Ayres (1972) proposes that the continued presence of residual or poorly integrated primitive postural reflexes interferes with the development of postural mechanisms and is a contributing factor to various specific learning disabilities.
“While normally overtly present in the very young infant, maturational processes should gradually incorporate the reflexes into the sensory motor system so they do not interfere with further maturation of the postural mechanisms.” (Ayres 1972 page 98)
Ayres' describes tests for two primitive reflexes: the tonic labyrinthine reflexes (TLR) and the asymmetrical tonic neck reflex (ATNR).
The tonic labyrinthine reflex (TLR)
The TLR is a function of the vestibular system and manifests itself as increased flexor tone in the extremities when in the prone position, and increased extensor tone in the supine position. The result of this proprioceptive facilitation is difficulty raising the head, shoulder and legs up against the gravitational pull.” (Ayres 1972 page 58.) The TLR is tested in prone and in supine.
TLR in prone
In prone the child is instructed to raise the child is instructed to raise the the head, shoulder girdle and legs up off the floor and hold the position while counting aloud to 30.
Ayres' (and other proponents of the retained primitive reflexes) claim that failure on this test is a an indication of a retained TLR. They do not provide any evidence to back up this claim.
An alternative explanation
The ability to maintain this position requires not only good strength in the neck,shoulder, trunk and hip muscles, but also a good flexibility in the trunk and hips.
- The shoulders are in full lateral rotation, a movement that is often limited in children with movement difficulties.
- The ability to maintain shoulder abduction and extension with lateral rotation against gravity requires strong shoulder and scapula muscles.
- Maintaining extension of the thoracic and lumbar spine against gravity requires good strength in the spinal extensor muscles.
- Hip extension with the hip in 0 degrees of abduction requires adequate strength in the hip muscles as well as flexibility.
Children with movement difficulties often have restricted extension of the hips well as restricted mobility of the anterior fascial system that crosses from the anterior pelvic region over the anterior aspect of the hips and thighs.
This restriction can be tested by asking the child to lie in supine with the thighs parallel and then to bend th knees. Children with good flexibility can do this easily.
However, if there is any limitation extensibility in the hip muscle the child will tend to abduct and flex the hips.
Mobilization of the anterior fascial system, including the neurovascular bundle that supports the femoral nerve will often lead to an immediate improvement in the ability to maintain the prone position.
In addition children who tend to sit with a flexed may have poor thoracic extensor muscle strength and also find holding the head in extension difficult and uncomfortable.
Try the following
The strength and flexibility needed to maintain this position for 30s can easily be demonstrated by doing the test. Easy or difficult? Most adults, unless they are fit and flexible will have some difficulty assuming and maintaining the position. Does this mean that most adults have a retained TLR or maybe that they should think about improving their fitness?
Test of the TLR in supine
Ayres (1972) proposed that this reflex be tested by asking a child to curl up by lifting the head, trunk and lower extremities without clsping the arms around the knees. Failure to achieve this position is seen as an indication of the continued influence of the TNR
As with the prone pivot position, the ability to maintain this position depends first and foremost on the strength of the neck and trunk flexor muscles.
The strength of the neck flexors can be tested by asking the child to lie in supine and lift the head, bringing the chin to the sternal notch. Children with movement difficulties have difficulty holding this position and may complain about pain in the neck.
Children who sit in a slumped position often develop tightness in the neck extensor muscles and experience pain with passive flexion of the upper cervical spine.
Asymmetrical tonic neck reflex
In very young infants when lying quietly to head tends to be turned to one or other side. The rotated position is sometimes associated with extending the elbow on the side to which the face is turned, with flexion of the elbow of the other arm. The is often referred to as the fencing position. This tendency is strongest in the infants between 6-8 weeks. However, as the infant learns to hold the head steady in the midline, and also learn to turn the head to the side to look at and follow interesting objects or events the link between turning the head and position of the arms decreases and is not observed in older infants.
Proponents of retained primitive reflexes claim that that this tendency can be seen in children with movement coordination and learning difficulties when they are instructed to stand on hands and knees and turn the head to one side.
The test is said to be positive if the child bends the elbow on the opposite side.
Children with movement difficulties often have tightness in the muscles that join the scapula to the humerus. This tightness can be seen if you test lateral rotation of the shoulder with the shoulder in 90 degrees of flexion and bilateral shoulder adduction. These movements should be easy to perform. (See Shoulder control fro drawing and handwriting)
A look at the close connection between the muscles of the back give insight into way in which lack of extensibility in a muscle group will affect range of movement of the shoulder and the neck.
This tightness affects the normal scapular-humeral rhythm and means that the scapula is a position of protraction/lateral rotation when the arm is positioned at forwards and at right angles to the trunk (flexion to 90 degrees).
Now when the head is turned to one side, say the right, the shoulder girdle is rotated back on right weight is shifted onto the left arm making it more difficult to keep the elbow extended.
Try the following
- Stand on your hands and knees, with the your hips and knees flexed to 90 degree and the hands directly under the shoulders.
- Turn your head rapidly from side to side, turning as far as you can go each time.
- Notice how you shift your weight from side to side and slightly flex the elbow of one arm.
Interestingly, if you tuck your toes in and lift your knees (which shifts more weight onto the arms) and repeat the rapid turning of the head you may notice less of a tendency to flex the elbow. This is because maintaining this position requires stronger muscle work to maintain the position and is thus a little more stable.
|The retained primitive reflexes fallacy
There are three arguments to support the contention that retained primitive reflexes underlies motor coordination difficulties experienced by some children.
1 Proponents of the retained primitive reflex theories base their arguments on reflex and maturational accounts of motor development that were developed in the first half of the 20th century. These theories have been replaced by accounts that stress the embodied and dynamic nature of development, a perceptul-motor understanding of motor control, and the idea that talthough maturation play a role, brain development depends on experience. (See Bibliography)
2 There is no direct evidence that retained primitive reflexes is the underlying cause of movement and specific learning difficulties experienced by some children
3 Tests for retained primitive reflexes are not valid measures
In order to be valid, a test needs to assess what it purports to assess and no other explanation provides an explanation for the outcome. (See Reliability and Validity of Measurement)
The commonly used test used to diagnose retained tonic labyrinthine reflexes require very good strength and flexibility. This means that failing these tests cannot be ascribed to retained primitive reflexes as they are first and foremost test of strength and flexibility.
The same argument can be made for the ATNR test. Turning the head when standing on hands and knees requires good coordination, shoulder strength and flexibility and full range of neck flexion.
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Ayres, A. J. (1972). Sensory integration and learning disorders. Los Angeles: Western Psychological Services.
Bartlett D. Primitive reflexes and early motor development. J Dev Behav Pediatr. 1997 Jun;18(3):151-7.
Corbetta D, DiMercurio A, Wiener RF, Connell JP, Clark M. (2018) How Perception and Action Fosters Exploration and Selection in Infant Skill Acquisition. Adv Child Dev Behav.55:1-29.
Hughes, J. E., & Riley, A. (1981). Basic gross motor assessment. Physical Therapy, 61, 503-511
von Hofsten C, Rosander K. The Development of Sensorimotor Intelligence in Infants. Adv Child Dev Behav. 2018;55:73-106.
Yamada, Y., Kanazawa, H., Iwasaki, S., Tsukahara, Y., Iwata, O., Yamada, S., & Kuniyoshi, Y. (2016). An Embodied Brain Model of the Human Foetus. Scientific reports, 6, 27893.
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