The amygdala is the alarm bell of the brain, involved in fear and threat detection. It asks the question, “is this dangerous?” It is important in helping to survive when there is actual danger or threat and it prunes itself to the environment. When it becomes overactive, it causes the nervous system stuck in high alert. This overactivation sends constant “fight, flight, freeze, or fawn” signals and floods the body with stress chemicals, even when no present-day threat exists.

The hippocampus is like the long term storage unit responsible for learning memory, explicit, declarative, autobiographical memory. The hippocampus is what places experiences in time, sequence, and context, so you know what happened first, what came after, and that something belongs to the past rather than the present.

When trauma happens, this function gets disrupted. Memories can be stored in fragments, body sensations, or raw sensory impressions instead of a coherent storyline. This is why flashbacks or intrusive memories feel like they’re happening right now—because the hippocampus has lost its ability to anchor them in time.

The hippocampus is also covered in cortisol receptors. When trauma is intense or ongoing, those receptors get flooded by stress hormones. Too much cortisol can impair the hippocampus, making it harder to encode and retrieve memory accurately. That’s why in complex trauma, memories may feel blurry, missing, or scrambled, while the body still holds onto the intensity of the experience.

The hippocampus also has a regulating relationship with the amygdala, acting similar to an air conditioner. Normally, the hippocampus helps calm it down by cross-checking with memory: “This looks similar, but it isn’t the same thing. You’re safe now.”

But when the hippocampus is dysregulated, that communication breaks down. Instead of sending a calming signal, it may send a generalized danger cue.

• The amygdala asks: “Is this dangerous?”

• A healthy hippocampus responds: “No, this is just a reminder, not a threat.”

• A dysregulated hippocampus may respond: “Yes, this is the same as before! Sound the alarm!”

This is how trauma creates false alarms, where the body and nervous system react to present-day triggers as if the original danger is happening again.

EMDR helps the hippocampus come back online. Through bilateral stimulation and reprocessing, the hippocampus can re-anchor traumatic memories in their proper time and place, telling the amygdala: “That was then, this is now.” This shift allows memories to be integrated into the broader life story, no longer overwhelming or frozen, but part of a larger narrative that the nervous system can hold with more clarity and regulation.

The hypothalamus communicates directly with the pituitary gland and adrenal glands (the HPA axis), setting off cascades of stress hormones, cortisol and adrenaline. Chronic trauma and stress dysregulates this system, resulting in either constant revved up hyperarousal, constantly flooding the system, or burned out, exhausted, and blunted. This is why trauma survivors may experience the feeling that their bodies are betraying them, swinging between hyperactivation and collapse.

The ACC is like the inner “bridge” of self-regulation. It is a cortical brain region involved in cognitive control, self-regulation, error detection, and conflict monitoring. When trauma and stress, and worry dominate, the ACC goes offline. That means that there is no ability to pause, reflect, regulate emotion, redirect attention, and feel a sense of control in the present. When the AAC is offline, it contributes to a defaulted sense of “I can’t control this. I’m not really here.”

The insula helps us sense the inner world of the body’s felt state (interoception). Supports interoceptive awareness (the ability to sense internal body states). Trauma disrupts insula activity, leading to difficulties noticing or trusting body sensations, a key factor in dissociation or emotional overwhelm. The Insula works directly with the Cingulate to interpret these messages and respond to them.

The Default Mode Network (DMN) is a large-scale brain system that turns on when the mind is not engaged in an external task. It’s active during daydreaming, mind-wandering, self-reflection, and imagining possibilities. In a balanced state, the DMN is not harmful.

In trauma, the DMN loops on cycles of negative self-beliefs, intrusive memories, and shame spirals, instead of fluid thought exploration.

When the DMN dominates due to stress, depression, anxiety, or trauma, the anterior cingulate cortex (ACC) and other regulation hubs go offline. This is why it feels impossible to pause, reorient, to calm down, or to feel present. This overactive self reflection gets stuck in looping in old narratives or catastrophized self-referenced “conspiracy theories” and unable to regulate.

The DMN also works in tension with the Task Positive Network (TPN), which activates when we are engaged, task-focused, and present. Trauma overloads the DMN and silences the TPN, keeping thoughts trapped in the “inner loop” rather than anchored in the now and able to redirect.

EMDR helps rebalance the DMN by interrupting stuck DMN cycles and bringing the ACC and insula back online, allowing for self-awareness, regulation, and the ability to sense the present. Instead of being snatched into shame spirals or dissociation, the DMN can return to its healthy functions: creativity, reflection, and integration.

The Task Positive Network (TPN) is the brain’s “here-and-now network” made up of several regions working together, including the AAC and Insula. It switches on when we are task-focused, present, and actively engaged in goal-directed tasks. EMDR helps shift activation out of the DMN and into the TPN, supporting access to present-moment processing, problem-solving, and flexible attention.

EMDR engages the TPN directly. Bilateral stimulation shifts activation out of DMN loops and into TPN pathways, reawakening the ACC and insula so clients can:

• Notice and regulate body states without overwhelm

• Focus attention long enough to reprocess memories

• Make decisions and access choice in the present moment

• Anchor themselves in safe-enoughness while working on processing difficult memories, emotions, thoughts, and felt states

This is the mechanism that allows traumatic experiences to be processed without the system becoming flooded. The ACC comes back online to guide regulation, the insula reconnects sensation with meaning, and the TPN keeps attention grounded in the here-and-now.

The salience network (SN) is a brain system responsible for coordinating the brain’s resources necessary for determining what is important to pay attention to, both inside the body and outside in the environment.

It includes key nodes such as the Anterior Insula and Dorsal Anterior Cingulate Cortex. This helps the brain respond to changing demands by moderating neural networks.

Trauma skews it toward hypervigilance, resulting in every cue feeling like danger because the salience network sends exaggerated signals to the amygdala and DMN, reinforcing hypervigilance, intrusive memories, or dissociation. This feels like the nervous system being constantly on guard or “waiting for the other shoe to drop.”

EMDR helps rebalance the salience network so the system can detect cues of safety as well as threat, which is key to nervous system recalibration. The salience network learns to tag safety cues as relevant again not just danger as relevant. This shift is critical because it tells the body and brain that connection, regulation, calm, rest, and choice are worth paying attention to in order to exist.

The corpus callosum is the brain’s great neurofiber bridge, connecting the left and right cerebral hemispheres through approximately 200 million to 300 million axons, myelinated nerve fibers.  It allows information to flow between the hemispheres so that thinking, feeling, sensing, and remembering can come together as one coherent experience.

In trauma, this bridge often gets backed up, like a traffic jam at rush hour. Signals pile up in the midbrain and can’t make it across. This is why traumatic memories often feel fragmented, either an overwhelming body flash with no words, or a detached story with no felt connection. The traffic is stuck.

Sometimes the traffic jam is so bad that detours happen, like dissociation, hypervigilance, or numbness. The nervous system finds ways to cope, but the cost is disconnection.

EMDR works like a traffic controller on this highway, ensuring a safer navigation towards a healing destination. Bilateral stimulation signals left-right-left-right, opening the lanes of the corpus callosum and allowing information to cross again. Slowly, the traffic jam clears, lanes reopen, traffic flows, integration happens. Memories can move into long-term storage as part of a coherent life story rather than staying stuck in the present.

This bridge allows the Neocortex to calm the emotional responses of the Limbic System, allowing for the space to make sense of these memories and felt states within a larger life context.