Primitive reflexes
Encyclopedia
Primitive reflexes are reflex action
s originating in the central nervous system
that are exhibited by normal infants but not neurologically intact adults, in response to particular stimuli
. These reflexes disappear or are inhibited by the frontal lobe
s as a child moves through normal child development
. These primitive reflexes are also called infantile, infant or newborn reflexes.
Older children and adults with atypical neurology
(for instance, people with cerebral palsy
) may retain these reflexes and primitive reflexes may re-appear in adults because of certain neurological conditions including, but not limited to, dementia
, traumatic lesion
s, and stroke
s. An individual with cerebral palsy and typical intelligence can learn to suppress these reflexes, but the reflex might resurface under certain conditions such as during an extreme startle reaction
. Reflexes may also be limited to those areas affected by the atypical neurology, such as individuals whose cerebral palsy affects only their legs retaining the Babinski reflex
but having normal speech; in individuals with hemiplegia
, the reflex might be seen in the foot on the affected side only.
Primitive reflexes are primarily tested with suspected brain injury
to test the functioning of the frontal lobe. If they are not being suppressed properly they are called frontal release signs. Atypical primitive reflexes are also being researched as potential early warning signs of autistic spectrum disorders
.
This is sometimes referred to as the startle reaction
, startle response, startle reflex or embrace reflex. It is more commonly known as the Moro response or Moro reflex
after its discoverer, pediatrician Ernst Moro
.
The Moro reflex is present at birth, peaks in the first month of life and begins to disappear 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 disappears by three to four months of age, though it may last up to six months. Bilateral absence of the reflex may mean damage to the infant's central nervous system
while a unilateral absence could mean an injury due to birth trauma
such as 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 the infant cling to his mother while she carried him around all day. If the infant lost its balance, the reflex caused the infant to embrace its mother and regain its hold on the mother’s body.
The walking or stepping reflex is present at birth; though infants this young can not 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 disappears at 6 weeks due to an increased ratio of leg weight to strength. It reappears as a voluntary behavior at around eight months to a year old.
, disappearing at around four months of age as it gradually comes under voluntary control. A newborn infant
will turn his head toward anything that strokes his cheek or mouth, searching for the object by moving his head in steadily decreasing arcs until the object is found. After becoming used to responding in this way (if breastfed, approximately three weeks after birth), the infant will move directly to the object without searching.
s and is present at birth. It is linked with the rooting reflex and breastfeeding, and causes the child to instinctively suck at anything that touches the roof of their mouth and suddenly starts to suck simulating the way they naturally eat. There are two stages to the action:
The tonic neck reflex, also known as asymmetric tonic neck reflex or 'fencing posture' is present at one month of age and disappears 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 neuron
s. According to researchers, the tonic neck reflex is a precursor to the hand/eye coordination of the infant. It also prepares the infant for voluntary reaching.
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. The grip is strong but unpredictable; though 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.
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 ~1 year, because of low myelination of the corticospinal tract
s. As these tracts develop to adult form, the flexion-reflex circuit is inhibited by the descending corticospinal inputs, and the normal plantar reflex develops.. Also known as the Babinski reflex, this is a sign of neurological abnormality, e.g. upper motor neurone lesion, in adults.
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 Russia
n neurologist Johann Susman Galant.
Boris Babkin
.
They include the palmomental reflex
, snout reflex
, glabellar reflex
or "tap", in addition to some of those mentioned above.
Reflex action
A reflex action, also known as a reflex, is an involuntary and nearly instantaneous movement in response to a stimulus. A true reflex is a behavior which is mediated via the reflex arc; this does not apply to casual uses of the term 'reflex'.-See also:...
s originating in the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
that are exhibited by normal infants but not neurologically intact adults, in response to particular stimuli
Stimulus (physiology)
In physiology, a stimulus is a detectable change in the internal or external environment. The ability of an organism or organ to respond to external stimuli is called sensitivity....
. These reflexes disappear or are inhibited by the frontal lobe
Frontal lobe
The frontal lobe is an area in the brain of humans and other mammals, located at the front of each cerebral hemisphere and positioned anterior to the parietal lobe and superior and anterior to the temporal lobes...
s as a child moves through normal child development
Child development
Child development stages describe theoretical milestones of child development. Many stage models of development have been proposed, used as working concepts and in some cases asserted as nativist theories....
. These primitive reflexes are also called infantile, infant or newborn reflexes.
Older children and adults with atypical neurology
Neurology
Neurology is a medical specialty dealing with disorders of the nervous system. Specifically, it deals with the diagnosis and treatment of all categories of disease involving the central, peripheral, and autonomic nervous systems, including their coverings, blood vessels, and all effector tissue,...
(for instance, people with cerebral palsy
Cerebral palsy
Cerebral palsy is an umbrella term encompassing a group of non-progressive, non-contagious motor conditions that cause physical disability in human development, chiefly in the various areas of body movement....
) may retain these reflexes and primitive reflexes may re-appear in adults because of certain neurological conditions including, but not limited to, dementia
Dementia
Dementia is a serious loss of cognitive ability in a previously unimpaired person, beyond what might be expected from normal aging...
