I found this article in Frontiers, an online science publication I subscribe to about the effects of high and low stress on the brain. The amygdala plays a big role in how we process stress, and it is very active during high stress situations.
So, if the amygdala is highly active, we cannot remember as well as when it is at a normal functioning level. This part of the brain is one of the lit up areas when a person with Post Traumatic Stress Disorder(PTSD) is having an episode, therefore our memory after the event is impaired.
It is my experience that this impairment lasts for about a week before normal functioning comes back online, unless another trigger is encountered. From the time of the last triggered episode to when the brain feels normal in terms of memory function again is about a week.
I don’t get much accomplished during that time period, and at first it was very frustrating, until I experienced it often enough to finally learn not to fight it. The healing happens faster when we are relaxed and not producing toxic chemicals in our bodies that impede the process.
(Modified to change title on Sept 23,2011 by adding a paragraph before the link and a paragraph at the end to complete the thought. Also added image by pandayuliu from Flickr.com .)