Emotional Arousal and Memory Binding

王蓓

◆ABSTRACT ： Binding various features of an event together and maintaining these connections in memory is an essential component of episodic memories. Previous theories make contradictory predictions about the effects of emotional arousal on memory binding. In this article， I review evidence for both arousal-impaired and arousal-enhanced memory binding and explain these contradictory findings using an object-based framework.

1 Existing Theories about Arousal and Memory Binding

Most research on emotional memory in humans has focused on item memory rather than on memory for context or associations. However， two theories that make opposing predictions about emotional arousal and memory binding have emerged. Opposing Predictions Arousal-Enhances-Binding Hypothesis MacKay and colleagues posit that arousing stimuli trigger emotional reactions that prioritize the process of binding those stimuli to their context. Research by MacKays group has focused on the differences in memory for taboo words and for neutral words. According to their priority-binding theory， when a word is seen during a list-learning task， a binding node is primed to form connections between the episodic context and the words meaning. When an arousing word appears in a rapidly presented sequence of words （e.g.， 200ms per word）， activation of other currently primed binding nodes is delayed until binding for the higher-priority emotional item is complete （Hadley & MacKay，2006）. This theory is potentially consistent with studies showing that， after viewing a sequence of words one at a time， people tend to have better memory for the color or location of emotional or arousing words than for the color or location of neutral words from the sequence （MacKay & Ahmetzanov， 2005; MacKay et al.，2004）; however， the priority-binding hypothesis does not make direct predictions about the slower word-presentation rates used in some of the studies showing the same effect.

2 Arousal and Memory Binding in Initial Encoding and Short-Term

Retention

Binding features of objects to create coherent representations starts with initial perception. If a person is quickly shown a scene， how well can he or she correctly bind the various features to their appropriate sources？ For example， how likely is someone to correctly perceive blotches of red and green in the scene as a red apple and a green leaf rather than as a green apple and a red leaf （Treisman & Schmidt， 1982）？ Focused Attention Is Required for Perceptual Binding Treismans feature-integration theory proposes that features such as color and shape are registered automatically and in parallel in the visual field， but that to bind features within an object （such as a red apple） together， the viewer must focus attention on that object（Treisman，1999）.

3 Summary for Arousal and Long-Term Consolidation of

Binding

As reviewed earlier， there are at least a couple of plausible hypotheses about how arousal affects long-term memory consolidation of bound representations. However， these hypotheses suffer from a lack of relevant （and confound-free） research with human participants. Kleinsmith and Kaplans findings that memory consolidation was enhanced for associations with arousing items are confounded with order effects. In fact， studies that did not have the order confound typically found the opposite effect： Associations with other items are more likely to be forgotten for arousing items than for neutral items. More promising is the hypothesis， based on animal research indicating opposing effects of long-term stress on the amygdala versus hippocampus and prefrontal brain regions， that arousal could lead to enhanced consolidation of item memory but impaired consolidation of memory binding. However， work is needed to extend these findings to instances of acute （rather than chronic） arousal and to human episodic memory. In doing this work， researchers should pay attention to the distinction between within-object and between-object binding， as benefits for consolidation may accrue depending on whether an associated feature is considered to bepart of the same object as the arousing item.

4 Conclusions

Making and retaining associations among various elements of experience is essential for episodic memory. As I outlined at the outset of the article， two previous theories make opposing pre-dictions about the effects of arousal on memory binding. These two theories focus on different aspects of arousal. MacKay and colleagues priority-binding theory posits that arousing stimuli get priority over non-arousing stimuli in their access to binding resources when the stimuli are first perceived; their theory thus focuses on the effects of arousing versus non-arousing items.

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