Postural reflexes

Postural reflexes are responsible for the subconscious maintenance of the body’s posture when movement and position is altered and they ensure that the body remains upright and aligned. It is the effects of gravity on the body which triggers their response and so these reflexes do not begin to develop until after the baby is born.

All but one of the postural reflexes arise from/are found in the midbrain. This means they are mediated from a higher centre than the primitive reflexes and so their appearance signifies a maturation of the nervous system. The shift from primitive to postural reflexes is gradual and there will be over-lap whilst both are present but the postural reflexes should be established by the time a child is three and a half. They should remain for life but with age they may decay, allowing the primitive reflexes to re-appear.

The postural reflexes are divided into two groups – the righting reflexes and the equilibrium reactions. The primitive reflexes have formed the foundation for conscious movement and the postural reflexes allow subconscious control of posture, balance and coordination in the active and static individual. They help the baby develop from a passive little mass to an active being who can roll, sit, crawl, stand, walk and run and their contribution leads to an individual who can respond, at every stage, to a loss of balance and weight change in order to maintain body alignment or posture in space.

Once the postural reflexes are fully present and integrated, they will be activated depending on the degree of disturbance to balance. If only the head is misaligned, the righting reflexes will suffice; if the body is threatened to be moved beyond its base, then the equilibrium reactions will necessary.

 

Righting reflexes

The righting reflexes develop after birth and remain for life. They help the body to respond to rapid loss of balance and assist with integrated movements of the head on the trunk. The righting reflexes help take the maturing child through the developmental milestones of head control, rolling, sitting, crawling and standing.

 

Neck righting reflex

The first of the righting reflexes to appear is the neck righting reflex. It is present at birth in a normal full term baby and strongest at about three months of age. It is triggered by stretching of the neck muscles when there is rotation of the head or movement of the cervical/neck spine. With the baby in supine/on his back, if the head is turned to one side, the whole body will follow, in what is called a log roll, until it is brought into alignment with the head.

 

The Labyrinthine Head Righting Reflex (LHRR)

The LHRR is one of the most important of the righting reflexes. It emerges fully at about two months of age and enables the baby to start lifting his head in prone/on his tummy. Head lifting from supine/on his back develops more slowly than the lifting in prone.

Head control is a vital skill and, without it, normal physical development is seriously compromised. A newborn baby has no head control at all. At four weeks, a baby in prone/on his tummy can lift his head for a moment or two. By 12 weeks of age, a baby on his tummy should be able to hold his head up and prop himself up on his forearms. By 24 weeks, his head control is strong and he can hold his weight on extended/straight arms. In supine/on his back, a newborn baby’s head lag (the head hangs backwards when he is pulled to sitting) will be full but gradually this will decrease – by the time he is 12 weeks old there will be a slight lag and at 20 weeks there will be none. At 24 weeks, he will raise his head in anticipation of being pulled up.

The LHRRs are strongest at ten months. They are responsible for maintaining the head in an upright position with eyes facing forward and level with the ears. It is reflex triggered by the position of the otoliths in the labyrinths of the ear (vestibular information) and somatosensory (body sensations) inputs. These set off postural adjustments to restore the head to a normal position as the body moves.

The LHRR operates in both forwards and backwards and side to side directions when the body is upright. If the body moves forwards, the chin lifts and head tilts back and vice versa. If the body tilts to the right, the neck flexes/bends to the left sufficient to keep the eyes horizontal.

 

The Oculo-headrighting Reflex (OHRR)

This reflex is mediated in the cortex and requires intact vision and enough light in which an object can be seen. It will not function with the eyes closed or in the dark.

For our eyes to operate usefully, we need stable head control, especially when the body and head move, and also the ability to fix our gaze and follow an object. The OHRR will maintain the required stability of the head, whilst the body moves, allowing the gaze to remain focused and fixed.

 

The body righting reflex

The body righting reflex is also known as the body-on-body reflex. It appears at about seven months of age and is the response of the body to pressure stimulation. The body will right itself independently of the head, so this reflex modifies the neck righting reflex. It plays a role in helping the child to move from sitting to standing.

 

Segmental rolling reflex

The segmental rolling reflex develops at about six months of age and is a mature adaptation of the neck righting reflex and the body righting reflex. As its name suggests, rather than the body moving as one block, rotation/turning appears to take place about a central axis of the body and the shoulder and pelvis move separately. If the rolling movement starts with head rotation, the shoulders will follow, and then the pelvis. The movement can also be initiated from the opposite direction, at the pelvis.

Rolling usually starts at about six months – supine/on his back to prone/on his tummy will be first and prone to supine a couple of months later. Once these movements are fully mastered, the segmental rolling reflex will not be used for this purpose but will be activated to smooth out movements such as running and jumping later on.

