Elizabeth A. Kensinger

Memory enhancement for emotional words: are emotional words more vividly remembered than neutral words?

Individuals are more likely to remember negative information than neutral information. In the experiments reported here, we examined whether individuals were also more likely to remember details of the presentation of negative words, as compared with neutral words. In Experiment 1, the remember-know procedure was used to examine the effect of emotion on the vividness of an individual’s memory, showing thatremember responses were more frequently assigned to negative words than neutral words. In Experiment 2, a source memory paradigm was used, and again, evidence that individuals’ memories were more detailed for negative than for neutral words was found. In Experiments 3–6, we examined the relative contribution of valence and arousal, finding that both dimensions increased the vividness of remembered information (i.e., items with valence only and those that elicited arousal were better remembered than neutral information) but that the effect was greater for words that evoked arousal than for those with valence only. The results support a qualitative, as well as a quantitative, memory benefit for emotional, as compared with neutral, words.

Remembering the Details: Effects of Emotion:

Though emotion conveys memory benefits, it does not enhance memory equally for all aspects of an experience, nor for all types of emotional events. In this review, I outline the behavioral evidence for arousals focal enhancements of memory and describe the neural processes that may support those focal enhancements. I also present behavioral evidence to suggest that these focal enhancements occur more often for negative experiences than for positive ones. This result appears to arise because of valence-dependent effects on the neural processes recruited during episodic encoding and retrieval, with negative affect associated with increased engagement of sensory processes, and positive affect leading to enhanced recruitment of conceptual processes.

Remembering emotional experiences: the contribution of valence and arousal.

Emotional experiences can be described by two factors: valence (how negative or positive) and arousal (how calming or exciting). Although both dimensions appear to influence memory, they may do so via distinct mechanisms. The amygdala likely plays a specific role in modulating memory for arousing experiences, whereas non-amygdalar networks may be instrumental in enhancing memory for non-arousing positive or negative events.

Amygdala Activity Is Associated with the Successful Encoding of Item, But Not Source, Information for Positive and Negative Stimuli

It has been debated whether the link between amygdala activity and subsequent memory is equally strong for positive and negative information. Moreover, it has been unclear whether amygdala activity at encoding corresponds with enhanced memory for all contextual aspects of the presentation of an emotional item, or whether amygdala activity primarily enhances memory for the emotional item itself. In the present functional magnetic resonance imaging study, participants encoded positive and negative stimuli while performing one of two tasks (judgment of animacy or commonness). Amygdala activity at encoding was related to subsequent memory for the positive and negative items but not to subsequent memory for the task performed. Amygdala activity showed no relationship to subsequent-memory performance for the neutral items. Regardless of the emotional content of the items, activity in the entorhinal cortex corresponded with subsequent memory for the item but not with memory for the task performed, whereas hippocampal activity corresponded with subsequent memory for the task performed. These results are the first to demonstrate that the amygdala can be equally engaged during the successful encoding of positive and negative items but that its activity does not facilitate the encoding of all contextual elements present during an encoding episode. The results further suggest that dissociations within the medial temporal lobe sometimes noted for nonemotional information (i.e., activity in the hippocampus proper leading to later memory for context, and activity in the entorhinal cortex leading to later memory for an item but not its context) also hold for emotional information.

Sleep Preferentially Enhances Memory for Emotional Components of Scenes

Central aspects of emotional experiences are often well remembered at the expense of background details. Previous studies of such memory trade-offs have focused on memory after brief delays, but little is known about how these components of emotional memories change over time. We investigated the evolution of memory for negative scenes across 30 min, 12 daytime hours spent awake, and 12 nighttime hours including sleep. After 30 min, negative objects were well remembered at the expense of information about their backgrounds. Time spent awake led to forgetting of the entire negative scene, with memories of objects and their backgrounds decaying at similar rates. Sleep, in contrast, led to a preservation of memories of negative objects, but not their backgrounds, a result suggesting that the two components undergo differential processing during sleep. Memory for a negative scene develops differentially across time delays containing sleep and wake, with sleep selectively consolidating those aspects of memory that are of greatest value to the organism.

