As noted in Part I of this post, in The Body Keeps the Score, van der Kolk describes trauma as a whole-body, whole-mind experience resulting in a profound disruption, overwhelming a person’s coping capacity and leaving lasting imprints on brain and body’s physiological systems. He frames trauma as the result of an individual experiencing significant and often sustained threat that is so frightening, shocking, or violating that it exceeds the individual’s ability to process or integrate the experience(s).
These traumatic experiences lead to a mind-body disconnection wherein the thinking mind may try to bury or minimize the memory, while the body “remembers” through storing the raw sensations, emotions, and survival responses which remain active long after the immediate threat or threats have passed. The experience of trauma leaves a physiological imprint that reshapes an individual’s brain and nervous system, altering how they perceive safety, process emotion, and relate to others. Traumatic experiences that are, perhaps long passed, maintain the body in a persistent physiologically reactive state, triggering anxiety, emotional numbing, rage, or shutdown. This occurs even if conscious recall of the traumatic event(s) is absent. Survivors of trauma often feel a loss of self-ownership, alienated from their own bodies and emotions, as if they have lost control over their inner life.
Below is a brief description of the neurological and physiological systems impacted by trauma inducing experiences.
Neurological Systems
Limbic System (especially the amygdala and hippocampus)
Amygdala: hyperactivation → constant threat detection
Hippocampus: impaired integration of memory → fragmented, sensory-laden recall. The key takeaway here is that trauma can lock the brain into a perpetual state of “threat,” with memories stored as raw sensations rather than as coherent narratives.
Prefrontal Cortex (especially medial prefrontal and anterior cingulate): Among its major functions is the regulation of emotions, impulse control, and self-awareness. Trauma reduces the capacity of prefrontal cortex’s overall activity, weakening the cognitive ability to calm the amygdala and to distinguish past from present danger. Trauma reduces, but does not permanently eliminate, the prefrontal cortex’s ability to calm the amygdala and to differentiate past from present danger.
Brainstem & Midbrain: These areas govern the primitive instinctive reflexes of fight, flight, or freeze that remain in the old reptilian part of the human brain. Trauma can over-engage these automatic primitive survival responses, bypassing higher reasoning capacity of the prefrontal cortex.
Physiological Systems
Autonomic Nervous System (ANS): The ANS is hierarchical. Trauma’s effect on the Sympathetic branch to mobilize energy and create a state of hyperarousal (fight/flight); The Parasympathetic branch is associated with states of calm and relaxation but is also capable under conditions of extreme threat of shutdown and dissociation (freeze). Trauma survivors often oscillate between hypervigilance and numbed collapse.
Hypothalamic–Pituitary–Adrenal (HPA) Axis: The HPA axis regulates the major stress hormones of cortisol and adrenaline. Trauma creates chronic dysregulation in the normal functioning of the HPA system leading to either excessive production and release of the stress hormones release or a blunted response, both of which is harmful to health.
Vagal System: The vagus nerve (ie., the tenth cranial nerve) is the longest nerve in the body. It innervates organ systems throughout the body. It regulates how the ANS, sympathetic and parasympathetic divisions, in turn impact our physiological response to safety and threat. The vagus nerve plays a key role in parasympathetic regulation and has two functionally distinct branches: 1) Ventral vagal (myelinated) which supports calm states and social connection and 2) dorsal vagal (unmyelinated and more primitive) supports immobilization. The Ventral side of the vagus nerve is myelinated in all mammals and supports states of calm (rest and digest) our sense of safety, social engagement, and communication. Strengthening ventral vagal tone (e.g., through breathwork, yoga, and safe relationships) can restore normative physiological regulation in individuals who have been traumatized. Under conditions of extreme threat, the dorsal side of the vagus nerve (unmyelinated and, from an evolutionary perspective, part of an older and more primitive system) is triggered and leads to immobilization and shutdown responses, that result in behavioral freeze, dissociation, collapse and potentially death. Whereas the sympathetic division of the ANS mobilizes energy for fight-or-flight, hyperarousal and anxiety under conditions of danger or threat, overwhelming potentially life-threatening threat activates the dorsal side of the vagus nerve and the individual becomes immobilized.
Immune & Endocrine Systems: The stress hormones, adrenaline and cortisol, are released under immediate threat and designed to be short-lived and beneficial, dissipating when the immediate threat has been eliminated or passed. Chronic production of the stress hormones which occurs under the types of prolonged and sustained threat that results in trauma, impairs immune system functioning and disrupts hormonal balance. This links both chronic stress and trauma to the potential for long-term physical illnesses.
Musculoskeletal & Sensory Systems: Trauma increases the presence of long-term muscle tension, an easily triggered startle reflex, and sensory hypersensitivity. The body “remembers” trauma through posture, movement patterns, and visceral sensations.
Neuroception Guides State Shifts: The subcortical nervous system, continuously and subconsciously scans for cues of safety, danger, or life threat. Neurological, HPA axis, Vagal and musculoskeletal system reactions occur before conscious awareness, shaping both perception and behavior.
Integration in Healing: Van der Kolk’s work stresses that recovery from trauma inducing experiences requires bottom-up (body-based) as well as top-down (cognitive) approaches:
Bottom-up: yoga, breathwork, somatic experiencing, psycho drama, movement therapy all designed to calm the ANS, re-establish bodily safety and increase cognitive ability to calm the amygdala and to distinguish past from present danger.
Top-down: talk therapy (e.g., CBT and Existential Analytic), and neurofeedback intended to reintegrate traumatic memories and restore prefrontal regulation.