Primitive reflexes are reflex actions originating in the central nervous system that are exhibited by normal infants, but not neurologically intact adults, in response to particular stimuli. These reflexes are suppressed by the development of the frontal lobes as a child transitions normally into child development. These primitive reflexes are also called infantile, infant or newborn reflexes. Older children and adults with atypical neurology (e.g., people with cerebral palsy) may retain these reflexes and primitive reflexes may reappear in adults. Reappearance may be attributed to certain neurological conditions including dementia (especially in a rare set of diseases called frontotemporal degenerations), traumatic lesions, and strokes. An individual with cerebral palsy and typical intelligence can learn to suppress these reflexes, but the reflex might resurface under certain conditions (i.e., during extreme startle reaction). Reflexes may also be limited to those areas affected by the atypical neurology, (i.e., individuals with cerebral palsy that only affects their legs retaining the Babinski reflex but having normal speech); for those individuals with hemiplegia, the reflex may be seen in the foot on the affected side only. Primitive reflexes are primarily tested with suspected brain injury or some dementias such as Parkinson's disease for the purpose of assessing frontal lobe functioning. If they are not being suppressed properly they are called frontal release signs. Atypical primitive reflexes are also being researched as potential early indicators of autistic spectrum disorders. Primitive reflexes are mediated by extrapyramidal functions, many of which are already present at birth. They are lost as the pyramidal tracts gain functionality with progressive myelination. They may reappear in adults or children with loss of function of the pyramidal system due to a variety of reasons. However, with the advent of Amiel Tison method of neurological assessment, the importance of assessment of such reflexes in the pediatric population has come down.
Adaptive value of reflexes Reflexes vary in utility. Some reflexes hold a survival value (e.g., the rooting reflex, which helps a breastfed infant find the mother's nipple). Babies display the rooting reflex only when they are hungry and touched by another person, not when they touch themselves. There are a few reflexes that likely assisted in the survival of babies during human evolutionary past (e.g., the Moro reflex). Other reflexes such as sucking and grabbing help establish gratifying interaction between parents and infants. They can encourage a parent to respond with love and affection, and to feed their child more competently. In addition, it helps parents to comfort their infant while allowing the baby to control distress and the amount of stimulation they receive.
Sucking reflex
The sucking reflex is common to all mammals and is present at birth(gestational age of appearance 32 to 36 weeks). It is linked with the rooting reflex and breastfeeding. It causes the child to instinctively suck anything that touches the roof of their mouth and simulates the way a child naturally eats. There are two stages of the action:
Expression: 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. Milking: The tongue moves from areola to nipple, coaxing milk from the mother to be swallowed by the child.
Rooting reflex The rooting reflex is present at birth (gestational age of appearance 28 weeks) and disappears around four months of age, as it gradually comes under voluntary control. The rooting reflex assists in the act of breastfeeding. A newborn infant will turn its head toward anything that strokes its cheek or mouth, searching for the object by moving its head in steadily decreasing arcs until the object is found. After becoming familiar to responding in this way (if breastfed, approximately three weeks after birth), the infant will move directly to the object without searching.
Moro reflex
The Moro reflex is an important indicator for evaluating integration of the central nervous system, named after its discoverer, pediatrician Ernst Moro. Although this is sometimes referred to as the startle reaction, startle response, startle reflex or embrace reflex, most researchers see it as distinct from the startle reflex, and it is believed to be the only unlearned fear in human newborns. The Moro reflex is present at birth, peaks in the first month of life, and begins to integrate around 2 months of age. It is likely to occur if the infant's head suddenly shifts position, the temperature changes abruptly, or they are startled by a sudden noise. The legs and head extend while the arms jerk up and out with the palms up and thumbs flexed. Shortly afterward the arms are brought together and the hands clench into fists, and the infant cries loudly. The reflex normally integrates by three to four months of age, though it may last up to six months. Bilateral absence of the reflex may be linked to damage to the infant's central nervous system, while a unilateral absence could mean an injury due to birth trauma (e.g., a fractured clavicle or injury to the brachial plexus). Erb's palsy or some other form of paralysis is also sometimes present in such cases. In human evolutionary history, the Moro reflex may have helped infants cling to the mother while being carried around. If the infant lost its balance, the reflex caused the infant to embrace its mother and regain its hold on the mother's body.
Walking/stepping reflex The walking or stepping reflex is present at birth, though infants this young cannot support their own weight. When the soles of their feet touch a flat surface they will attempt to walk by placing one foot in front of the other. This reflex integrates around 2 months as infants start attempting to walk after this reflex disappears.
Asymmetrical tonic neck reflex (ATNR)
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