The style of the editing in Memento reflects Leonard's condition of short term memory loss. The non linear editing gives the impression of the story being told in two different tenses. The fact the parts of the story are parallel yet are from different aspects, contrasts with the typical way of editing. The introduction of the film is split into colour and black and white scenes, the black and white scenes hint that they are flashbacks yet it isn't confirmed, this is an enigma code; the audience want to know what has happened, and why he shot 'Teddy' in the head.
The film opens on an extreme close up of a Polaroid picture of a crime scene; a body and blood all over the wall, it appears to be what you would typically expect a crime scene to look like, this being a cultural shortcut instantly indicates that somebody has been shot. The polaroid has a mans thumb holding the picture. As the credits roll you see the photo being shaken as the image gets lighter, this immediately implies the clip is being played backwards which is a cultural code as you know instantly it is a Polaroid; which you shake to make the image appear. It starts to fade, this links to Leonard having short term memory loss; this is then a symbolic code. The scene continues to run backwards, showing what has happened up to the point of the man being shot. It goes back in slight slow motion, which emphasises how fast it happened when the scene switches to playing forword and the man is shot. The music being played is non-diagetic, it builds tension to the point of the man being shot where the music cuts and you hear the gunshot.
It then goes to an extreme close up of the characters eyes, which illustrates that we are seeing the story through his eyes, this is enforced by him narrating the scene as there is various extreme close-ups, it makes it harder for the audience to focus on the setting. It is then made clear he is in a motel room; the image of him in the motel room again is a cultural code, mainly obvious to the western world, which is the target audience. It is also obvious that it is a flashback as it is in black and white. The mixture of him voicing over the scene, the gray scale filming and the extreme close up indicates something out of the ordinary with this character, that the way he thinks could be in great detail like the clip shows; it makes the audience believe there potentially could be something wrong with him e.g amnesia. This is an enigma code as it creates a story and hooks the audience in, wanting to know more. Linking the two scenes together is the fact that all the clips we've seen are very short which reflects his short term memory, it implied that as the clips are quite intense that he is angry about his short term memory condition.
The narration then continues to Leonard making a payment to the hotel receptionist, it is made clear he 'isn't all there' as he is reminded by the receptionist that they have previously had the conversation. It is noticable that he is also staying in a temporary home, which reflects his amnesia. The character who was shot in the opening sequence then appears at the hotel, which immediatley tells the audience that the film is not showing in chronological order, this is another enigma code; the audience will want to know why they aren't being shown the sequence of events in the correct order. It becomes evident that we are being shown the colour clips in reverse.
The introduction of the film then progresses in the manner of switching from black and white to colour, the impression that it gives is that the colour scenes are being shown in reverse, and the black and white scenes are being shown in chronological order, this gives the audience an an enigma code to ultimatley work out where the two sets of clips will meet. It also gives an insight to Leonard's disability, as we (the audience) are trying to work out his story just as much as he is.