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.[1] 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.[2][3] 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.[4]
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.[5][6][7]
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.[8]
Sucking reflex
The sucking reflex is common to all mammals and is present at birth. 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:[citation needed]
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.[9]
The Moro reflex in a four-day-old infant: 1) the reflex is initiated by pulling the infant up from the floor and then releasing him; 2) he spreads his arms 3) he pulls his arms in; 4) he cries (10 seconds)
The Moro reflex is an important indicator for evaluating integration of the central nervous system, named after its discoverer, pediatricianErnst 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,[10] and it is believed to be the only unlearned fear in human newborns.[citation needed]
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.[clarification needed] Shortly afterward the arms are brought together and the hands clench into fists, and the infant cries loudly.[11]
The reflex normally integrates by three to four months of age,[12] though it may last up to six months.[13]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.[12] 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.[8]
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.[14]
The asymmetrical tonic neck reflex (ATNR) in a two-week-old female, with extension of the left extremities and flexion of the right.
The asymmetrical tonic neck reflex, also known as 'fencing posture', is present at one month of age and integrates at around four months. When the child's head is turned to the side, the arm on that side will straighten and the opposite arm will bend (sometimes the motion will be very subtle or slight). If the infant is unable to move out of this position or the reflex continues to be triggered past six months of age, the child may have a disorder of the upper motor neurons. According to Laura Berk, the tonic neck reflex is a precursor to the hand/eye coordination of the infant. It also prepares the infant for voluntary reaching.[8]
The symmetric tonic neck reflex normally appears and develops around 6–9 months of age and should integrate by around 12 months. When the child's head flexes forward, extending the back of the neck, the upper extremities will contract and the lower extremities will extend. Conversely, when the child's head is extended backward, contracting the back of the neck, the upper extremities will extend and the lower extremities will contract. This reflex is important to help a child push up onto their hands and knees but may inhibit actual forward creeping or crawling if it is not properly integrated. If this reflex is retained beyond 2–3 years, it may result, directly or indirectly, in a range of physical and neurological developmental delays.[15][16]
The tonic labyrinthine reflex is a primitive reflex found in newborn humans. With this reflex, tilting the head back while lying on the back causes the back to stiffen and even arch backwards, the legs to straighten, stiffen, and push together, the toes to point, the arms to bend at the elbows and wrists, and the hands to become fisted or the fingers to curl. The presence of this reflex beyond the newborn stage is also referred to as abnormal extension pattern or extensor tone.[citation needed]
The presence of the TLR as well as other primitive reflexes such as the asymmetrical tonic neck reflex (ATNR) beyond the first six months of life may indicate that the child has developmental delays and/or neurological abnormalities.[17] For example, in people with cerebral palsy, the reflexes may persist and even be more pronounced. As abnormal reflexes, both the tonic labyrinthine reflex and the asymmetrical tonic neck reflex can cause problems for the growing child. The TLR and ATNR both hinder functional activities such as rolling, bringing the hands together, or even bringing the hands to the mouth. Over time, both the TLR and ATNR can cause serious damage to the growing child's joints and bones, causing the head of the femur to partially slip out of the acetabulum (subluxation) or completely move out of the acetabulum (dislocation).[citation needed]
The palmar grasp reflex appears at birth and persists until five or six months of age. When an object is placed in the infant's hand and strokes their palm, the fingers will close and they will grasp it with a palmar grasp. To best observe this reflex, on a bed where the child could safely fall onto a pillow, offer the infant two opposing little fingers (as index fingers are typically too large for the infant to grasp), and gradually lift. The grasp of it may be able to support the child's weight; they may also release their grip suddenly and without warning. The reverse motion can be induced by stroking the back or side of the hand.[18]
A plantar reflex is a normal reflex that involves plantar flexion of the foot, which moves toes away from the shin and curls them down. An abnormal plantar reflex (Babinski sign) occurs when upper motor neuron control over the flexion reflex circuit is interrupted. This results in a dorsiflexion of the foot (foot angles towards the shin, big toe curls up). This also occurs in babies under c. 1 year, because of low myelination of the corticospinal tracts. As these tracts develop to adult form, the flexion-reflex circuit is inhibited by the descending corticospinal inputs, and the normal plantar reflex develops.[19] The Babinski reflex is a sign of neurological abnormality (e.g., upper motor neuron lesion) in adults.[20]
