Katherine R. Mickley Steinmetz

The effect of arousal on the emotional memory network depends on valence

Some suggest that arousal is the essential element needed to engage the amygdala. However, the role of arousal in the larger emotional memory network may differ depending on the valence (positive, negative) of the to-be-remembered information. The goal of the current study was to determine the influence of arousal-based changes in amygdalar connectivity for positive and negative items. Participants were shown emotional and neutral pictures while they underwent a functional magnetic resonance imaging (fMRI) scan. The emotional pictures varied by valence (positive or negative) and arousal (high or low). Approximately 90minutes later, outside of the scanner, participants took a surprise recognition test. Effective connectivity analysis examined how arousal affected successful encoding activity. For negative information, arousal increased the strength of amygdala connections to the inferior frontal gyrus and the middle occipital gyrus, while for positive information arousal decreased the strength of these amygdala efferents. Further, while the effect of arousal on memory for positive information was restricted to amygdalar efferents, arousal had a more widespread effect for negative items, enhancing connectivity between other nodes of the emotional memory network. These findings emphasize that the effect of arousal on the connectivity within the emotional memory network depends on item valence.

The effects of valence and arousal on the neural activity leading to subsequent memory

This study examined how valence and arousal affect the processes linked to subsequent memory for emotional information. While undergoing an fMRI scan, participants viewed neutral pictures and emotional pictures varying by valence and arousal. After the scan, participants performed a recognition test. Subsequent memory for negative or high arousal information was associated with occipital and temporal activity, whereas memory for positive or low arousal information was associated with frontal activity. Regression analyses confirmed that for negative or high arousal items, temporal lobe activity was the strongest predictor of later memory whereas for positive or low arousal items, frontal activity corresponded most strongly with later memory. These results suggest that the types of encoding processes relating to memory (e.g., sensory vs. elaborative processing) can differ based on the affective qualities of emotional information.

The emotion-induced memory trade-off: More than an effect of overt attention?

Although it has been suggested that many effects of emotion on memory are attributable to attention, in the present study we addressed the hypothesis that such effects may relate to a number of different factors during encoding or postencoding. One way to look at the effects of emotion on memory is by examining the emotion-induced memory trade-off, whereby enhanced memory for emotional items often comes at the cost of memory for surrounding background information. We present evidence that this trade-off cannot be explained solely by overt attention (measured via eyetracking) directed to the emotional items during encoding. Participants did not devote more overt attention to emotional than to neutral items when those items were selectively remembered (at the expense of their backgrounds). Only when participants were asked to answer true/false questions about the items and the backgrounds—a manipulation designed to affect both overt attention and poststimulus elaboration—was there a reduction in selective emotional item memory due to an increase in background memory. These results indicate that the allocation of overt visual attention during encoding is not sufficient to predict the occurrence of selective item memory for emotional items.

The effects of trauma exposure and posttraumatic stress disorder (PTSD) on the emotion-induced memory trade-off

Many past examinations of memory changes in individuals with posttraumatic stress disorder (PTSD) have focused on changes in memory for trauma. However, it is unclear if these mnemonic differences extend beyond the memory of the trauma to memory for other positive and negative information and if they are specific to individuals with PTSD or extend to other individuals who have experienced trauma. The present study examined the influences of trauma exposure and PTSD on an effect that may parallel tunnel memory in PTSD: the emotion-induced memory trade-off, whereby emotional aspects of an experience are remembered at the expense of the nonemotional context. Three groups of participants (25 with current PTSD, 27 who had experienced trauma but did not have current PTSD, and 25 controls who had neither experienced significant trauma nor met criteria for current PTSD) were shown complex visual scenes that included an item (positive, negative, or neutral) placed on a neutral background. Forty-five minutes later, participants underwent a recognition memory test for the items and backgrounds separately. An emotion-induced memory trade-off was said to occur when there was a significant difference in item and background memory for emotional scenes, but not for neutral scenes. Results indicated that people with PTSD, like the other groups, were more likely to remember positive and negative items than neutral items. Moreover, people with PTSD exhibited a memory trade-off comparable in magnitude to that exhibited by the non-trauma control group. In contrast, trauma-exposed people without a current diagnosis of PTSD did not show a trade-off, because they remembered items within scenes better than their accompanying contexts not only for emotional but also for neutral scenes. These results suggest that (1) the effect of emotion on memory for visual scenes is similar in people with PTSD and control participants, and (2) people who have experienced trauma, but do not have PTSD, may have a different way of attending to and remembering visual scenes, exhibiting less of a memory trade-off than either control participants or people with PTSD.

