition memory. This effect was independent of the emotional valence of facial expression. The response criterion at recognition testing did not differ between sleep and wake conditions. The amount of non rapid eye movement (NonREM) sleep during post-learning sleep correlated positively with memory accuracy at recognition testing, while time in REM sleep was associated with a speeded responding to the learned faces. Results suggest that face recognition, despite its dependence on specialized brain systems, nevertheless relies on the general neural mechanisms of sleep-associated memory consolidation.     

Affective orientation influences memory for emotional and neutral words

Memory is better for emotional words than for neutral words, but the conditions contributing to emotional memory improvement are not entirely understood. Elsewhere, it has been observed that retrieval of a word is easier when its attributes are congruent with a property assessed during an earlier judgment task. The present study examined whether affective assessment of a word matters to its remembrance. Two experiments were run, one in which only valence assessment was performed, and another in which valence assessment was combined with a running recognition for list words. In both experiments, some participants judged whether each word in a randomized list was negative (negative monitoring), and others judged whether each was positive (positive monitoring). We then tested their explicit memory for the words via both free recall and delayed recognition. Both experiments revealed an affective congruence effect, such that negative words were more likely to be recalled and recognized after negative monitoring, whereas positive words likewise benefited from positive monitoring. Memory for neutral words was better after negative monitoring than positive monitoring.Thus, memory for both emotional and neutral words is contingent on one's affective orientation during encoding.     

Incidental retrieval of emotional contexts in post-traumatic stress disorder and depression: an fMRI study

In the present study, we used fMRI to assess patients suffering from post-traumatic stress disorder (PTSD) or depression, and trauma-exposed controls, during an episodic memory retrieval task that included non-trauma-related emotional information. In the study phase of the task neutral pictures were presented in emotional or neutral contexts. Participants were scanned during the test phase, when they were presented with old and new neutral images in a yes/no recognition memory task. fMRI results for the contrast between old and new items revealed activation in a predominantly left-sided network of cortical regions including the left middle temporal, bilateral posterior cingulate, and left prefrontal cortices. Activity common to all three groups when correctly judging pictures encoded in emotional contexts was much more limited. Relative to the control and depressed groups the PTSD group exhibited greater sensitivity to correctly recognised stimuli in the left amygdala/ventral striatum and right occipital cortex, and more specific sensitivity to items encoded in emotional contexts in the right precuneus, left superior frontal gyrus, and bilateral insula. These results are consistent with a substantially intact neural system supporting episodic retrieval in patients suffering from PTSD. Moreover, there was little indication that PTSD is associated with a marked change in the way negatively valenced information, not of personal significance, is processed.     

Emotion's influence on memory for spatial and temporal context

Individuals report remembering emotional items vividly. It is debated whether this report reflects enhanced memory accuracy or a bias to believe emotional memories are vivid. We hypothesised emotion would enhance memory accuracy, improving memory for contextual details. The hallmark of episodic memory is that items are remembered in a spatial and temporal context, so we examined whether an item's valence (positive, negative) or arousal (high, low) would influence its ability to be remembered with those contextual details. Across two experiments, high-arousal items were remembered with spatial and temporal context more often than low-arousal items. Item valence did not influence memory for those details, although positive high-arousal items were recognised or recalled more often than negative items. These data suggest that emotion does not just bias participants to believe they have a vivid memory; rather, the arousal elicited by an event can benefit memory for some types of contextual details.     

Emotion's influence on memory for spatial and temporal context

Individuals report remembering emotional items vividly. It is debated whether this report reflects enhanced memory accuracy or a bias to believe emotional memories are vivid. We hypothesized emotion would enhance memory accuracy, improving memory for contextual details. The hallmark of episodic memory is that items are remembered in a spatial and temporal context, so we examined whether an item's valence (positive, negative) or arousal (high, low) would influence its ability to be remembered with those contextual details. Across two experiments, high-arousal items were remembered with spatial and temporal context more often than low-arousal items. Item valence did not influence memory for those details, although positive high-arousal items were recognized or recalled more often than negative items. These data suggest that emotion does not just bias participants to believe they have a vivid memory; rather, the arousal elicited by an event can benefit memory for some types of contextual details.     

Sleep facilitates consolidation of positive emotional memory in healthy older adults

ABSTRACT

Evidence has demonstrated that sleep-related memory consolidation declines in ageing. However, little is known about age-related changes to sleep-related emotional memory consolidation, especially when considering the positivity effect observed in older adults. In the present study, we sought to explore whether there is a positive emotional bias in sleep-related memory consolidation among healthy older adults. Young and older adults were randomly assigned either into a sleep or wake condition. All participants encoded positive, negative, and neutral stimuli and underwent recognition tests immediately (test 1), after a 12-hour sleep/wake interval (test 2), and 3 days after test 2 (test 3). Results showed that age-related differences of sleep beneficial effect were modulated by emotion valence. In particular, sleep selectively enhanced positive memory in older adults, while in young adults sleep beneficial effect was manifested in neutral memory. Moreover, the sleep beneficial effect can be maintained at least 3 days in both young and older adults. These findings suggest that older adults had preserved but positive bias of sleep-related memory consolidation, which could be one of the underlying mechanisms for their generally better emotional well-being in daily life. These findings highlight the dynamic interplay among sleep and emotional memory in older adults.     

老年人错误记忆的情绪效价和时间效应

基于信号检测论的框架, 考察不同的情绪效价以及时间间隔如何交互影响老年人在图片再认任务中的辨别力(d′)和判断标准(β), 进而影响其错误记忆。以21名老年人(女性14名)为被试, 平均年龄67.17 ± 5.03岁。根据中国老年人对国际情绪图片库(International Affective Picture System, IAPS)中图片评定的情绪参数, 选出积极、消极和中性图片各60张作为学习材料。另选积极、消极和中性图片各30张作为每次再认测验的干扰材料, 并且两次再认测验的干扰材料不同。短时间隔条件让老年人在图片记忆编码半个小时后完成对图片的再认测验; 长时间隔条件则为在三周后完成对图片的再认测验。结果发现: 1)在短时间隔条件下, β和d′共同影响虚报率; 而在长时间隔条件下, 只有β影响虚报率, d′不影响虚报率; 2)无论是在短时还是长时间隔条件下, 积极图片与消极图片的判别力d′都没有显著差别; 3)在短时间隔条件下, 老年人对消极图片的β更低、虚报率更高; 在长时间隔条件下, 老年人对积极图片的β更低、虚报率更高。研究结果表明: 老年人的错误记忆受判别力d′和判断标准β的影响。情绪效价通过作用于老年人的反应倾向(判断标准β)、而非记忆质量(判别力d′)来影响其错误记忆。时间间隔可以调节情绪效价对老年人判断标准β和错误记忆的作用, 使之随时间发生反转。老年人的“积极效应”在错误记忆中可能表现为随着时间的流逝, 老年人更愿意将积极信息报告为经历或学习过的信息。     

情绪对连续事件定向遗忘的影响

本研究采用项目法定向遗忘范式以中性和负性连续事件的视频为实验材料, 通过2个实验考察了情绪对连续事件定向遗忘的影响, 并进一步探讨了情绪对细节记忆和要义记忆的定向遗忘的影响。结果发现, 情绪可以消除细节记忆的定向遗忘效应, 而仅有要义记忆的定向遗忘效应则主要受到事件连续性而非情绪的影响。