The Galant reflex, also known as Galant's infantile reflex, is present at birth and fades between the ages of four to six months. When the skin along the side of an infant's back is stroked, the infant will swing towards the side that was stroked. If the reflex persists past six months of age, it is a sign of pathology. The reflex is named after the Russian neurologist Johann Susman Galant.[21]
The swimming reflex involves placing an infant face down in a pool of water. The infant will begin to paddle and kick in a swimming motion. The reflex disappears between 4–6 months. Despite the infant displaying a normal response by paddling and kicking, placing them in water can be a very risky procedure. Infants can swallow a large amount of water while performing this task; therefore, caregivers should proceed with caution. It is advisable to postpone swimming lessons for infants until they are at least three months old because infants submerged in water can die from water intoxication.[8]
Babkin reflex
An infant demonstrating the Babkin reflex: he opens his mouth when pressure is applied to both palms (8 seconds).
The Babkin reflex occurs in newborn babies, and describes varying responses to the application of pressure to both palms. Infants may display head flexion, head rotation, opening of the mouth, or a combination of these responses.[22] Smaller, premature infants are more susceptible to the reflex, with an observed occurrence in a child of 26 weeks gestation.[23] It is named after the Russian physiologist, Boris Babkin.[citation needed]
Parachute reflex
This reflex occurs in slightly older infants (starts between 6 and 7 months[24] and become fully mature by 1 year of age) when the child is held upright and the baby's body is rotated quickly to face forward (as in falling). The baby will extend their arms forward as if to break a fall, even though this reflex appears long before the baby walks.[citation needed]
Unintegrated reflexes
Reflexes that are not suppressed in infancy are referred to as unintegrated or persistent reflexes. When they persist, they are related to academic struggles. For example, children with learning difficulties have been found to exhibit persistent primitive reflexes.[25] In addition, a persistent ATNR has been found to be associated with lower reading and spelling scores,[26] and children with reading problems tend to display the tonic labyrinthine reflex more than children without reading problems.[27] Upon monitoring pre-primary school children to see how reflexes develop as an infant gets older, the strongest association of all motor skills was found between static and dynamic balance and performance in academic activities such as mathematics.[28] There has also been a high correlation found between ATNR persistence and decreased fine motor skills in children, which in many cases has led to a diagnosis of motor deficit disorders such as Developmental Coordination Disorder (DCD).[28] Lastly, a relationship has been found between ADHD symptoms and ATNR persistence[29] and another between ADHD diagnosis and Moro and Galant reflex persistence.[30]
Other primitive reflexes tested in adults
As mentioned in the introduction, when primitive reflexes are not being suppressed properly they are generally referred to as frontal release signs (although this may be a misnomer). In addition to the reflexes previously mentioned, they include the palmomental reflex, snout reflex, glabellar reflex or "tap" reflex.[citation needed]
Primitive reflexes in high-risk newborns
The term high-risk newborns refers to neonates with a significant chance of mortality or morbidity, especially within the first month of being born. High-risk newborns will often show abnormal responses of primitive reflexes, or lack a response entirely. Performance of primitive reflexes in high-risk newborns will often vary in response depending on the reflex (e.g., normal Moro reflex may be present, while the walking reflex is absent or abnormal). Normal performance of primitive reflexes in newborns can be linked to a greater likelihood of having higher Apgar scores, higher birth weight, shorter hospitalization time after birth, and a better overall mental state.[citation needed]
A 2011 cross-sectional study assessing primitive reflexes in 67 high-risk newborns, used a sample method to evaluate responses of the sucking, Babinski and Moro reflexes. The results of the study showed that the sucking reflex was performed normally most often (63.5%), followed by the Babinski reflex (58.7%), and the Moro reflex (42.9%). The study concluded that high-risk newborns presented more periodic abnormal and absent responses of primitive reflexes, and that each reflex varied in response.[31]
However, with the advent of simple and effective methods like the Amiel Tison method of neurological assessment, as predictor of neurological sequelae in high-risk neonates and infants, the importance of assessment of primitive reflexes is decreasing.[5][6][7]
In biology, a reflex, or reflex action, is an involuntary, unplanned sequence or action and nearly instantaneous response to a stimulus.
