The Brain Stem, the Vagus Nerve and Primitive Reflexes: Understanding the Foundations of Regulation in Neurodivergent Children

At Brain Development we meet parents of neurodivergent parents all the time. Many of them have found themselves asking the same questions:

• Why does my child struggle to regulate their emotions?

• Why do they go into fight-or-flight over small things?

• Why doesn’t behaviour support alone seem to work?

• Why does my child know what to do, but can’t seem to do it?

For families navigating ADHD, autism, sensory processing difficulties, anxiety or developmental delays, the answers often don’t lie in motivation, discipline or willpower; they lie much deeper, in the foundational wiring of the nervous system. That’s where techniques like brain development therapy can become valuable. 

In order to understand regulation in more depth, we need to start at the root: the brain stem.

The Brain Stem: The Foundation of Regulation and Survival

The brain stem is the first part of the brain to develop. It forms the foundation for survival, safety and regulation, long before higher thinking, language or learning come online.

The brain stem is responsible for:

• Basic survival responses (fight, flight, freeze, shutdown)

• Heart rate and breathing

• Muscle tone and posture

• Sensory filtering

• Arousal and sleep–wake cycles

• Primitive reflexes

• The origin of the vagus nerve

If a child’s brain stem is underdeveloped, overstressed, or poorly integrated, the nervous system may remain in a constant state of defence, even when they’re safe.

This is why many neurodivergent children:

• Appear constantly on edge or overwhelmed

• React explosively or shut down quickly

• Struggle with transitions and unpredictability

• Have difficulty calming once upset

This is not just about behaviour: it is biology.

Primitive Reflexes: Early Brain Stem Patterns That Shape Development

Primitive reflexes are automatic movement patterns controlled by the brain stem. They are present in infancy to support survival and early development and are meant to integrate as the brain matures.

When primitive reflexes (often called retained primitive reflexes) remain active beyond infancy, they can interfere with emotional regulation, movement, attention and emotional control.

Common signs of retained primitive reflexes in children include:

• Poor balance or coordination

• Emotional reactivity or impulsivity

• Sensory sensitivities

• Difficulty sitting still

• Poor posture or muscle tone

• Anxiety or behavioural rigidity

• Challenges with attention and learning

For neurodivergent children, retained reflexes can keep the nervous system “switched on,” making everyday demands feel overwhelming.

Primitive reflexes are not a diagnosis: they are a window into nervous system maturity.

The Vagus Nerve: The Regulator Between Brain and Body

The vagus nerve (often searched online as vagas nerve) is the main communication pathway between the brain stem and the body. It carries information about safety, threat and our internal state.

The vagus nerve influences:

• Emotional regulation

• Stress recovery

• Digestion and gut function

• Heart rate variability

• Social engagement

• Voice, facial expression, and eye contact

When the vagal tone is strong, a child can move in and out of stress and become calm. When vagal tone is low or underactive, the nervous system may remain stuck in survival mode.

As parents you may notice:

• Big emotional reactions

• Difficulty calming after stress

• Meltdowns that seem disproportionate

• Shutdown, withdrawal, or fatigue

• Sensory overload

• Digestive or sleep difficulties

Again, this is not a parenting failure; it is a regulation issue rooted in the nervous system.

How the Brain Stem, Reflexes, and Vagus Nerve Are Connected

These systems do not work in isolation.

• The brain stem houses primitive reflexes and initiates survival responses

• Retained primitive reflexes keep the system in a heightened state of alert

• The vagus nerve reflects whether the body feels safe enough to regulate

If reflexes remain active and the brain stem is overloaded, the vagus nerve cannot do its job effectively. The result is a child who appears “dysregulated,” even when all the right strategies are being used.

This is why top-down approaches alone (reward charts, consequences, talking it through) often fail — the foundation isn’t ready yet.

Supporting Regulation From the Bottom Up

Supporting neurodivergent children means addressing the foundational systems first, not fighting behaviours at the surface.

A bottom-up neurodevelopmental approach may include:

• Supporting brain stem maturity

• Integrating retained primitive reflexes

• Gentle sensory input to improve regulation

• Movement, balance, and postural support

• Supporting vagal tone through safe, rhythmic input

• Reducing nervous system overload before adding cognitive demands

When the nervous system feels safer, regulation becomes possible.

Remember:

Your child is not difficult.They are not choosing chaos.They are not failing to try.

Their nervous system is asking for support at a foundational level.

When we support the brain stem, the vagus nerve and reflex integration, we are not “fixing” a child: we are giving their nervous system the conditions it needs to develop and regulate.

That’s exactly what we aim to do on our child development programmes at Brain Development. 

And from that place, learning, behaviour, emotional growth and connection can finally follow.