 

The Landau reflex

The Landau reflex is difficult to classify – it is not a primitive reflex because it is not present at birth and it is not a true postural reflex because it should not persist beyond the age of a year. Many class it as a righting reflex but it may best be described as a bridging reflex. It is present from about three months until twelve months of age, although traces may be seen up to three and a half years until full reflex integration has taken place.

When the baby is held in ventral suspension/supported under the tummy, the head, spine and legs will extend and he will ‘fly like an aeroplane’. In prone/on his tummy, the Landau helps with extensor/straightening tone, so it acts as an inhibitor to the TLR in flexion. When the child can lift his head and chest, he is being prepared for movements such as crawling and getting into standing.

If the Landau persists, the child may have retained primitive reflex(es) and poor development of balance. He may have trouble with lower limb movement particularly into flexion; he may run in a stiff and awkward manner and have difficulty jumping and hopping.

 

Equilibrium Reactions

The equilibrium reactions appear at about six months of age and remain for life. Their action is subconscious but, unlike a reflex response, their movement response is event specific and unique to each situation. It is no coincidence that their influence becomes noticeable as a child goes from lying to sitting. A baby has a large body ‘footprint’ in lying but in sitting this is much reduced to a smaller base. Sitting also brings with it greater challenges to balance due to the effects of gravity.

Maintaining balance is a complex process and is dependent on the level of maturity of the nervous system (toddlers are less stable than teenagers), the mobility of joints in the spine and limbs (young adults have an advantage over the elderly) and muscle power. As an infant grows, his central nervous system matures, his muscle power increases and primitive reflex movement gives way to voluntary cognitive movement supported by the righting and equilibrium reactions.

The equilibrium reactions work by affecting either the position of the centre of gravity of the body or by altering the position or size of the base through which balance is to be maintained.

These reactions can be categorised into three groups.

• Moving the base – the reaction makes you move to maintain balance. This means that you step or hop and move your body to keep upright. Depending on the degree of displacement and the force of the displacement, this may be a total body response or a simple skip to maintain balance
• Keeping the centre of gravity over the base. This is done by (a) weight shifting – for example moving the weight to one leg to allow a step to be taken or (b) by moving arms, legs, with torsional/twisting movements of the spine to maintain balance within the base
• Widening the base and lowering the centre of gravity by using the arms in protective extension – such as the parachute reflex (see below) or, for instance, placing your feet further apart to widen your stance

The first two categories above are higher functioning/more mature than the last, as they do not necessarily involve the use of the arms and hands.

Equilibrium reactions are the last of the developmental motor reflexes to mature and their effect on balance allows a multidirectional range of movements to be made so that it is possible to either voluntarily taking the centre of gravity outside the base or efficiently respond to forces that have done so. They are mediated/found in the cortex and are controlled together with the cerebellum to allow fine tuned, responsive and protective movement.

 

The Parachute Reflex

The parachute reflex emerges at about eight months and is the last of the postural reflexes to appear. It is a defensive response and involves the arms being used in protective extension. If the infant is held in suspension and suddenly moved towards the floor, his arms straighten as if to prevent him from falling.

The propping reaction is a similar response with the action being to the side. This can be tested from about seven months in a seated child who is tilted to one side – his arm will extend to protect him from falling to that side.

 

What happens if the postural reflexes are underdeveloped?

The purpose of the postural reflexes is to maintain static and dynamic balance, posture and correct alignment of the head and body. Underdeveloped postural reflexes mean that balance and coordination will be poor. This not only has the obvious effect of lack of protection from falling but has wider implications socially and in the classroom.

The effects of immature postural reflexes are not well documented but will include;

• Poor postural control, body alignment and postural tone
• Poor coordination, bilateral integration and motor control of fine movements
• Weak head control and/or associated head movement
• Compromised gaze control
• Reduced visual-motor/hand eye integration and fixation
• Difficulties with reading and writing
• Inadequate sensory integration
• Gravitational insecurity and increased anxiety
• Problems with adaptation, sequencing, multi-processing, information overload
• Retained or partially integrated primitive reflexes

Righting reflexes and equilibrium reactions are more complicated than the primitive reflexes. Their functions are mediated in more developed, higher areas of the brain. This explains why they appear later, developmentally, as the child grows and the system matures. When a child has underdeveloped postural reflexes, a  stressful situation may set off a ‘lower’ level of response – this may result in a primitive reflex being triggered to respond to the stress. Such a response is inappropriate – it is inefficient, inaccurate and ‘not fit for purpose’ but the immature nervous system has no other way to react.