The Neonatal Behavioral Assessment Scale (NBAS), also known as the Brazelton Neonatal Assessment Scale (BNAS), was developed in 1973 by T. Berry Brazelton and his colleagues. This test purports to provide an index of a newborn's abilities, and is usually given to an infant somewhere between the age of 3 days to 4 weeks old. The test is designed to describe the neonate's response to the environment after being born. This approach was innovative for recognizing that a baby is a highly developed organism, even when just newly born. The profile describes the baby's strengths, adaptive responses and possible vulnerabilities. This knowledge may help parents develop appropriate strategies for caring in intimate relationships to enhance their earliest relationship with the child.
The plantar reflex is a reflex elicited when the sole of the foot is stimulated with a blunt instrument. The reflex can take one of two forms. In healthy adults, the plantar reflex causes a downward response of the hallux (flexion).
The Moro reflex is an infantile reflex that develops between 28 and 32 weeks of gestation and disappears at 3–6 months of age. It is a response to a sudden loss of support and involves three distinct components:
spreading out the arms (abduction)
pulling the arms in (adduction)
crying (usually)
An upper motor neuron lesion Is an injury or abnormality that occurs in the neural pathway above the anterior horn cell of the spinal cord or motor nuclei of the cranial nerves. Conversely, a lower motor neuron lesion affects nerve fibers traveling from the anterior horn of the spinal cord or the cranial motor nuclei to the relevant muscle(s).
The vestibulospinal tract is a nerve tract in the central nervous system. Specifically, it is a component of the extrapyramidal system and is classified as a component of the medial pathway. Like other descending motor pathways, the vestibulospinal fibers of the tract relay information from nuclei to motor neurons. The vestibular nuclei receive information through the vestibulocochlear nerve about changes in the orientation of the head. The nuclei relay motor commands through the vestibulospinal tract. The function of these motor commands is to alter muscle tone, extend, and change the position of the limbs and head with the goal of supporting posture and maintaining balance of the body and head.
Child development stages are the theoretical milestones of child development, some of which are asserted in nativist theories. This article discusses the most widely accepted developmental stages in children. There exists a wide variation in terms of what is considered "normal", caused by variations in genetic, cognitive, physical, family, cultural, nutritional, educational, and environmental factors. Many children reach some or most of these milestones at different times from the norm.
A reflex hammer is a medical instrument used by practitioners to test deep tendon reflexes, the best known possibly being the patellar reflex. Testing for reflexes is an important part of the neurological physical examination in order to detect abnormalities in the central or peripheral nervous system.
Galant reflex, or truncal incurvation reflex, is a newborn reflex, named after neurologist Johann Susmann Galant. It is elicited by holding the newborn in ventral suspension and stroking along the one side of the spine. The normal reaction is for the newborn to laterally flex toward the stimulated side.
The asymmetrical tonic neck reflex (ATNR) is a primitive reflex found in newborn humans that normally vanishes around 6 months of age. It is also known as the bow and arrow or "fencing reflex" because of the characteristic position of the infant's arms and head, which resembles that of a fencer. When the face is turned to one side, the arm and leg on that side extend, and the arm and leg on the opposite side flex. It is more likely to be seen in premature infants than full-term babies. It is rare in newborns but can be stimulated from infants to up to 3 months old. It is believed to help develop hand-eye coordination and help with awareness of both sides of the body.