, traumatic lesion
Lesion
A lesion is any abnormality in the tissue of an organism , usually caused by disease or trauma. Lesion is derived from the Latin word laesio which means injury.- Types :...
s, and stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
s. An individual with cerebral palsy and typical intelligence can learn to suppress these reflexes, but the reflex might resurface under certain conditions such as during an extreme startle reaction
Startle reaction
The startle response is a brainstem reflex that serves to protect the back of the neck , or the eye , and also facilitates escape from sudden stimuli. It is found across the lifespan and in many species. An individual's emotional state may lead to a variety of different responses...
. Reflexes may also be limited to those areas affected by the atypical neurology, such as individuals whose cerebral palsy affects only their legs retaining the Babinski reflex
Plantar reflex
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 normal adults the plantar reflex causes a downward response of the hallux...
but having normal speech; in individuals with hemiplegia
Hemiplegia
Hemiplegia /he.mə.pliː.dʒiə/ is total paralysis of the arm, leg, and trunk on the same side of the body. Hemiplegia is more severe than hemiparesis, wherein one half of the body has less marked weakness....
, the reflex might be seen in the foot on the affected side only.
Primitive reflexes are primarily tested with suspected brain injury
Acquired brain injury
An acquired brain injury is brain damage caused by events after birth, rather than as part of a genetic or congenital disorder such as fetal alcohol syndrome, perinatal illness or perinatal hypoxia. ABI can result in cognitive, physical, emotional, or behavioural impairments that lead to permanent...
to test the functioning of the frontal lobe. If they are not being suppressed properly they are called frontal release signs. Atypical primitive reflexes are also being researched as potential early warning signs of autistic spectrum disorders
Autism
Autism is a disorder of neural development characterized by impaired social interaction and communication, and by restricted and repetitive behavior. These signs all begin before a child is three years old. Autism affects information processing in the brain by altering how nerve cells and their...
.
Adaptive value of reflexes
Reflexes vary in utility. Some have a survival value. A perfect example would be the rooting reflex, which helps a breastfed infant find the mother's nipple. Babies display it only when hungry and touched by another person, not when they touch themselves. There are a few reflexes that probably helped babies survive during human evolutionary past like 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 lovingly and feed more competently. They can also help parents comfort their infant because they allow the baby to control distress and the amount of stimulation they receive.Moro reflex
Startle reaction
The startle response is a brainstem reflex that serves to protect the back of the neck , or the eye , and also facilitates escape from sudden stimuli. It is found across the lifespan and in many species. An individual's emotional state may lead to a variety of different responses...
, startle response, startle reflex or embrace reflex. It is more commonly known as the Moro response or Moro reflex
Moro reflex
The Moro reflex, which is distinct from the startle reflex, is one of the infantile reflexes.It may be observed in incomplete form in premature birth after the 28th week of gestation, and is usually present in complete form by week 34...
after its discoverer, pediatrician Ernst Moro
Ernst Moro
Ernst Moro was an Austrian physician and pediatrician who discovered the infant reflex which was named after him ....
.
The Moro reflex is present at birth, peaks in the first month of life and begins to disappear 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 disappears by three to four months of age, though it may last up to six months. Bilateral absence of the reflex may mean damage to the infant's central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
while a unilateral absence could mean an injury due to birth trauma
Birth trauma
Birth trauma may refer to:* Pre- and perinatal psychology, the psychological trauma that is sometimes experienced during childbirth*Birth trauma , physical trauma of childbirth, as described at ICD-10 codes P10-P15....
such as a fractured clavicle
Clavicle fracture
A clavicle fracture is a bone fracture in the clavicle, or collarbone. It is often caused by a fall onto an outstretched upper extremity, a fall onto a shoulder, or a direct blow to the clavicle...
or injury to the brachial plexus
Brachial plexus
The brachial plexus is a network of nerve fibers, running from the spine, formed by the ventral rami of the lower four cervical and first thoracic nerve roots...
. Erb's palsy
Erb's palsy
Erb's palsy is a paralysis of the arm caused by injury to the upper group of the arm's main nerves, specifically the upper trunk C5-C6 is severed. These form part of the brachial plexus, comprising the ventral rami of spinal nerves C5-C8, and T1. These injuries arise most commonly, but not...
or some other form of paralysis
Paralysis
Paralysis is loss of muscle function for one or more muscles. Paralysis can be accompanied by a loss of feeling in the affected area if there is sensory damage as well as motor. A study conducted by the Christopher & Dana Reeve Foundation, suggests that about 1 in 50 people have been diagnosed...
is also sometimes present in such cases. In human evolutionary history, the Moro reflex may have helped the infant cling to his mother while she carried him around all day. 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
WALK
WALK may refer to:*WALK , a radio station licensed to East Patchogue, New York, United States*WALK-FM, a radio station licensed to Patchogue, New York, United States...
' by placing one foot in front of the other. This reflex disappears at 6 weeks due to an increased ratio of leg weight to strength. It reappears as a voluntary behavior at around eight months to a year old.
