View source for Biology:Palmar grasp reflex

{{Short description|Primitive and involuntary reflex}}
[[File:Grasp reflex baby.jpg|thumb|350x350px|Infant grasping adult finger]]
The '''palmar grasp reflex''' (or '''grasp reflex''') is a [[Biology:Primitive reflexes|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.<ref name=":0">{{Citation|last1=Swaiman|first1=Kenneth F.|title=3 - Neurologic Examination after the Newborn Period Until 2 Years of Age|date=2017-01-01|url=http://www.sciencedirect.com/science/article/pii/B9780323371018000035|work=Swaiman's Pediatric Neurology (Sixth Edition)|pages=14–19|editor-last=Swaiman|editor-first=Kenneth F.|publisher=Elsevier|language=en|isbn=978-0-323-37101-8|access-date=2021-01-04|last2=Phillips|first2=John|editor2-last=Ashwal|editor2-first=Stephen|editor3-last=Ferriero|editor3-first=Donna M.|editor4-last=Schor|editor4-first=Nina F.}}</ref> Placement of the object triggers a [[Biology:Stretch reflex|spinal reflex]], resulting from stimulation of tendons in the palm, that gets transmitted through motor neurons in the median and ulnar [[Biology:Sensory nerve|sensory nerve]]s.<ref name=":3">{{Citation|last1=Anekar|first1=Aabha A.|title=Palmar Grasp Reflex|date=2021|url=http://www.ncbi.nlm.nih.gov/books/NBK553133/|work=StatPearls|place=Treasure Island (FL)|publisher=StatPearls Publishing|pmid=31985926|access-date=2021-10-28|last2=Bordoni|first2=Bruno}}</ref><ref name=":2" /> The reverse motion can be induced by stroking the back or side of the hand.<ref name=":2">{{cite journal|last1=Futagi|first1=Yasuyuki|last2=Toribe|first2=Yasuhisa|last3=Suzuki|first3=Yasuhiro|title=The Grasp Reflex and Moro Reflex in Infants: Hierarchy of Primitive Reflex Responses|journal=International Journal of Pediatrics|date=2012|volume=2012|pages=191562|doi=10.1155/2012/191562|pmid=22778756|pmc=3384944|doi-access=free }}</ref>
A [[Biology:Fetus|fetus]] exhibits the reflex ''in utero'' by 28 weeks into gestation (sometimes, as early as 16 weeks<ref>{{cite journal|last1=Sherer|first1=DM|date=June 1993|title=Fetal grasping at 16 weeks' gestation.|journal=Journal of Ultrasound in Medicine|volume=12|issue=6|pages=316|doi=10.7863/jum.1993.12.6.316|pmid=8515527|s2cid=21202088 |doi-access=}}</ref>),<ref>{{cite journal|last1=Jakobovits|first1=AA|date=2009|title=Grasping activity in utero: a significant indicator of fetal behavior (the role of the grasping reflex in fetal ethology).|journal=Journal of Perinatal Medicine|volume=37|issue=5|pages=571–2|doi=10.1515/JPM.2009.094|pmid=19492927|s2cid=26736429}}</ref><ref>{{cite journal|last1=Jakobovits|first1=A|date=2 September 2007|title=[Grasping reflex activity in utero is one element of fetal behavior (Grasping activity is a part of fetal ethology)].|journal=Orvosi Hetilap|language=Hungarian|volume=148|issue=35|pages=1673–5|doi=10.1556/OH.2007.28089|pmid=17720675}}</ref><ref>{{cite journal|last1=Kurjak|first1=A|last2=Stanojevic|first2=M|last3=Andonotopo|first3=W|last4=Salihagic-Kadic|first4=A|last5=Carrera|first5=JM|last6=Azumendi|first6=G|date=2004|title=Behavioral pattern continuity from prenatal to postnatal life--a study by four-dimensional (4D) ultrasonography.|journal=Journal of Perinatal Medicine|volume=32|issue=4|pages=346–53|doi=10.1515/JPM.2004.065|pmid=15346822|s2cid=44725653}}</ref> and persists until development of rudimentary [[Engineering:Fine motor skill|fine motor skill]]s between two and six months of age.<ref name=":0" /><ref>{{Citation|last=Lipkin|first=Paul H.|title=Chapter 66 - Motor Development and Dysfunction|date=2009-01-01|url=http://www.sciencedirect.com/science/article/pii/B9781416033707000663|work=Developmental-Behavioral Pediatrics (Fourth Edition)|pages=643–652|editor-last=Carey|editor-first=William B.|place=Philadelphia|publisher=W.B. Saunders|language=en|isbn=978-1-4160-3370-7|access-date=2021-01-04|editor2-last=Crocker|editor2-first=Allen C.|editor3-last=Coleman|editor3-first=William L.|editor4-last=Elias|editor4-first=Ellen Roy}}</ref><ref>{{Citation|last=Berg|first=B.|title=Brain Development, Normal Postnatal|date=2014-01-01|url=http://www.sciencedirect.com/science/article/pii/B9780123851574010320|encyclopedia=Encyclopedia of the Neurological Sciences (Second Edition)|pages=477–480|editor-last=Aminoff|editor-first=Michael J.|place=Oxford|publisher=Academic Press|language=en|isbn=978-0-12-385158-1|access-date=2021-01-04|editor2-last=Daroff|editor2-first=Robert B.}}</ref><ref name=":1">{{Citation|last1=Niezgoda|first1=Julie|title=Chapter 2 - Behavioral Development|date=2011-01-01|url=http://www.sciencedirect.com/science/article/pii/B978032306612900002X|work=Smith's Anesthesia for Infants and Children (Eighth Edition)|pages=10–21|editor-last=Davis|editor-first=Peter J.|place=Philadelphia|publisher=Mosby|language=en|isbn=978-0-323-06612-9|access-date=2021-01-04|last2=Bansal|first2=Vipin|editor2-last=Cladis|editor2-first=Franklyn P.|editor3-last=Motoyama|editor3-first=Etsuro K.}}</ref>