The tonic labyrinthine reflex (TLR) is a primitive reflex found in newborn humans. With this reflex, tilting the head back (extension) while lying on the stomach causes the back to stiffen and even arch backwards, the legs to straighten, stiffen, and push together, the toes to point, the arms to straighten. The reverse happens to arms and legs with neck flexion. The presence of this reflex beyond the newborn stage is also referred to as abnormal extension pattern or extensor tone.
Hoffmann's reflex is a neurological examination finding elicited by a reflex test which can help verify the presence or absence of issues arising from the corticospinal tract. It is named after neurologist Johann Hoffmann. Usually considered a pathological reflex in a clinical setting, the Hoffmann's reflex has also been used as a measure of spinal reflex processing (adaptation) in response to exercise training.
Frontal release signs are primitive reflexes traditionally held to be a sign of disorders that affect the frontal lobes. The appearance of such signs reflects the area of brain dysfunction rather than a specific disorder which may be diffuse, such as a dementia, or localised, such as a tumor.
The palmar grasp reflex is a primitive and involuntary reflex found in infants of humans and most primates. When an object, such as an adult finger, is placed in an infant's palm, the infant's fingers reflexively grasp the object. Placement of the object triggers a spinal reflex, resulting from stimulation of tendons in the palm, that gets transmitted through motor neurons in the median and ulnar sensory nerves. The reverse motion can be induced by stroking the back or side of the hand. A fetus exhibits the reflex in utero by 28 weeks into gestation, and persists until development of rudimentary fine motor skills between two and six months of age.
The fencing response is an unnatural position of the arms following a concussion. Immediately after moderate forces have been applied to the brainstem, the forearms are held flexed or extended for a period lasting up to several seconds after the impact. The fencing response is often observed during athletic competition involving contact, such as combat sports, American football, ice hockey, rugby union, rugby league and Australian rules football. It is used as an overt indicator of injury force magnitude and midbrain localization to aid in injury identification and classification for events including on-field and/or bystander observations of sports-related head injuries.
Babinski–Nageotte syndrome is an alternating brainstem syndrome. It occurs when there is damage to the dorsolateral or posterior lateral medulla oblongata, likely syphilitic in origin. Hence it is also called the alternating medulla oblongata syndrome.
A general movements assessment is a type of medical assessment used in the diagnosis of cerebral palsy, and is particularly used to follow up high-risk neonatal cases. The general movements assessment involves measuring movements that occur spontaneously among those less than four months of age and appears to be most accurate test for the condition.
Infant swimming is the phenomenon of human babies and toddlers reflexively moving themselves through water and changing their rate of respiration and heart rate in response to being submerged. The slowing of heart rate and breathing is called the bradycardic response. It is not true that babies are born with the ability to swim, though they have primitive reflexes that make it look like they are. Newborns are not old enough to hold their breath intentionally or strong enough to keep their head above water, and cannot swim unassisted.
The symmetrical tonic neck reflex (STNR) is a primitive reflex that normally emerges during the first month of an infant's life and is diminished by the age of 9–10 months. It is a bridging or transitional brainstem reflex that is an important developmental stage and is necessary for a baby to transition from lying on the floor to quadruped crawling or walking. In order to progress beyond this development stage, the baby needs to have been successful in unlinking the automatic movement of the head from the automatic movement of the arms and legs.
1 2 3 4 Berk, Laura E.. Child Development. 8th. US: Pearson, 2009.
↑ Odent M. The early expression of the rooting reflex. Proceedings of the 5th International Congress of Psychosomatic Obstetrics and Gynaecology, Rome 1977. London: Academic Press, 1977: 1117-19.
↑ Pedroso, Fleming S.; Rotta, Newra T. (2004). "Babkin Reflex and Other Motor Responses to Appendicular Compression Stimulus of the Newborn". Journal of Child Neurology. 19 (8): 592–596. doi:10.1177/088307380401900805. PMID15605468. S2CID22525789.
↑ Konicarova, J.; Bob, P. (2013). "Asymmetric tonic neck reflex and symptoms of attention deficit and hyperactivity disorder in children". International Journal of Neuroscience. 123 (11): 766–9. doi:10.3109/00207454.2013.801471. PMID23659315. S2CID16007573.
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