Do you remember...
One of the roles of
adrenaline is that of enhancing memory. As mentioned above, adrenaline is released in situations of
stress - be it mental or physical. The examples mentioned of do you remember are all instances of mental
stress. The mental stress is not always the result of a
tragedy (as
first kiss demonstrates).
Emotional events of any sort - weddings, child birth, and similar events will trigger a release of adrenaline. Most often, this is associated with "butterflies in the stomach" (think back to your first kiss, and the intensity of the memory will likely be directly related to the degree of butterflies).
There have been several experiments with laboratory rats regarding the formation of memory and its role with respect to adrenaline. The classic experiment deals with laboratory rats trying to find a platform submerged in water and having to swim to it - a stressful situation. This test is carried out several times, each time with the platform in the same place. The control group learns where the platform fairly quickly. Rats given an additional shot of adrenaline learned faster, while rats given a beta blocker that combats the effects of adrenaline are much slower to learn in this stressful situation.
A similar experiment was extended to humans. In this, some subjects were either given a beta blocker before viewing a series of images. These images were unpleasant to see (emotionally disturbing). Two weeks later, everyone was asked a series of questions based upon the images shown. The people given the beta blocker were not able to preform as well on the questions of the slides that were emotionally disturbing. Similar tests have been preformed with telling a story with story that had sad and stressful parts to it - those who received the beta blocker could not remember those elements of the story as well as those who received a placebo.
When the experience is stressful in some way, the adrenaline stimulates the amigdula (part of the brain that helps regulate memories) by way of the beta receptor (see beta blocker) on the vagus nerve (there is a large amount of research being done on memory improving drugs based upon this pathway - search Google for "vagus nerve memory" to see a sample of the reports). This extra stimulation in conjunction with a memory being formed directs the amigdula to store a strong memory rather than a weak one.
The usefulness of all the passions consist in their strengthening and prolonging in the soul thoughts which are good for it to conserve. And all the harm they can do consist in their strengthening and conserving these thoughts more than is necessary.
--Rene Descartes
http://www.outreach.nimh.nih.gov/speech_charney.htm
http://www.geocities.com/Nashville/2227/whyavoid.html
http://www.ihf.org/lecture/archive/mcgaugh.html