The Asymmetrical Tonic Neck Reflex, commonly known as ATNR, is an involuntary movement pattern present in infants from around 18 weeks in utero. This primitive reflex is a part of normal neurological development and is often referred to as the “fencing reflex” due to the distinctive posture it elicits. When an infant’s head turns to one side, the arm and leg on that same side extend, while the opposite arm and leg flex.
Understanding the ATNR
The ATNR serves several biological functions during early development, playing a role in the birthing process by assisting the baby as it navigates the birth canal. It also helps develop fundamental motor skills, including hand-eye coordination and visual tracking. The reflex contributes to muscle tone development and helps infants learn to reach and explore. It also influences the vestibular system, involved in balance and spatial orientation, laying groundwork for complex movements by promoting early one-sided movements and bilateral integration.
When ATNR Typically Integrates
For typical development, this reflex should naturally integrate, or disappear, as the infant’s nervous system matures. This integration typically occurs between 4 to 7 months of age, though some sources suggest it can persist up to 9 months or even a year in healthy development. Integration means that the automatic, involuntary movements of the ATNR no longer dictate the infant’s limb movements, allowing for more voluntary and controlled actions. This period often coincides with the baby mastering other developmental milestones, such as gaining head control, sitting up, intentionally reaching for objects, and beginning to crawl.
Identifying Signs of Unintegrated ATNR
If the ATNR does not integrate within the typical timeframe, it can interfere with an individual’s motor development and coordination. One common sign of a persistent ATNR is difficulty with crossing the midline, which refers to the imaginary line dividing the body vertically. This can manifest as challenges performing tasks that require the hands or feet to work together across the body’s center, or a preference for using only one side of the body.
Individuals may also exhibit poor hand-eye coordination and visual tracking issues, which can affect reading and writing abilities. Difficulties with balance and overall coordination, including challenges with crawling or an atypical crawling pattern, can also be observed. In older children, signs may include an unusually tight grip on writing tools, an awkward writing angle, or trouble translating thoughts into written text.
Supporting ATNR Integration
When the ATNR persists beyond its expected integration period, various approaches can help support its integration. Encouraging natural movement opportunities can aid integration. Activities that promote movement, such as ample tummy time and carrying infants in different positions, can provide beneficial sensory experiences.
For children where the reflex is still present, developmental movement programs or reflex integration therapies may be considered. These interventions often involve activities designed to mimic early reflex movements, helping to create new neural pathways and encourage independent head and limb movements. Seeking guidance from professionals, such as pediatricians or occupational therapists, is important. These experts can assess the situation and recommend appropriate strategies to support the child’s development and foster the integration of the ATNR.