Palmar grasp reflex

The palmar grasp reflex (or 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.[1] 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.[2][3] The reverse motion can be induced by stroking the back or side of the hand.[3] A fetus exhibits the reflex in utero by 28 weeks into gestation (sometimes, as early as 16 weeks[4]),[5][6][7] and persists until development of rudimentary fine motor skills between two and six months of age.[1][8][9][10]

Infant grasping adult finger

Evolutionary significance

Biologists have found that the reflex is significantly more frequent in infants of fur carrying primate species. It is theorized that the grasping reflex evolved as it is essential to survival in species, usually primates, where the young are carried in the fur. The infant's ability to grasp onto a mother's fur allows the mother to keep the infant with her while foraging for food or moving from one place to another. This is beneficial to the mother because she does not lose function of her limbs or mouth (as she would from oral carrying). Carrying the infant with the mother also gives a degree of safety to the infant, which it would not have if it were left in a nest or other location away from the mother. The grasp reflex also allows young individuals to have more developed food manipulation and dexterity skills. This suggests that the grasping reflex is vestigial in humans and in other non-fur carrying primates.[11] The reflex is also suggested to create a basis for which the voluntary grasping action originates. This comes from the maturation of higher motor centers, allowing a child to exert more control over the body.[2]

Clinical significance

In humans, absence of the palmar grasp reflex or persistence of the reflex can both be indicators of neurodevelopmental abnormalities. In a normal infant, the palmar grasp reflex is present during the first three months of age and disappears by six months of age. Disappearance of the reflex has been attributed to conscious and voluntary hand use.[3] Based on collected evidence, there is no significant difference between the reflexes of normal-term and pre-term infants.[2][3]

Absence of the grasp reflex could indicate a neural communication error with the spinal cord. In other words, signals from the stimulation of tendons in the palm are being interrupted before they have a chance to make it to the spinal cord, resulting in a lack of the reflex.[3] Absence of the grasp reflex could also be an indicator of peripheral nerve injury or injury to the spinal cord.[2] Persistence of the grasp reflex could be an indication of brain lesions or cerebral palsy.[2][3] Presence of the reflex in infants older than four months could be an indicator of damage to the central nervous system. This damage could be a result of neural degeneration, lack of oxygen in the brain, or other genetic factors. Any abnormal response for this reflex could produce suspicion for an underlying disease that would need to be addressed. That is why the elicitation of this grasp reflex is part of neurological examinations for newborns.[2]

References
  1. Swaiman, Kenneth F.; Phillips, John (2017-01-01), Swaiman, Kenneth F.; Ashwal, Stephen; Ferriero, Donna M.; Schor, Nina F. (eds.), "3 - Neurologic Examination after the Newborn Period Until 2 Years of Age", Swaiman's Pediatric Neurology (Sixth Edition), Elsevier, pp. 14–19, ISBN 978-0-323-37101-8, retrieved 2021-01-04
  2. Anekar, Aabha A.; Bordoni, Bruno (2021), "Palmar Grasp Reflex", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID 31985926, retrieved 2021-10-28
  3. Futagi, Yasuyuki; Toribe, Yasuhisa; Suzuki, Yasuhiro (2012). "The Grasp Reflex and Moro Reflex in Infants: Hierarchy of Primitive Reflex Responses". International Journal of Pediatrics. 2012: 191562. doi:10.1155/2012/191562. PMC 3384944. PMID 22778756.
  4. Sherer, DM (June 1993). "Fetal grasping at 16 weeks' gestation". Journal of Ultrasound in Medicine. 12 (6): 316. doi:10.7863/jum.1993.12.6.316. PMID 8515527. S2CID 21202088.
  5. Jakobovits, AA (2009). "Grasping activity in utero: a significant indicator of fetal behavior (the role of the grasping reflex in fetal ethology)". Journal of Perinatal Medicine. 37 (5): 571–2. doi:10.1515/JPM.2009.094. PMID 19492927. S2CID 26736429.
  6. Jakobovits, A (2 September 2007). "[Grasping reflex activity in utero is one element of fetal behavior (Grasping activity is a part of fetal ethology)]". Orvosi Hetilap (in Hungarian). 148 (35): 1673–5. doi:10.1556/OH.2007.28089. PMID 17720675.
  7. Kurjak, A; Stanojevic, M; Andonotopo, W; Salihagic-Kadic, A; Carrera, JM; Azumendi, G (2004). "Behavioral pattern continuity from prenatal to postnatal life--a study by four-dimensional (4D) ultrasonography". Journal of Perinatal Medicine. 32 (4): 346–53. doi:10.1515/JPM.2004.065. PMID 15346822. S2CID 44725653.
  8. Lipkin, Paul H. (2009-01-01), Carey, William B.; Crocker, Allen C.; Coleman, William L.; Elias, Ellen Roy (eds.), "Chapter 66 - Motor Development and Dysfunction", Developmental-Behavioral Pediatrics (Fourth Edition), Philadelphia: W.B. Saunders, pp. 643–652, ISBN 978-1-4160-3370-7, retrieved 2021-01-04
  9. Berg, B. (2014-01-01), "Brain Development, Normal Postnatal", in Aminoff, Michael J.; Daroff, Robert B. (eds.), Encyclopedia of the Neurological Sciences (Second Edition), Oxford: Academic Press, pp. 477–480, ISBN 978-0-12-385158-1, retrieved 2021-01-04
  10. Niezgoda, Julie; Bansal, Vipin (2011-01-01), Davis, Peter J.; Cladis, Franklyn P.; Motoyama, Etsuro K. (eds.), "Chapter 2 - Behavioral Development", Smith's Anesthesia for Infants and Children (Eighth Edition), Philadelphia: Mosby, pp. 10–21, ISBN 978-0-323-06612-9, retrieved 2021-01-04
  11. Pouydebat, Emmanuelle; Welser, Kay; Shaw, Erin; Haring, David; Ehmke, Erin; Brewer, David; Wall, Christine E.; Fabre, Anne-Claire; Peckre, Louise (24 November 2016). "Holding-on: co-evolution between infant carrying and grasping behaviour in strepsirrhines". Scientific Reports. 6: 37729. Bibcode:2016NatSR...637729P. doi:10.1038/srep37729. ISSN 2045-2322. PMC 5121892. PMID 27883046.
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