Rooting reflex
The rooting reflex is present at birth; it assists in breastfeedingBreastfeeding
Breastfeeding is the feeding of an infant or young child with breast milk directly from female human breasts rather than from a baby bottle or other container. Babies have a sucking reflex that enables them to suck and swallow milk. It is recommended that mothers breastfeed for six months or...
, disappearing at around four months of age as it gradually comes under voluntary control. A newborn infant
Infant
A newborn or baby is the very young offspring of a human or other mammal. A newborn is an infant who is within hours, days, or up to a few weeks from birth. In medical contexts, newborn or neonate refers to an infant in the first 28 days after birth...
will turn his head toward anything that strokes his cheek or mouth, searching for the object by moving his head in steadily decreasing arcs until the object is found. After becoming used to responding in this way (if breastfed, approximately three weeks after birth), the infant will move directly to the object without searching.
Sucking reflex
The sucking reflex is common to all mammalMammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s and is present at birth. It is linked with the rooting reflex and breastfeeding, and causes the child to instinctively suck at anything that touches the roof of their mouth and suddenly starts to suck simulating the way they naturally eat. There are two stages to the action:
- Expression: activated when the nippleNippleIn its most general form, a nipple is a structure from which a fluid emanates. More specifically, it is the projection on the breasts or udder of a mammal by which breast milk is delivered to a mother's young. In this sense, it is often called a teat, especially when referring to non-humans, and...
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 areolaAreolaThis article is about the breast tissue. For the entomology term, see the glossary of Lepidopteran terms. For an artistic cloud motif, see aureola. For the cactus feature, see Areole....
to nipple, coaxing milk from the mother to be swallowed by the child.
Tonic neck reflex
The tonic neck reflex, also known as asymmetric tonic neck reflex or 'fencing posture' is present at one month of age and disappears 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 neuron
Upper motor neuron
Upper motor neurons are motor neurons that originate in the motor region of the cerebral cortex or the brain stem and carry motor information down to the final common pathway, that is, any motor neurons that are not directly responsible for stimulating the target muscle...
s. According to researchers, the tonic neck reflex is a precursor to the hand/eye coordination of the infant. It also prepares the infant for voluntary reaching.
Palmar grasp reflex
Plantar reflex
A plantar reflex is a normal reflex that involves plantar flexion of the foot (toes move away from the shin, and curl down. An abnormal plantar reflex (aka BabinskiJoseph Babinski
Joseph Jules François Félix Babinski was a French neurologist of Polish descent. He is best known for his 1896 description of the Babinski sign, a pathological plantar reflex indicative of corticospinal tract damage....
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 ~1 year, because of low myelination of the corticospinal tract
Corticospinal tract
The corticospinal or pyramidal tract is a collection of axons that travel between the cerebral cortex of the brain and the spinal cord....
s. As these tracts develop to adult form, the flexion-reflex circuit is inhibited by the descending corticospinal inputs, and the normal plantar reflex develops.. Also known as the Babinski reflex, this is a sign of neurological abnormality, e.g. upper motor neurone lesion, in adults.
Galant reflex
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 Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
n neurologist Johann Susman Galant.
Swimming Reflex
An infant placed face down in a pool of water will begin to paddle and kick in a swimming motion. The reflex disappears between 4–6 months. Its survival function is to help the child stay alive if it is drowning so a caregiver has more time to save it. Although the infant will begin to paddle and kick, placing them in water is very risky. They swallow a large amount of water at the same time. It is advisable to postpone swimming lessons in infants until they are at least three months old.Babkin reflex
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 or opening of the mouth, or a combination of these responses. Smaller, premature infants are more susceptible to the reflex, with an observed occurrence in a child of 26 weeks gestation. It is named for Russian neurologistNeurologist
A neurologist is a physician who specializes in neurology, and is trained to investigate, or diagnose and treat neurological disorders.Neurology is the medical specialty related to the human nervous system. The nervous system encompasses the brain, spinal cord, and peripheral nerves. A specialist...
Boris Babkin
Boris Babkin
Boris Petrovitch Babkin, M.D., D.Sc, LL.D was a Russian-born physiologist, who worked in Russia, England and Canada.- Career :...
.
Other primitive reflexes tested in adults
As mentioned these are generally referred to as frontal release signs although this may be a misnomer.They include the palmomental reflex
Palmomental reflex
The palmomental reflex is a primitive reflex consisting of a twitch of the chin muscle elicited by stroking a specific part of the palm. It is present in infancy and disappears as the brain matures during childhood but may reappear due to processes that disrupt the normal cortical inhibitory...
, snout reflex
Snout reflex
The Snout reflex is a pouting or pursing of the lips that is elicited by light tapping of the closed lips near the midline. The contraction of the muscles causes the mouth to resemble a snout....
, glabellar reflex
Glabellar reflex
Glabellar reflex is a primitive reflex. It is elicited by repetitive tapping on the forehead. Subjects blink in response to the first several taps...
or "tap", in addition to some of those mentioned above.