Palmar grasp reflex


Palmar grasp reflex is a primitive reflex found in infants of humans and most primates. When an object is placed in an infant's hand and the palm of the child is stroked, the fingers will close reflexively, as the object is grasped via palmar grasp. 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.
A fetus can exhibit the reflex in utero as early as 16 weeks into the gestation period, and persists until five or six months of age.

Significance

Biologists have found that the reflex is significantly more frequent in infants of fur carrying primate species. They theorize that the grasping reflex evolved as it is essential to survival in species where the young are carried in the fur. This suggests that the grasping reflex is vestigial in humans and in other non-fur carrying primates.

Medical diagnostic

In humans, if the palmar grasp reflex persists beyond 2 to 4 months, it delays or affects functions like grasping a rattle, releasing objects from hand and also hand manipulation skills. Palmar grasp reflex in adults is a pathological frontal release sign and may signify frontal lobe damage, or may be a sign of anterior cerebral artery syndrome.