Trauma – When the Brain "Overheats"
During a traumatic experience, our brain becomes flooded with stress hormones. This adversely affects brain nerve cells, particularly the hippocampus. The communication and coordination between the amygdala and the hippocampus are disrupted. Emotional states, images, and bodily reactions remain stored in the amygdala, while the hippocampus fails to fully link these experiences with external reality.
As a result, what is known as “hippocampal amnesia” occurs—the absence of a clear memory regarding the specific real situation.
If trauma remains unprocessed, the emotional memory of the amygdala's “hot system” dominates over the autobiographical memory of the hippocampus's “cool system.” A stark contrast forms between highly intense memories on one hand and memory gaps concerning specific events on the other. Because these incomplete memories cannot yet be integrated and organized, they begin to live an independent life that largely evades conscious control.
Many stimuli can act as triggers, evoking powerful emotional memories in those affected by trauma.
Key Brain Structures in the Trauma Process
Thalamus: Processes sensory input.
Amygdala: Traumatic memories are “burned into” or deeply engraved in consciousness; unintegrated memories begin to live an independent life.
Hippocampus: The experience fails to connect with reality, resulting in hippocampal amnesia.
Cerebral Cortex: Traumatic events are not stored in memory, or are only partially retained.
Trauma Integration / Processing: For trauma to be processed, the traumatic event must be placed into a broader context. Only then can a healing perspective emerge: “It is over, and I survived it.”
How Trauma Alters the Brain
Trauma can leave deep psychological scars that prevent individuals from living a full and happy life. People who have experienced trauma may face flashbacks, nightmares, sleep disturbances, as well as memory and concentration difficulties. Even the slightest reminder of the event can trigger a frightening re-experiencing of the traumatic event.
Trauma survivors may also experience feelings of guilt, shame, nervousness, exhaustion, as well as emotional numbness or a sense of detachment from others.
Trauma is not something one can simply "get over." For some, the effects last only a few weeks or months, but for others, symptoms can persist for a lifetime, linked to feelings of helplessness, isolation, depression, personality disorders, and addiction.
According to data published in Dialogues in Clinical Neuroscience, at least 8% of Americans have experienced trauma at some point in their lives.
While trauma or PTSD is often associated with warfare, a traumatic experience can be any deeply distressing event, such as:
Car accidents
Natural disasters
Bullying
Relationship breakdowns
Death of a loved one
Severe illness
Sexual assault
Domestic violence
Three Key Structural Changes in the Brain
Researchers have discovered that although trauma affects brain structure and function in numerous ways, three primary areas are most significantly impacted: the hippocampus, the amygdala, and the medial prefrontal cortex.
1. The Hippocampus
The hippocampus is the region responsible for memory. It helps organize new and old memories, determining where in the brain they should be stored so they can be recalled when needed.
Trauma disrupts this process. Traumatized individuals lose the ability to distinguish past memories from present reality; as a result, memory fragments get “stuck” in the hippocampus rather than being properly distributed to other brain regions. Even old memories are experienced as if they are happening now, keeping the brain in a state of constant alarm and causing the person to perceive danger at every turn.
This explains why even a scene in a movie can trigger severe flashbacks for a trauma survivor.
An excessive buildup of stress hormones in the brain can cause the hippocampus to shrink or develop incompletely. However, this damage is not always irreversible.
2. The Amygdala
The amygdala, often called the “fear center,” is an almond-shaped structure located deep within the brain. It is a primitive region that operates on raw emotion and is unconnected to conscious thought or logical reasoning.
Intimating survival, the amygdala triggers the release of stress hormones that activate the "fight-or-flight" response to help escape danger.
Researchers believe trauma renders the amygdala hyperactive, causing individuals to experience immense stress when confronted with stimuli reminiscent of the trauma—even if those stimuli pose no actual threat.
When the amygdala releases excessive stress hormones, stress escalates further, triggering even more hormone release. Consequently, the traumatized person remains in a continuous state of hyperarousal.
While trauma can cause the amygdala to enlarge, these changes—similar to those in the hippocampus—can also be reversed.
3. The Medial Prefrontal Cortex
The medial prefrontal cortex is situated at the front outer section of the brain. It is a highly evolved region responsible for:
Regulating emotions,
Assessing potential threats,
Controlling impulses,
Evaluating appropriate actions.
Unlike the amygdala, this part of the brain is dedicated to rational and reflective thought.
Problems arise when the brain becomes overwhelmed by stress hormones, leaving a traumatized person unable to differentiate between real and perceived danger. Emotional regulation and impulse control become severely impaired.
Healing the Brain
Scientists believe that the damage caused by trauma can be repaired, and the brain can be rewired. However, healing from trauma almost always requires the assistance of experienced therapists or counselors.
Attempts to handle trauma entirely on one's own are rarely successful, and trying to "bury" or ignore the problem usually worsens the situation, as true recovery requires fully feeling and processing painful emotions.
While counseling and medical treatments are often effective, trauma and PTSD are complex conditions with no single universal solution. Some benefit from hypnosis or mindfulness practices, while others find strength in support groups with peers who share similar experiences.
Many also benefit from addiction treatment programs, particularly when alcohol or substances have been used to self-medicate trauma symptoms.
How Our Brain Functions
The brain's primary obligation is to ensure our survival under even the most adverse conditions. Everything else is secondary. To accomplish this, the brain must:
Generate internal signals that register bodily needs (e.g., food, rest, protection, sex, shelter);
Create a map of the world to direct us where to satisfy those needs;
Generate the energy and actions required to get us there;
Warn us of dangers and opportunities along the way;
Adjust our actions according to shifting environmental demands.
Because humans are mammals—creatures that survive and thrive only in groups—these imperatives require coordination and cooperation.
