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Primitive reflexes

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A reflex action is essentially an automatic and specific response to a particular stimulus.

Adult humans have many reflexes, but there are some very interesting ones that are specific to them in the first year of life. These reflexes disappear (or are inhibited) later, as the child moves through a normal course of child development. These primitive reflexes are also called infantile reflexes, infant reflexes, or newborn reflexes. [1]

The frontal lobes are responsible for suppressing these primitive reflexes in adults, but the reflexes begin in the brain stem.

Primitive reflexes reappear in adults under certain conditions. Namely, neurological conditions like dementia, traumatic lesions, stroke, etc. [2][3]

Older children and adults with atypical neurology (for instance, people with cerebral palsy) may retain these reflexes. An individual with cerebral palsy and typical intelligence may teach him- or herself to suppress these reflexes, but the reflex might resurface under certain conditions. For instance, a person with cerebral palsy might learn to suppress the Moro reflex under most circumstances, but may experience the reflex when extremely startled. It is also common that an individual with cerebral palsy whose primarily disability is limited leg use might retain Babinski reflexes, while otherwise having typical speech and so forth. In other words, he or she might have motor control of legs that is around a 12-month level while having otherwise typical adult development. Many individuals who use a wheelchair or crutches for mobility have never lost the Babinski reflex. In individuals with hemiplegia, the reflex might be seen in the foot on the affected side only.

When an individual has suspected brain injury, neurologists test the primitive reflexes to identify the location of the lesion because primitive reflexes are suppressed in the frontal lobe. If they are not being suppressed properly they are called frontal release signs.

Atypical primitive reflexes are currently being looked into as potential early warning signs of Autism Spectrum Disorders. [4] There is speculation about a simple tilt test being used to screen for these issues early. [5]

Main article: Startle reflex

Walking/Stepping

Stepping

Walking/Stepping Reflex

The Walking reflex is also present at birth, and it disappears around the same time as the Moro reflex at 2 months. Although children of this age can't support their own weight with their legs, whenever the soles of their feet touch a flat surface you'll see that they will place one foot in front of the other and "walk". This automatic response disappears and then reappears as a voluntary behavior at around a year old. This reflex is also referred to as the stepping reflex.

See Also:

Rooting

Rooting

Rooting Reflex

The Rooting Reflex assists in breastfeeding, and thus is present at birth. It lasts a bit longer than the Moro or Walking/Stepping Reflex and is with a child till around the age of 4 months. It starts out a bit differently than it ends (slowly moving toward voluntary control), which makes it particularly interesting to examine. At first newborn children simply turn their head toward anything that strokes their cheek or mouth. When they are brand new, they will search for whatever touched them by moving their heads in steadily decreasing arcs until the object is found. After the child becomes used to responding in this way, they will get better at it and be able to move directly to the object without a "search". Most breastfed children have moved on to this direct approach by around 3 weeks old.

Sucking

Main article: Sucking reflex

The sucking reflex seems to belong with the Rooting reflex. It is present before birth, and also aids in breastfeeding. It causes the child to instinctively begin to suck on anything that touches the roof of their mouth. This reflex is common to mammals, and specifically designed to express milk through the breastfeeding process. There are two stages to the action.

  1. The first is the expression stage, which is activated when the nipple is placed between a child's lips and touches their palate. They will instinctively press it between their tongue and palate to draw out the milk.
  2. The second phase is the actual milking action, which involves a tongue movement from areola to nipple that coaxes milk from the mother to be swallowed by the child.

Tonic Neck

Tonic

Tonic Neck Reflex

The Tonic Neck Reflex or Asymmetric Tonic Neck Reflex is present at birth and dwindles away around the age of 4 months old. This reflex is sometimes referred to as the fencing posture. If the child's head is turned to the side, the arm on that side will straighten and the opposite arm will bend. Oddly enough, because this reflex is subtle you may not see it very clearly (especially if the child is otherwise occupied with crying). If the child cannot overcome this reflex and move out of this position (or the reflex continues to be triggered after the child is over 6 months old), the child may have an upper motor neuron disorder of some kind.

See Also:

Palmar Grasp

Main article: Palmar grasp reflex
Grasp

Palmar Grasp Reflex

The Palmar Grasp Reflex is a fairly persistent one. It appears at birth and manages to hang around until about the age of 5-6 months. Whenever an object is placed in the child's hand and strokes their palm, they will grasp it. The grip is incredibly strong, but unpredictable. A child may release suddenly or not be able to support their own weight, so you can't depend upon it. If you want the child to release, however, you can often stimulate the hand into opening by stroking the side of the palm or the back of the hand.

See Also:

Plantar Reflex

The Plantar Reflex or Plantar Grasp is present at birth and fades around the first year. An infant's toes will curl up tightly when something rubs against the ball of their foot.

Babinski Reflex

Babinski

Babinski Reflex

This is a reflex that is often confused with the Plantar Grasp. It is also present at birth, and fades around the first year. If you stroke the side of a child's foot, their toes will fan out and they will extend their big toe. The lack of some of the myelination of the corticospinal tracts in young children may be the cause of this reflex.

See Also:

Galant Reflex

Galant

Galant Reflex

This reflex is present at birth and fades between the ages of four to six months, if it remains beyond that it is always pathological. [6] You can stimulate this reflex by stroking the skin along one side of a child's back. The baby will swing toward the side you stroke.

See also

References

  1. Primitive and Postural reflexes - the Theory
  2. Infantile reflexes on MedLinePlus
  3. The grasp and other primitive reflexes
  4. Infantile Reflexes Gone Astray in Autism
  5. Tilt test spots early Asperger's
  6. The Galant Reflex

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