Processing emotional pictures and words: Effects of valence and arousal

There is considerable debate regarding the extent to which limbic regions respond differentially to items with different valences (positive or negative) or to different stimulus types (pictures or words). In the present event-related fMRI study, 21 participants viewed words and pictures that were neutral, negative, or positive. Negative and positive items were equated on arousal. The participants rated each item for whether it depicted or described something animate or inanimate or something common or uncommon. For both pictures and words, the amygdala, dorsomedial prefrontal cortex (PFC), and ventromedial PFC responded equally to all high-arousal items, regardless of valence. Laterality effects in the amygdala were based on the stimulus type (word 5 left, picture 5 bilateral). Valence effects were most apparent when the individuals processed pictures, and the results revealed a lateral/medial distinction within the PFC: The lateral PFC responded differentially to negative items, whereas the medial PFC was more engaged during the processing of positive pictures.

Effect of negative emotional content on working memory and long-term memory

In long-term memory, negative information is better remembered than neutral information. Differences in processes important to working memory may contribute to this emotional memory enhancement. To examine the effect that the emotional content of stimuli has on working memory performance, the authors asked participants to perform working memory tasks with negative and neutral stimuli. Task accuracy was unaffected by the emotional content of the stimuli. Reaction times also did not differ for negative relative to neutral words, but on an n-back task using faces, participants were slower to respond to fearful faces than to neutral faces. These results suggest that although emotional content does not have a robust effect on working memory, in some instances emotional salience can impede working memory performance.

Negative Emotion Enhances Memory Accuracy Behavioral and Neuroimaging Evidence

There have been extensive discussions about whether emotional memories contain more accurate detail than nonemotional memories do, or whether individuals simply believe that they have remembered emotional experiences more accurately. I review evidence that negative emotion enhances not only the subjective vividness of a memory but also the likelihood of remembering some (but not all) event details. I then describe neuroimaging evidence suggesting that engagement of emotion-processing regions (particularly the amygdala and orbitofrontal cortex) relates to the encoding and retrieval of details intrinsically linked to negative items.

Emotion and autobiographical memory.

Autobiographical memory encompasses our recollections of specific, personal events. In this article, we review the interactions between emotion and autobiographical memory, focusing on two broad ways in which these interactions occur. First, the emotional content of an experience can influence the way in which the event is remembered. Second, emotions and emotional goals experienced at the time of autobiographical retrieval can influence the information recalled. We discuss the behavioral manifestations of each of these types of interactions and describe the neural mechanisms that may support those interactions. We discuss how findings from the clinical literature (e.g., regarding depression) and the social psychology literature (e.g., on emotion regulation) might inform future investigations of the interplay between the emotions experienced at the time of retrieval and the memories recalled, and we present ideas for future research in this domain.

Aging, self-referencing, and medial prefrontal cortex

Abstract The lateral prefrontal cortex undergoes both structural and functional changes with healthy aging. In contrast, there is little structural change in the medial prefrontal cortex, but relatively little is known about the functional changes to this region with age. Using an event-related fMRI design, we investigated the response of medial prefrontal cortex during self-referencing in order to compare age groups on a task that young and elderly perform similarly and that is known to actively engage the region in young adults. Nineteen young (M age = 23) and seventeen elderly (M age = 72) judged whether adjectives described themselves, another person, or were presented in upper case. We assessed the overlap in activations between young and elderly for the self-reference effect (self vs. other person), and found that both groups engage medial prefrontal cortex and mid-cingulate during self-referencing. The only cerebral differences between the groups in self versus other personality assessment were found in somatosensory and motor-related areas. In contrast, age-related modulations were found in the cerebral network recruited for emotional valence processing. Elderly (but not young) showed increased activity in the dorsal prefrontal cortex for positive relative to negative items, which could reflect an increase in controlled processing of positive information for elderly adults.