The Neural Basis of Emotional Memory
High-school graduation.The death of a beloved pet.A particularly romantic evening. For most people, events like these—events that were emotional when they occurred— can be recalled in vivid detail even years later. Why is this? Why are these emotional events so well remembered?
The answer to these questions has several elements, one of them involving specific brain mechanisms (Figure P.7): One structure within the brain—the amygdala—seems to function more or less as an alarm system, evaluating the content of various inputs (or ideas or memories), and detecting whether that content is emotionally significant. If emotional content is detected, then various processes inside the amygdala activate
other brain sites, including sites within the hippocampus that are crucial for establishing long-term memories. Thus, emotional arousal leads—via the amygdala, modulating the activity of the hippocampus—to more complete and longer-lasting memories (McGaugh, 2003; Reisberg & Hertel, 2004).
Evidence for these claims comes from several types of research. In some cases, we can use brain scans to assess the moment-by-moment activity levels in the amygdala while someone is witnessing an emotional event. These scans show that the more activated the amygdala is during the event, the more likely the person is to have strong memories of the experience later on (Cahill, Babinsky, Markowitsch, & McGaugh, 1996).
Conversely, we can study the memories of people who have suffered damage to the amygdala—damage that causes a disorder known as Klüver-Bucy syndrome. These individuals seem overall to be less emotional—less likely to show fear, less likely to be aggressive, and so on—thus confirming the role of the amygdala in shaping our emotional lives. But, in addition, these individuals do not show the enhancement of memory for emotional events that we can so easily observe in most other people. Without the amygdala, the processes that produce this enhancement cannot function; individuals with Klüver-Bucy syndrome thus show little difference between how they remember significant emotional episodes and how they remember much more mun-dane events (Buchanan & Adolphs, 2004).
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