Jan. 31, 2005 -- Ever wonder why some memories can stay vivid for years while others fade with time? The answer is emotion.
When the emotions are aroused, the brain takes note. It stores as much detail as possible about the emotion-filled event, wiring it for quick recall. That emotion-charged memory can be summoned at a moment's notice, even after a long time has passed.
That's true for positive and negative emotions, say Duke University's Florin Dolcos and colleagues. Their report appears in the early online edition of Proceedings of the National Academy of Sciences.
The study included nine young women who were about 26 years old on average. Compared with men, "women are physiologically more reactive to emotional stimuli and more likely to report intense emotional experiences," say the researchers.
First, the women were shown 180 pictures that were evenly divided between pleasant, neutral, and unpleasant images. The women rated how pleasant (or not) they thought the images were. While the women looked at the pictures, the researchers performed brain scans on them.
About a year later, the women returned for a follow-up test. They saw the old images again, along with 90 new ones (30 pleasant, 30 neutral, and 30 unpleasant). Brain scans were performed again.
As the images appeared, the women pressed a 'remember' key indicting they remembered the image and specifically recalled seeing it a year earlier and knowing its details. Or they could press a 'know' key meaning the image looked familiar but they couldn't remember details about it. Lastly, they could say the image was new.
The women were better at recognizing the emotional pictures than the neutral ones.
Two brain regions were active during successful retrieval of memory: the amygdala and the hippocampus. The same areas also successfully encode emotional memories, say the researchers.
The results show that this region of the brain plays a role in emotional memory, not only for successful storing of the memory, but also for its successful retrieval.
The power of emotional memories may date back a long time. For our long-ago ancestors, the thrill of finding food or the fear of prowling predators could have started the pattern, say the researchers.