The effect of emotional arousal and retention delay on subsequent-memory effects

Memory for emotional experiences often persists longer than memory for neutral experiences. The present study examined how encoding processes influence memory retention across 0.5- or 24-h delays and whether these processes differ between emotionally arousing and neutral information. Participants encoded items during an fMRI scan. Immediately following the scan, and again 24-h later, participants performed a recognition memory test. The results revealed that, for emotionally arousing information, most regions showed a correspondence to subsequent-memory performance that was at least as strong after the long delay as it was after the short delay. For neutral items, by contrast, many more regions, including portions of the hippocampus and lateral prefrontal cortex, showed a stronger correspondence to subsequent-memory performance after the short delay than the long delay. These results suggest that the processes engaged at the moment of encoding have a longer-lasting relation to subsequent memory for emotionally arousing information than for neutral information.

Neutral details associated with emotional events are encoded: evidence from a cued recall paradigm

ABSTRACT Enhanced emotional memory often comes at the cost of memory for surrounding background information. Narrowed-encoding theories suggest that this is due to narrowed attention for emotional information at encoding, leading to impaired encoding of background information. Recent work has suggested that an encoding-based theory may be insufficient. Here, we examined whether cued recall—instead of previously used recognition memory tasks—would reveal evidence that non-emotional information associated with emotional information was effectively encoded. Participants encoded positive, negative, or neutral objects on neutral backgrounds. At retrieval, they were given either the item or the background as a memory cue and were asked to recall the associated scene element. Counter to narrowed-encoding theories, emotional items were more likely than neutral items to trigger recall of the associated background. This finding suggests that there is a memory trace of this contextual information and that emotional cues may facilitate retrieval of this information.

Cross-cultural differences in item and background memory: examining the influence of emotional intensity and scene congruency

ABSTRACT After viewing a scene, individuals differ in what they prioritise and remember. Culture may be one factor that influences scene memory, as Westerners have been shown to be more item-focused than Easterners (see Masuda, T., & Nisbett, R. E. (2001). Attending holistically versus analytically: Comparing the context sensitivity of Japanese and Americans. Journal of Personality and Social Psychology, 81, 922–934). However, cultures may differ in their sensitivity to scene incongruences and emotion processing, which may account for cross-cultural differences in scene memory. The current study uses hierarchical linear modeling (HLM) to examine scene memory while controlling for scene congruency and the perceived emotional intensity of the images. American and East Asian participants encoded pictures that included a positive, negative, or neutral item placed on a neutral background. After a 20-min delay, participants were shown the item and background separately along with similar and new items and backgrounds to assess memory specificity. Results indicated that even when congruency and emotional intensity were controlled, there was evidence that Americans had better item memory than East Asians. Incongruent scenes were better remembered than congruent scenes. However, this effect did not differ by culture. This suggests that Americans’ item focus may result in memory changes that are robust despite variations in scene congruency and perceived emotion.

Cortisol and stimulus-induced arousal level differentially impact memory for items and backgrounds.

ABSTRACT Most studies examine the effects of stress on memory for visual information test memory for entire scenes. However, arousal levels may differentially influence memory for backgrounds as opposed to items. Participants encoded scenes that included a negative-high-arousal, negative-moderate-arousal, or neutral item on a neutral background. After a 30-minute (Experiment 1) or 48-hour delay (Experiment 2), participants underwent a stressor or control task while heart rate was recorded. A recognition memory task was then given with items and backgrounds presented separately. High-arousal images had a greater detriment in background memory than moderate-arousal images. Further, though there was evidence that change in cortisol level at retrieval was associated with impaired memory for items, it was not associated with detriments in background memory. Increased heart rate was associated with impaired memory for both items and backgrounds. This suggests that the level of sympathetic and cortisol reactivity differentially affects memory for items and backgrounds.