Psychological issues arise when internal signals fail, when our internal maps lead us astray, when we are too paralyzed to move, when our actions misalign with our needs, or when our interpersonal relationships collapse. Every brain structure plays a role in carrying out these core functions, and trauma can disrupt any one of them.
Our rational, cognitive brain is actually the most recent evolutionary addition, occupying only about 30% of our cranial space. The rational brain focuses primarily on the external world—seeking to understand how things and people work, how to accomplish goals, plan time, and sequence actions.
Beneath the rational brain lie two evolutionarily older and somewhat separate brain systems responsible for everything else: they continuously monitor and coordinate bodily physiology, registering comfort, safety, threat, hunger, fatigue, desire, longing, excitement, pleasure, and pain.
The Three Evolutionary Layers of the Brain
The brain develops from the bottom up—layering during embryonic growth much like it did throughout evolution.
1. The Reptilian Brain
The most primitive part, active at birth, is the ancient animal brain—often referred to as the reptilian brain. It resides in the brainstem, just above where the spinal cord enters the skull.
The reptilian brain governs basic infant functions: eating, sleeping, waking, crying, breathing, sensing temperature, hunger, wetness, and pain, as well as eliminating bodily toxins through urination and defecation. The brainstem and the hypothalamus (located directly above it) jointly control the body's energy levels. They coordinate cardiac, pulmonary, endocrine, and immune functions, keeping these essential life-support systems in a stable state of balance known as homeostasis.
Breathing, eating, sleeping, defecating, and urinating are so fundamental that their importance can easily be overlooked when considering complex behavior and cognition. Yet, if sleep is disrupted, gut function fails, chronic hunger persists, or touch triggers a desire to scream (as frequently occurs in traumatized children and adults), the entire organism loses balance. A vast number of psychological issues are rooted in disruptions of sleep, appetite, touch sensitivity, digestion, and arousal. Any effective trauma treatment must address these baseline bodily functions.
2. The Limbic System (Mammalian / Emotional Brain)
Located directly above the reptilian brain is the limbic system, also known as the mammalian brain because it is present in all social animals that nurse their young. Its development accelerates after birth. It serves as the seat of emotions, the threat detector, the judge of what is pleasurable or frightening, and the arbiter of what matters for survival. It is the command center for navigating complex social networks.
The limbic system shapes itself in response to experience, interacting with a child's genetic code and innate temperament. Everything a child experiences helps refine the emotional and perceptual maps created by the developing brain. As Dr. Bruce Perry notes, the brain is organized in a “use-dependent” manner. This reflects neuroplasticity—the principle that neurons that “fire together, wire together.” When neural circuits fire repeatedly, those patterns become default responses. If you feel safe and loved, your brain specializes in exploration, play, and cooperation; if you feel frightened and unwanted, it adapts to manage fear and abandonment.
As infants and young children, we learn about the world through movement, reaching, crawling, and discovering what happens when we cry, smile, or resist. We experiment continuously with our environment—how do different interactions affect how our body feels? These early explorations form the limbic structures responsible for emotion and memory. However, these structures remain vulnerable to significant alterations from later experiences—for better (e.g., close friendships, falling in love) or for worse (e.g., violent assault, severe bullying, or neglect).
Together, the reptilian brain and the limbic system form the “emotional brain.” The emotional brain is the core of the central nervous system, dedicated to your immediate wellbeing. When it detects a threat or a vital opportunity (such as a promising partner), it alerts you by releasing chemical messengers. The resulting visceral sensations (ranging from mild nausea to panic in the chest) interrupt your current focus and physically and mentally redirect your attention. Even in subtle forms, these sensations heavily influence choices throughout life—what we eat, where and with whom we sleep, the music we prefer, our hobbies, who we form friendships with, and whom we distrust.
The cellular organization and biochemistry of the emotional brain are simpler than those of the neocortex (our rational brain), and it evaluates incoming information in broader terms. Consequently, it jumps to conclusions based on rough similarities—unlike the rational brain, which is built to analyze complex choices (e.g., recoiling in fear at a snake before quickly realizing it is just a coiled rope). The emotional brain triggers pre-programmed survival responses, such as "fight-or-flight." These muscular and physiological reactions are automatic, initiating without conscious thought or planning, while rational awareness connects only later—often long after the threat has passed.
3. The Neocortex and Prefrontal Cortex (Rational Brain)
Finally, we reach the outer layer of the brain—the neocortex. While other mammals possess a neocortex, ours is significantly more developed. During the second year of life, the frontal lobes—which make up the majority of the cortex—begin expanding rapidly. Ancient philosophers considered seven to be the “age of reason” for good reason. Early education relies on frontal lobe capabilities: sitting still, controlling sphincters, using words instead of acting out, comprehending abstract symbols, planning for tomorrow, and cooperating with peers and teachers.
The frontal lobes govern the traits that make humans unique in the animal kingdom. They enable language, abstract thought, and the capacity to absorb, integrate, and assign meaning to information. Despite the impressive linguistic feats of chimps and primates, only humans use words and symbols to construct communities, spiritual frameworks, and historical contexts.
The frontal lobes allow us to plan, reflect, imagine, and project future scenarios. They help us anticipate outcomes based on our choices (e.g., applying for a new job versus failing to pay rent). They make choice possible and serve as the foundation for human creativity. Generations of frontal lobe activity, working collaboratively, have built our culture—advancing humanity from dugout canoes to airplanes, hybrid vehicles, and instant global communication.
References & Credits:
This material was prepared and compiled based on the work and insights of leading trauma researcher and psychiatrist Dr. Bessel van der Kolk, M.D., from his internationally acclaimed book, “The Body Keeps the Score: Brain, Mind, and Body in the Healing of Trauma.”