What is Asymmetrical Tonic Neck Reflex (ATNR)? How the Brain and Body Learn to Work Together
- neurosutton
- Jun 13, 2025
- 5 min read
Updated: Jul 25, 2025
How to Share This with Other Parents aka TL;DR
"The asymmetrical tonic neck reflex (ATNR) is a natural reflex babies have that helps them develop coordination by connecting head movements with the positions of their arms and legs. For kids with Down syndrome, this reflex tends to stick around longer due to slower development in the brain and spinal cord, which can impact their motor skills and posture. Early intervention and therapy is key in helping kids with Down syndrome integrate the reflex, leading to improved movement and learning."
We have a phenomenal OT helping us through Early Intervention. She knows I'm a brain nerd and want to learn... everything. So she'll slip in technical terms and point out what she's observing. Asymmetrical Tonic Neck Reflex (ATNR) was a recent one. When she said it was a reflex, I thought, "No big deal. Reflexes are innate, so we probably don't need to make too much of it." Ha - I was wrong. Digging into multiple sites and papers related to ATNR quickly helped me understand that the ATNR is one of two super important reflexes for survival initially (Moro being the other). The ATNR must be "integrated," or suppressed, to allow psychomotor, social, educational, and communication development to progress (Arcilla, 2023). Yipes, I guess it's a bigger deal than I thought.
Vestibular Nuclei: The Brain’s Balance Center
When a baby turns their head, the vestibular system, the inner ear’s balance mechanism or neural GPS for spatial orientation, sends signals to the vestibular nuclei deep in the brainstem. These nuclei act as the body’s internal compass, helping your child orient themselves in space. For the asymmetrical tonic neck reflex (ATNR), they trigger a predictable pattern: the arm and leg on the same side as the gaze extend, while limbs on the away from the gaze flex. This reflex helps babies start to map out where their body parts are, laying groundwork for later skills like reaching and rolling.
In Down syndrome, vestibular processing delays can sometimes leading to a longer-lasting ATNR. A “retained ATNR” can make it harder for children to develop steady balance and coordinated movements.
Spinal Interneurons: The Reflex Connectors
Within the spinal cord, specialized neurons called interneurons act as traffic controllers, relaying and refining the messages between the brain and muscles. When the head turns, these interneurons coordinate the extension and flexion of limbs, ensuring the ATNR happens smoothly. If these spinal circuits are slow to mature or disrupted, the reflex may linger, making posture and movement more challenging.
The nitty-gritty, glorious details
GABAergic/glycinergic interneurons presynaptically inhibit proprioceptive signals, refining the reflex’s precision (Stachowski, 2021).
Satb2 interneurons (laminae V–VI) integrate proprioceptive and nociceptive input, coordinating limb flexion/extension during head turns (Stachowski, 2021). Neurodevelopmental delays can arise when these interneurons consistently misfire, resulting in an ATNR that persists and may manifest as jerky eye movements or asymmetrical posture.
Motor Cortex and Corticospinal Tract: Overriding the Reflex and Gaining Voluntary Control
As babies grow, the motor cortex, which is the brain’s movement command center, begins to assert control. Signals travel down the corticospinal tract, a bundle of nerve fibers that connect the cortex to the spinal cord (including the Satb2 interneurons; Kalambogias, 2021). This pathway gradually overrides primitive reflexes like the ATNR, allowing for purposeful, voluntary movements such as reaching, grasping, and eventually crawling.
The process of gaining voluntary control via the motor cortex is called integration. Typically, the reflex integrates between three and nine months, but optimally by six months.
For children with Down syndrome, integration can be delayed. Myelination takes longer to develop and is not as thick for those with Down syndrome (Olmos-Serrano, 2016 – Cool paper that we will revisit!). The practical implication is that signals from the brain take longer to get to the brainstem and spinal cord to “quiet” the reflex. Slower development of myelination equals a longer window to integrate the reflex. Similarly, if the domino of integrating the ATNR is slow to fall, the next program in development starts later or may begin a little out of sync… which is why early intervention is so important.
Why Integration Matters
If the ATNR persists beyond the first six months, it can interfere with important skills in school-age and beyond:
Motor development: Rolling, crawling, handwriting, and sports
Posture: Asymmetrical muscle tone may contribute to spinal issues like scoliosis.
Attention and learning: The ongoing reflex can compete with the brain’s ability to focus and organize new information.
Therapeutic Pathways
Research shows that targeted therapies can help children with Down syndrome integrate the ATNR more effectively (Adams, 2020). These interventions use gentle movements and sensory input to strengthen the connections between the vestibular system, spinal interneurons, and the developing motor cortex. Early intervention is key. With the right support, these amazingly resilient children can build the neurological foundation needed for more complex skills.
Conclusion
Who knew that a “simple” reflex was so important and so interesting? Every small step, reach, and roll helps our kids’ brains and bodies learn to work together in new ways. So thankful to be able to embrace curiosity….
What has this post made you curious about? Drop a comment below!
References
Adams J. MNRI® efficacy in Down syndrome: Reflex integration outcomes in children. Int. J. Neurosci. Rehabil. 27, 112–118 (2020).
Arcilla CK, Vilella RC. Tonic Neck Reflex. [Updated 2023 May 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK559210/
Fetz E.E., Perlmutter S.I. Spinal neurons in movement: The neurophysiology of spinal cord circuits. Curr. Opin. Neurobiol. 10, 699–707 (2000).
Fink A.J.P., Croce K.R., Huang Z.J., Abbott L.F., Jessell T.M., Azim E. Presynaptic inhibition of spinal sensory feedback ensures smooth movement. Nature. 509, 43–48 (2014).
Harkla. Asymmetrical tonic neck reflex: What is it and why is it important?. Harkla Blog. https://harkla.co/blogs/special-needs/asymmetrical-tonic-neck-reflex (2025).
Heloa. Asymmetrical tonic neck reflex: Key stages in child development. Heloa Blog. https://heloa.org/asymmetrical-tonic-neck-reflex (2025).
Jeanmonod D., Magnin M., Morel A. Low-threshold calcium spike bursts in the human thalamus: Common physiopathology for sensory, motor and limbic positive symptoms. Brain. 119, 363–375 (1996).
Kalambogias J, Yoshida Y. Converging integration between ascending proprioceptive inputs and the corticospinal tract motor circuit underlying skilled movement control. Curr Opin Physiol. 2021 Feb;19:187-193. doi: 10.1016/j.cophys.2020.10.007. Epub 2020 Nov 13. PMID: 33718693; PMCID: PMC7949357.
Olmos-Serrano JL, Kang HJ, Tyler WA, Silbereis JC, Cheng F, Zhu Y, Pletikos M, Jankovic-Rapan L, Cramer NP, Galdzicki Z, Goodliffe J, Peters A, Sethares C, Delalle I, Golden JA, Haydar TF, Sestan N. Down Syndrome Developmental Brain Transcriptome Reveals Defective Oligodendrocyte Differentiation and Myelination. Neuron. 2016 Mar 16;89(6):1208-1222. doi: 10.1016/j.neuron.2016.01.042. Epub 2016 Feb 25. PMID: 26924435; PMCID: PMC4795969.
Physiopedia. Asymmetrical tonic neck reflex. Physiopedia. https://www.physio-pedia.com/Asymmetrical_Tonic_Neck_Reflex (2025).
Stachowski NJ, Dougherty KJ. Spinal Inhibitory Interneurons: Gatekeepers of Sensorimotor Pathways. Int J Mol Sci. 2021 Mar 6;22(5):2667. doi: 10.3390/ijms22052667. PMID: 33800863; PMCID: PMC7961554.
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