==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 [[Biology:Vestigiality|vestigial]] in humans and in other non-fur carrying primates.<ref>{{cite journal |last1=Pouydebat |first1=Emmanuelle |last2=Welser |first2=Kay |last3=Shaw |first3=Erin |last4=Haring |first4=David |last5=Ehmke |first5=Erin |last6=Brewer |first6=David |last7=Wall |first7=Christine E. |last8=Fabre |first8=Anne-Claire |last9=Peckre |first9=Louise |title=Holding-on: co-evolution between infant carrying and grasping behaviour in strepsirrhines |journal=Scientific Reports |date=24 November 2016 |volume=6 |pages=37729 |doi=10.1038/srep37729 |pmid=27883046 |language=en |issn=2045-2322|pmc=5121892 |bibcode=2016NatSR...637729P }}</ref> 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.<ref name=":3" />

== Clinical significance ==
In humans, absence of the palmar grasp reflex or persistence of the reflex can both be indicators of [[Biology:Development of the nervous system|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.<ref name=":2" /> Based on collected evidence, there is no significant difference between the reflexes of normal-term and pre-term infants.<ref name=":3" /><ref name=":2" />

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.<ref name=":2" /> Absence of the grasp reflex could also be an indicator of [[Medicine:Nerve injury|peripheral nerve injury]] or injury to the spinal cord.<ref name=":3" /> Persistence of the grasp reflex could be an indication of brain [[Medicine:Lesion|lesion]]s or [[Medicine:Cerebral palsy|cerebral palsy]].<ref name=":3" /><ref name=":2" /> Presence of the reflex in infants older than four months could be an indicator of damage to the [[Biology:Central nervous system|central nervous system]]. This damage could be a result of neural degeneration, lack of oxygen in the brain, or other genetic factors.{{cn|date=November 2021}} 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.<ref name=":3" />

==References==
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{{Reflex}}

[[Category:Reflexes]]

{{Sourceattribution|Palmar grasp reflex}}