When someone tells me they understand what happened to them - they can describe it clearly, give it context, even explain why it makes sense that they feel the way they do - and yet still find themselves overwhelmed by a smell, a tone of voice, or the quality of light in a particular room, they are often confused. If I understand it, they ask, why does my body still react as if it's happening right now?
The answer lies in how traumatic memory is stored. It does not work the way people assume memory works.
Two Memory Systems
Memory is not a single system. The brain organises different types of experience through different neural pathways, and these pathways do not always communicate with each other in the ways we might expect.
Explicit memory - also called declarative memory - is what most people think of when they think of remembering. It is conscious, verbal, narrative. It allows us to locate an experience in time: this happened then, in that place, when I was that age. It gives events a beginning, a middle, and an end. It allows us to say: that was the past. It is not happening now.
Implicit memory is different. It operates below conscious awareness and does not carry a timestamp. It encodes what the nervous system learned - patterns of threat and safety, physical responses, emotional states - without organising them into a story with a clear temporal location. Implicit memory does not say: this happened then. It encodes simply: this happened. And when something in the current environment resembles the original conditions, it activates as if those conditions are present now.
Traumatic memory is predominantly encoded in implicit systems.
What Sensory Encoding Means in Practice
Bessel van der Kolk's research has been foundational in demonstrating that trauma is stored differently than ordinary experience. Rather than being integrated into coherent narrative, traumatic memory tends to be preserved in fragmented, sensory form: body sensations, visual images, sounds, smells, emotional states that arrive without context. These fragments are not organised around a story. They are encoded as raw experience - the way the body felt, the sound that was present, the physical environment of threat.
This is why people with trauma histories frequently report that their memories do not feel like memories in the ordinary sense. They do not recall an event from a distance. The experience arrives - in the body, in the senses - with a quality of immediacy that can be disorienting and frightening, particularly for those who do not understand what is happening neurologically.
The implicit memory system does not timestamp. It encodes: this happened. Not: this happened then.
Why Triggers Feel Present-Tense
When an individual with a trauma history encounters a cue that resembles the original threat - a tone of voice, a physical sensation, a particular smell or quality of sound - the amygdala activates before the prefrontal cortex has had time to contextualise the information.
The amygdala is the brain's threat detection centre. It operates rapidly and automatically, scanning incoming sensory information for anything that resembles known danger. It does not wait for conscious evaluation. By the time the prefrontal cortex - the region responsible for reasoning, perspective-taking, and temporal orientation - begins to process the situation, the body is already responding. The heart rate has changed. The muscles have tensed. Attention has narrowed. The nervous system is already in a state of defensive activation.
This is not an overreaction. It is not weakness or irrationality. It is the nervous system doing precisely what it was designed to do: prioritising survival over accuracy. The problem is not that the system is malfunctioning. The problem is that it is responding to a signal from the past as if that signal is a present threat - because the implicit memory system has no mechanism for distinguishing between then and now.
This is why a person can understand their history completely at the cognitive level - can describe it articulately, can recognise that they are safe, can hold all the relevant context - and simultaneously experience physiological responses that feel unconnected to that understanding. The cognitive system and the implicit memory system are operating in parallel, and they do not automatically synchronise.
What This Means for Treatment
If traumatic memory is stored primarily in implicit, sensory, body-based systems, then an approach to healing that relies primarily on verbal narrative - on talking about the past, constructing meaning, developing insight - will have significant limits. Language can organise experience. Narrative can provide context and coherence. Insight is genuinely valuable. But none of these processes directly access or modify the implicit memory networks where the traumatic encoding lives.
Integration requires engaging the systems where the memory is actually held.
This is the theoretical foundation underlying approaches such as EMDR (Eye Movement Desensitisation and Reprocessing), Somatic Experiencing, and Sensorimotor Psychotherapy. Each of these methods works at the level of the body and the implicit memory system - not only at the level of cognition and narrative. EMDR uses bilateral stimulation to facilitate the reconsolidation of traumatic memories within the brain's normal memory processing networks. Somatic Experiencing works with the body's incomplete defensive responses, allowing the nervous system to complete cycles of activation and discharge that were interrupted at the time of the original experience. Sensorimotor Psychotherapy integrates body awareness directly into the therapeutic process, recognising that the body holds what the mind cannot yet put into words.
None of these approaches dismisses the value of understanding. Cognitive work, meaning-making, and narrative integration remain important parts of trauma processing - particularly in later stages, when the nervous system has sufficient regulation to approach difficult material without being overwhelmed by it. But they work most effectively in combination with approaches that engage the body and the implicit memory systems, not as a substitute for them.
The Significance of Not Knowing Why
One of the most clinically important implications of understanding traumatic memory in this way is what it offers to people who cannot explain their own reactions. Many individuals with trauma histories carry significant shame about the gap between what they know and how they respond. They understand that they are safe. They understand that the person in front of them is not their abuser. They understand that the situation is not the same. And they still respond as if it is - and cannot understand why their understanding makes no difference to their nervous system.
The neurobiological reality is that this gap is expected. It is not a sign of inadequate insight, insufficient willpower, or psychological weakness. It is a reflection of how memory works when the original experience exceeded the nervous system's capacity for integration. The body is not failing to listen to the mind. It is operating through a different system, one that was shaped before conscious understanding had the opportunity to intervene.
The body reacts before cognition intervenes. This is not a flaw. It is architecture - and understanding it is where healing begins.
Toward Integration
Healing from trauma does not require eliminating the body's responses or achieving a state in which triggers no longer occur. It requires, over time, creating enough internal resource and nervous system regulation that the implicit memory networks can be approached and gradually reconsolidated - so that the past can begin to be experienced as past, rather than as an ongoing present-tense emergency.
This is slow work. It moves at the pace the nervous system can tolerate. It requires safety, relational trust, and titrated exposure to difficult material rather than flooding. It requires approaches that speak to the body, not only to the thinking mind.
But it is available. And for many people, understanding why the body responds the way it does - understanding the neuroscience, not just the story - is itself a significant step. It replaces shame with information. It replaces self-criticism with curiosity. And it opens the possibility of a different relationship with one's own nervous system: not as something broken that needs to be controlled, but as something shaped by experience that can, with the right support, begin to learn that the danger has passed.