Dissociation is the essence of trauma. The overwhelming experience is split off and fragmented, so that the emotions, sounds, images, thoughts, and physical sensations related to the trauma take on a life of their own.
Trauma tends to get fragmented and compartmentalized, stored in different parts of our brain. This is why it can take a long time for any trauma survivor to make sense of what they have been through. The sights, the sounds, the physical sensations, the emotions associated with trauma can be cut off from the more rational parts of our brain. That is why it is so important to treat trauma on the level of both mind and body because it is the only way to begin to create a cohesive narrative and heal.