Collective memory: “The North remembers”
What is behind this quote from the TV serie Game of Thrones? In this fiction, when a wrong is made to a part of the North’s population, the whole region remembers the event and held a grudge on the persons responsible. I have noticed similar situations happen for us. When a traumatic event occurs (for example a terrorist attack), we have of course the victims or the witnesses who suffered directly, but there are the rest of the people, the rest of the nation, who is affected too. After such events, the population is stressed, tensed. Everyone has it in mind. With time, this feeling might still be present in some people’s mind, but it faded. I have been wandering how this phenomenon works and evolves with these indirect victims. This is what we are going to explore in this article talking about collective memory.
What is a psychological trauma?
This kind of trauma have a large variety of origins divided in two categories. Situations that are a threat to physical integrity to yourself or to someone else (grief, sexual abuse, victim or witness of a traumatic event) or a threat to psychological integrity (attachment troubles, harassment, repetitive humiliation, extended poverty). This induce an extreme stress state which will overload the brain and will circuit break the emotional circuit, leading to a traumatic memory . These are serious consequences and shouldn’t be treated lightly.
Normal response versus abnormal response
The emotional circuit is controlled by the limbic system which is involved in emotions and memory. What interest us mostly is the amygdala, the core of the unconscious emotional memory. This system can deal with unexpected danger usually but when suffering a psychological trauma, the response is different.
In a normal response, when a danger occur, the stimulus reaches the thalamus. From the thalamus, we distinguish two ways. First, the short way (thalamo-amygdalian) which triggers the amygdala and give an automatic response to the danger. Then, the long way (thalamo-cortico-amygdalian) analyses the situation and the danger to modulate the activation of the amygdala and adapt our response. The situation created an emotional response that has been treated and can be classed in the center of memory (hippocampus).
In an abnormal response, due psychological trauma, the modulation of the amygdala is impossible. Therefore, the emotional response is always maximal with an important production of cortisol and adrenaline. This overproduction becomes toxic for the heart (because of the adrenaline) which can lead heart attacks and for the brain (because of the glycemic due to cortisol) which results in neurones death especially in the hippocampus.
But our organism has a safe switch. Same as in an electric circuit, the system circuit breaks. This allows the amygdala to shut down and, even though the trauma is still ongoing, the stress lowers. However the amygdala’s shut down leads to two consequences. First, stimuli are treated without any emotion, physical or psychological suffering which gives a sensation of unreality, confusion, depersonalisation, called dissociation. The other consequence comes from the interaction between amygdala and hippocampus and can cause partial or total memory loss either from the traumatic event or even before it. It is also the origin of the traumatic memory responsable of flashbacks and panic attacks among other things.
Nation as one person
The two previous parts explain what happens to the victims of traumatic events but this article is focused on the rest of the people, the ones who haven’t lived it. Nevertheless, there was a purpose explaining all this. Indeed, what happens to those people is the exact same thing. They experience a psychological trauma even though the intensity is lessened . They go through the same symptoms described here.
The reason has already been given in the last article . A nation exists as an entity which people belong to. Therefore, when an extraordinary and dramatic event occur and target people, it touches not only the victims but the nation, meaning everyone feels concerned and are affected. This will feed this collective memory coming from a succession of events occurring in a country defines the society to which the concerned persons belong.
The perspective of a specific group define what is perceived of a major event. Let’s take an example: World War II. Ask to people from different nationalities to cite events from it. An American will talk about Normandy landings, Pearl Harbor, Hiroshima and Nagasaki bombing. A French will cite the occupation itself, the battle of Verdun but will omit Pearl Harbor. A Russian will focus on the battle of Stalingrad. 
This group effect applies at different scales. There is the world scale, for all of us as a specie, in case of an extinction threat. There is the national scale, where we have a national identity. We can think to others scales such as the city scale, the family scale, the close social group scale (with your friends), the work scale (with your coworkers). In the end, there is as many groups as there is a combination of people. Each group has its own collective memory. This comes from the fact that collective memory is directly linked to your individual memory.
Individual memory versus collective memory
A person is a member of several social groups (family, friends, coworkers, acquaintances) and is a part of each of this groups memory. That person may not remember everything about a specific event lived by that group. Some details of the event are missing like the weather that day. Nonetheless, the other people of this group fill the gaps and create a complete memory of this event. From that, the memory of each participant feed the memory of the others. 
The same phenomenon occurs when you do not live the event yourself but you feel concerned (if it affected a friend, a relative or someone of your nation). The memory of the witnesses and the victims, what they tell, what they lived, feeds your own memory and becomes your own.
A fading memory
All collective memories have a spatial anchor. Let it be, the location of a terrorist attack, a war or the house you grew up with your siblings, the cinema you go with your friends. The location receives the print of the group and becomes tight to it. It is not because a memory is intrinsically linked to a place but because the group attaches the memory to the place, to make it live on.
But the limits that you can reach when you look further in the collective memory of group depends on the groupe itself, due to the limits of the individual memories. Collective memory fades as the individual memory fades. While people remains in the group to make the memories live on, it perdures. When there is no-one left to remember, the collective memory ends and become a part of History.
 Psychotraumatismes, Dr Muriel Salmona, https://www.memoiretraumatique.org/psychotraumatismes/introduction.html
 Arthur G. Neal. National Trauma and Collective Memory: Extraordinary Events in the American Experience. M.E. Sharpe, 2005. ISBN 9780765615817
 All You Need Is Science, The emergence of borders
 The Power of Collective Memory, https://www.scientificamerican.com/article/the-power-of-collective-memory/
 Maurice Halbwachs. La mémoire collective. 1950. http://dx.doi.org/doi:10.1522/cla.ham.mem1
Licata L.; Mercy A. Collective Memory, Social Psychology of. International Encyclopedia of the Social& Behavioural Sciences (Second Edition). 2015, Pages 194-199. https://doi.org/10.1016/B978-0-08-097086-8.24046-4