What Are Triggers?
A trigger is anything—a sound, smell, image, tone of voice, situation, or sensation—that activates a traumatic memory or stress response in the body. When triggered, we suddenly find ourselves experiencing intense emotions, physical sensations, or behaviors that seem disproportionate to the present moment. Our heart races, our throat tightens, we feel an overwhelming urge to flee or fight, or we shut down completely. The intensity of our reaction doesn't match what's actually happening now because we're not truly responding to now—we're responding to then.
What makes triggers so confusing and distressing is that they often happen instantaneously, bypassing our conscious awareness. One moment we're fine, and the next we're flooded with anxiety, rage, shame, or numbness. We might not even understand why. A colleague's tone of voice sends us spiraling. A certain facial expression makes us want to disappear. A particular smell triggers panic. The reaction arrives before we can think about it, before we can talk ourselves down, before we can remind ourselves that we're safe.
This isn't a failure of willpower or emotional control. It's not weakness or overreaction. Understanding triggers requires understanding how our brain is structured.
The key lies in what's called the "triune brain"—a model that helps us understand why we react before we can think, and why sometimes thinking doesn't help at all.
The Triune Brain: Three Brains in One
The triune brain model, developed by neuroscientist Paul MacLean, describes the human brain as having three distinct parts that evolved at different times and serve different functions. While modern neuroscience has refined this model, it remains a powerful framework for understanding how trauma affects us. These three parts are: the reptilian brain (brainstem), the mammalian brain (limbic system), and the human brain (neocortex). Each operates with different priorities, different speeds, and different relationships to conscious awareness.
Reptilian Brain (Brainstem)
Survival First — Oldest and most primitive
Mammalian Brain (Limbic System)
Emotions & Memory — The alarm system
Human Brain (Neocortex)
Thinking & Reasoning — Newest addition
The Reptilian Brain (Brainstem): Survival First
The oldest and most primitive part of our brain, the reptilian brain or brainstem, is responsible for automatic bodily functions and immediate survival responses. This is where our heart rate, breathing, digestion, and sleep-wake cycles are regulated. It's also the home of our most fundamental survival responses: fight, flight, freeze, and fawn.
The reptilian brain operates entirely outside conscious awareness. It's fast—reacting in milliseconds—and it's binary: safe or unsafe, approach or avoid, act or shut down. It doesn't think, doesn't analyze, doesn't consider options. It simply reacts based on past programming. When this part of your brain detects danger, real or perceived, it initiates the stress response before you even know what's happening.
This is the part of your brain that makes you jump at a loud noise before you realize it was just a car backfiring. It's what pulls your hand away from a hot stove before you consciously register pain. And when you've experienced trauma, it's what gets activated by triggers, throwing your entire system into survival mode in situations that your thinking brain knows are safe.
The Mammalian Brain (Limbic System): Emotions and Memory
The limbic system, which evolved later, is the seat of emotion, motivation, and memory formation. Key structures here include the amygdala (our threat detector and emotional alarm system) and the hippocampus (which processes and stores memories, giving them context of time and place).
The Amygdala
Constantly scanning for threats, comparing current experience to past danger. Operates on "better safe than sorry"—sounds the alarm before you can consciously process what's happening.
The Hippocampus
Marks memories with context—when, where, and "this is in the past." When impaired by trauma, memories get stored without context, making triggers feel like now, not then.
The hippocampus is crucial for understanding triggers because it's responsible for marking memories with context—the when, where, and "this is in the past" information. When trauma occurs, especially repeated or intense trauma, the hippocampus can become impaired or overwhelmed. Memories get stored without proper context, which is why triggered responses feel like the trauma is happening now rather than being safely in the past. Your body can't tell the difference between remembering a threat and experiencing one.
The limbic system is faster than conscious thought but slower than the reptilian brain. It operates largely below conscious awareness, though its effects—our emotions—certainly reach consciousness. When you feel an emotion, the limbic system has already been activated and made its assessment.
The Human Brain (Neocortex): Thinking and Reasoning
The neocortex, especially the prefrontal cortex, is the newest evolutionary addition and what we typically think of as our "thinking brain." This is where language, abstract reasoning, planning, decision-making, and self-awareness happen. It's what allows you to read these words, analyze your experience, understand concepts, and make deliberate choices.
The neocortex is sophisticated, flexible, and capable of complex thought. It can consider multiple perspectives, weigh options, imagine futures, and learn from mistakes. It's where we construct narratives about our experiences, develop insight, and make meaning. When we're regulated and within our window of tolerance, the prefrontal cortex stays online and helps modulate the more reactive parts of our brain.
The Critical Limitation
The neocortex is slow compared to the other two brains, and it requires significant energy to operate. It's also the first to go offline under stress. When survival responses activate, blood flow gets redirected away from the prefrontal cortex. This is why when you're triggered, you can't think clearly, can't access logic, can't remember the coping strategies you learned. Your thinking brain has literally been taken offline.
How Triggers Bypass the Thinking Brain
Understanding the sequence of brain activation helps explain why triggers are so powerful and why we can't simply think our way out of them. When you encounter a trigger, here's what happens in your brain, all within fractions of a second:
The Reptilian Brain Detects
Your brainstem monitors through "neuroception"—unconscious threat detection. When something matches a past danger pattern, it instantly activates the survival response. No analysis, just reaction.
The Limbic System Amplifies
The amygdala fires, flooding you with the emotions connected to the original event. Fear, rage, shame, terror. Without hippocampal context, it's as if the past is happening now.
The Neocortex Goes Offline
Blood and resources redirect away from thinking to survival. You lose access to logic, perspective, language, and the ability to remember "this isn't then." The part that knows you're safe can't help.
This entire cascade happens before your conscious mind catches up. By the time you're aware something has happened, you're already in survival mode. This is why "just calm down" or "think rationally" don't work—the brain structure responsible for thinking rationally has been temporarily taken offline.
Working with All Three Brains: A Somatic Approach
Effective healing from triggers and trauma requires engaging all three levels of the brain—not just the neocortex. This is why purely cognitive approaches often fall short: they're working with the slowest, most vulnerable part of the system while leaving the faster, more powerful parts unchanged.
Brainstem Level
Grounding, breath work, movement, orienting to safety cues
Limbic Level
Processing emotions, updating memory context, resourcing
Neocortex Level
Understanding, meaning-making, new narratives
Somatic therapy works "bottom-up," engaging the body (reptilian brain) and emotions (limbic system) before or alongside cognitive work (neocortex). This approach recognizes that the body holds traumatic memory and that healing happens through felt experience, not just insight.
When we learn to recognize our triggered states with compassion rather than judgment, we can begin to interrupt the cycle. Not by suppressing or controlling, but by providing the nervous system with new experiences—experiences of safety, completion, and regulation. Over time, triggers lose their power as the nervous system updates its threat assessment, finally recognizing that the danger is truly past.