Primitive Reflexes in Clinical Practice: Autonomic Dysregulation, Fascial Bracing, and Developmental Retention

Primitive reflexes (PRs) are involuntary motor responses that establish foundational postural tone, orientation, and motor-sensory coordination during early development. These reflexes should integrate as higher cortical control matures. When they remain active—or reactivate in the context of trauma, emotional stress, neuroinflammation, or structural compromise—they produce persistent motor patterns that disrupt movement, stability, and autonomic regulation.

In clinical settings, retained PRs do not present abstractly. They express through specific, reproducible fascial bracing patterns, muscle spasticity, and sinew channel fixation. These patterns impair functional mobility, destabilize postural tone, and often correlate with elevated sympathetic drive, reduced vagal tone, and impaired cranial nerve regulation.

The Unintegrated Body: Autonomic Dysregulation and Subclinical Adrenal Dysfunction

This model proposes an integrated framework for understanding the pathomechanisms of subclinical adrenal dysfunction, connecting deep physiological drivers to downstream clinical expressions. It serves as a working theory for practitioners who observe localized, non-systemic patterns of circadian dysrhythmia and persistent sympathetic dominance in their clients. This model demonstrates how a fundamental distortion in the balance of the nervous system can create a cascading series of effects, from cellular processes to the observable symptoms that manifest in the body. The simultaneous development of the sinew channels, the autonomic nervous system (ANS), the enteric nervous system (ENS), the limbic system, and the vestibule is why therapeutic work on the sinew channels can effect change across multiple systems. Because these signs of dysautonomia are visibly and objectively reflected in the fascial and sinew channel patterns, practitioners can learn to recognize the symptoms of localized cortisol inhibition and re-effect systemic balance through targeted interventions.

A Unified Field Theory for Dysautonomia: A Hub and Spoke Model for Navigating Systemic Trauma Recover

This model is designed to be a roadmap. The Hub is the central, unifying cause. The Spokes are the distinct, yet interconnected, systems where the dysfunction manifests.  This is an actual case so none of this is theory.

The Startle Reflex: The Initial Spark of Freeze–Fight–Flight Activation

The Startle Reflex is the earliest postural motor reaction to sudden sensory input, emerging in utero between 9–12 weeks gestation. It serves as a primitive survival mechanism, activating the reticular brainstem in response to unexpected threat—auditory, tactile, vestibular, or visual. Unlike the Moro Reflex, which follows a full arc of extension and recoil, the Startle reflex is a pure flexor response, rapid, involuntary, and globally defensive.

When triggered, the response begins with a bilateral blink, followed by immediate contraction of the neck, shoulders, diaphragm, and deep core. This sequence occurs within 30–50 milliseconds, bypassing cortical processing. It is not a social or communicative reflex—it is pure brainstem defense, marking the first motor imprint of hypervigilance.

The Fear Paralysis Reflex (FPR): The Primordial Freeze Response

 The Fear Paralysis Reflex (FPR) is the earliest-appearing defensive reflex in fetal development, emerging as early as 5–8 weeks gestation. It precedes all motoric fight-or-flight responses and represents the organism's first organized reaction to threat: tonic immobility. This freeze state is characterized by stillness, bradycardia, breath-holding, and muscular tension throughout the deep core.
Unlike the Startle or Moro reflexes, which produce visible motor output, FPR is a silent, full-body inhibition. Its role is to make the fetus "invisible" in response to intrauterine or environmental threat—predator, vibration, or maternal stress. It is autonomic, vagal-dominant, and deeply subcortical, involving cranial and sacral parasympathetic regulation.

The Moro Reflex: The Core Disruptor of Gut–Brain–Body Integration

The Moro Reflex, distinct from the simpler Startle Reflex, is a higher-order primitive reflex that appears at birth and is typically integrated by 4–6 months of age. It is triggered by a sudden loss of support—as if the infant is falling—and results in a global motor response: the arms and legs shoot outward, hands open wide, then recoil in a grasping motion, often accompanied by crying. This reflex is not a mere startle—it is the first vestibular–sympathetic integration event, combining full-body motor discharge with thoracoabdominal bracing, vocalization, and diaphragmatic lock.

Freeze-Based Reflexes: The Missing Foundation in Primitive Reflex Work

Core Tendon Guard Reflex (CTG): Architectural Overview

Most primitive reflex training programs, particularly those focused on pediatrics, emphasize postural and motor pattern reflexes such as ATNR, STNR, and TLR. Yet many of my early classes omitted the most foundational layer of the reflex hierarchy: the freeze responses.

Startle, Fear Paralysis Reflex (FPR), and Core Tendon Guard Reflex (CTG) all precede the Moro reflex—not just in development, but in function. These are the body’s last line of defense against threat. I first encountered this tier of reflexes through Masgutova’s Neurosensorimotor Reflex Integration (MNRI) work for PTSD. While most pediatric and OT-based programs I have taken did not cover the freeze responses, Masgutova’s system explicitly maps them in the context of trauma and autonomic dysregulation. Dr. Karen Pryor’s neuroplasticity training also explored these reflexes in detail.

Head Righting Reflex

Head Righting Reflexes are a set of midbrain-driven postural responses that begin emerging around 2–3 months of age and remain active throughout life, albeit in a more refined and voluntary form. These reflexes govern the body’s ability to maintain head and eye alignment with the horizon—a prerequisite for balance, coordinated movement, and autonomic regulation.

They are not primitive reflexes in the traditional sense, but rather transitional postural reflexes that replace primitive patterns like TLR, ATNR, and STNR. Their presence indicates maturation of vestibular–ocular–spinal coordination and the emergence of cortical control over postural tone.  

In the last two decades—especially since COVID—we’ve seen a dramatic rise in retained Head Righting reflexes in teens and young adults. Most present with fascial rigidity from T3 upward, compromising cervical rotation, vagal tone, and in severe cases, carotid and sympathetic ganglia function. 

Tonic Labyrinthine Reflex (TLR): Foundational Flexion–Extension Drive and Gravitational Orientation

The Tonic Labyrinthine Reflex (TLR) is one of the earliest reflexes to appear in human development, emerging in utero and typically integrating by 4–6 months of age, though postural traces often persist in clients with dysregulation. It establishes the infant’s first global response to gravitational orientation, mediated not by surface contact but by vestibular input from the otolith system, which senses head position in space. When the infant’s head tilts

forward (into flexion), the body reflexively moves into total flexion; when the head tilts backward (into extension), the body extends. These total-body tone shifts form the first flexor–extensor map across the fascial and muscular systems, organizing anterior–posterior tone in both prone and supine positions.

Landau Reflex: The Postural Bridge Between Core Extension and Spatial Autonomy

The Landau Reflex emerges around 3–4 months of age and typically integrates between 12–24 months, depending on trunk tone maturity and the resolution of earlier primitive reflexes. It appears only after foundational flexor patterns—particularly the Tonic Labyrinthine Reflex (TLR), Asymmetrical Tonic Neck Reflex (ATNR), and residual Moro activity—have begun to recede. This staged emergence reflects the infant’s growing ability to sustain antigravity postural extension.