Primitive reflex

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(aka Frontal release signs)

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Primitive reflexes are also called infantile reflexes, infant reflexes, or newborn reflexes. They are reflexes present on humans in the infantile period. Infants have many reflexes that exist at birth or develop shortly after and gradually disappear as the infant develops. Some with obvious purposes, some are clearly vestigal and some do not have obvious purposes. The frontal lobes are responsible for suppressing these primitive reflexes in adults.

Primitive reflexes reappear in adults under certain conditions. Namely, neurological conditions like dementia, traumatic lesions, etc.

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 iunjury, neurologists test the primitive reflexes to identify the location of the lesion because primitive reflexes originate from the frontal lobe, hence called frontal release signs.

[edit] Primitive reflexes

Moro reflex (startle reflex)
Asymmetrical tonic neck reflex (fencer's reflex)
Sucking reflex, suckling reflex: it can be initiated by scratching the infants cheek and the reaction is pursing of the lips for sucking, that's why it is also called sucking reflex.
Rooting reflex: it can be initiated by touching the infant's cheek. The infant turn the head to the direction of the tactile sensation to expect mother's nipple.
Stepping reflex, step-up reflex: it can be initiated if you support the infant upright from its armpits below a given surface so the baby lifts its foot and steps up on the surface (like climbing a stair).
Grasp reflex: it can be initiated by scratching baby's palm.
Parachute reflex
Plantar reflex or Babinski reflex: movement of the big toe when the sole of the foot is scratched