Primitive reflexes are automatic, physiological movement responses of an infant, which are fully developed at the time of birth and continue until the completed first year of life. From a developmental point of view, they are of great importance for the survival of the child. Absence or persistence of individual reflexes is considered pathological and usually has negative effects on the child’s development.
What is a primitive reflex?
Primitive reflexes are physiologic during the first few weeks of life and regress as brain development progresses within the first year of life. Primitive reflexes are also referred to as early infant or neonatal reflexes. They describe a reproducible reaction pattern of the infant to external stimuli. A distinction is made between reflexes of feeding as well as holding, position and movement reflexes. The sequences of the reactions are only minimally variable and cannot be influenced arbitrarily by the infant. The primitive reflexes are physiological during the first weeks of life and regress as brain development progresses within the first year of life. Each individual reflex is assigned to a specific area of the central nervous system and is mediated through the diencephalon. As development progresses and the neural pathways of higher brain centers become myelinated, these primitive responses are suppressed. A prerequisite for this is the infant’s ability to move freely and gain control over its own body through initially random motor processes.
Function and task
From an evolutionary perspective, early childhood reflexes have an important function in a child’s survival. Today, due to the protected environment in which the infant spends its first year of life, they have lost much of their vital functions, but they remain a fixed part of pediatric screening. Here, various tests can be used to draw conclusions about physiological development, among other things. Missing or asymmetrical reflexes as well as their persistence over a certain period of time indicate neurological disorders. The reflexes of food intake consist of the search reflex, the sucking reflex and the swallowing reflex. Through them, the infant actively turns toward the mother’s breast, opens the mouth, and begins to suck. Until the third or fourth month of life, the infant’s intake of food is therefore exclusively reflexive. The holding, position and movement reflexes are also present for the most part from birth. The Galant reflex is triggered by stroking along the spine and causes the trunk to curve to the stimulated side. This reflex may have its origin in the birth process by allowing the child to move in the birth canal. Also involved in birth is the asymmetric tonic neck reflex, which triggers extension of the extremities on the same side and flexion of the extremities on the opposite side when the head is turned. In addition, this reflex allows the infant to breathe freely in the prone position. This is in contrast to the tonic labyrinth reflex, which results in flexion or extension of the entire body when the head is moved. Its effect is later cancelled by the symmetric tonic neck reflex. Immediately after birth, the infant has several reflexes with evolutionary background. The infant can hold its position by the grasp reflex as well as the Moro reflex. In the grasping reflex, the infant automatically closes the hand into a fist when touching the palm. The same works with the sole of the foot, suggesting a connection to the animal world. The reflex enables newborn monkeys, for example, to hold on to the fur of the mother animal. The Moro reflex works in a similar way, triggering a startle reaction in the infant as soon as it is jerkily placed backwards. As a result, it pulls its arms to its chest and assumes a clinging posture designed to prevent it from falling backward.
Diseases and ailments
Early infant reflexes are important to the newborn and are physiologic until a certain month of life. Attenuated, absent, or persistent reflexes indicate a neurologic disorder and may adversely affect the child’s development. If the search, suck and swallow reflexes are absent, the infant does not take in enough food.If, on the other hand, the reflexes are too pronounced or do not regress on their own, the children are later hypersensitive in the mouth area and have a strong salivation, which impairs the development of speech. Rejection of solid food negatively affects the development of the mouth muscles, making swallowing, chewing and saliva control difficult. If the infant’s motor learning is inadequate, the higher neural pathways become less myelinated and thus the primitive reflexes are not suppressed. Some reflexes, when pathologized, have negative effects on motor development. The asymmetric tonic neck reflex provides the infant with initial training in eye-hand coordination but, if persistent, may cause balance disturbances and inadequate tonicity when the head is turned. The tonic labyrinth reflex has similar effects on balance. Poor spatial perception and thus an inadequate ability to orient may result. If the symmetric tonic neck reflex persists, it is impossible for the infant to crawl or sit up. Some reflexes, such as the palmar grasp reflex, may reappear in adulthood in the course of a neurological disease. These reflexes are then no longer physiological, but are assigned to pathology due to disease. The Babinski reflex, which leads to an extension of the big toe with simultaneous flexion of the other toes when stroking the sole of the foot, can normally no longer be triggered after the 12th month of life. After massive brain damage, such as from a stroke, or after traumatic impact on the brain, the reflex may reappear.
