Asymmetrical Tonic Neck Reflex (ATNR)
The ATNR begins about eighteen weeks after conception. It should be fully present at birth and appears to assist the baby’s active participation in the birthing process.
If a newborn’s head is turned to one side, the arm and leg on the side to which the head is turned straighten outward while the opposite arm and leg pull in. The reflex continues after birth and plays an important part in the development of hand-eye co-ordination, object and distance perception.
While the ATNR is operating, the hand moves in conjunction with the head. This connection between touch and vision helps to establish distance perception and hand eye co-ordination. Normally this is accomplished by the middle of the first year of life rendering the reflex unnecessary, closely ensued by its integration. If the reflex persists, the hand-eye connection makes co-ordinated crawling difficult. When walking, turning the head results in the straightening of the arm and leg on the same side, upsetting balance and the normal walking pattern.
Once the hand-eye relationship is established in the early months, the ATNR functions to fix vision on anything that catches their interest. This enforces distance perception. If the ATNR is inappropriately retained the child (adult) is easily distracted by anything that attracts their attention.
With the ATNR retained, tasks involving both left and right sides of the body may be difficult to perform. This includes ears and eyes, as well as limbs, and can therefore make dominance of a side, in regards to that of an eye or hand, hard to distinguish. Turning the head may cause a visual image to momentarily disappear or parts of the visual field to be missed. Visual tracking and judgement of distance may be affected.
Each time the head turns to face the shoulder, the arm is urged to rise and the fingers are queued to open. Writing therefore requires enormous effort to keep the hand on the paper. Furthermore, the subtle movements of the hand required for writing is made even trickier when the head is moved from looking to the blackboard and then back to the hand. Excessive writing pressure to accommodate for this is often used with or without a clenched fist pencil grip. Needless to say, the quality and quantity of writing is affected. The act of writing requires immense concentration often to the extent of compromising thought processing for what is being written. Those natural story tellers who are wonderful with fluency of speech, can be unable to express ideas in written form and are likely to have the ATNR retained.
It has been found clinically that in those with a retained ATNR, looking at a hand will cause neurological disorganisation and body weakness. That is, both body and mind become ‘scrambled’ when the eyes are looking at a hand. This further affects hand-eye processing such as that used with writing, drawing & catching balls.
Adult sportspersons who suffer recurrent shoulder injury often have a retained ATNR. As their hand and eye are not functioning independently, there is a constant stress interrupting the fine balance required for smooth head, eye, arm, and hand co-ordination which may lead to structural problems, thus reducing sports performance.