Hindawi Publishing Corporation International Journal of Pediatrics Volume 2012, Article ID 191562, 10 pages doi:10.1155/2012/191562 Review Article The Grasp Reﬂex and Moro Reﬂex in Infants: Hierarchy of Primitive Reﬂex Responses Yasuyuki Futagi, Yasuhisa Toribe, and Yasuhiro Suzuki Department of Pediatric Neurology, Osaka Medical Center and Research Institute for Maternal and Child Health, 840 Murodo-cho, Izumi, Osaka 594-1101, Japan Correspondence should be addressed to Yasuyuki Futagi, jqfkk025@yahoo.co.jp Received 27 October 2011; Accepted 30 March 2012 Academic Editor: Sheﬀali Gulati Copyright © 2012 Yasuyuki Futagi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The plantar grasp reﬂex is of great clinical signiﬁcance, especially in terms of the detection of spasticity. The palmar grasp reﬂex also has diagnostic signiﬁcance. This grasp reﬂex of the hands and feet is mediated by a spinal reﬂex mechanism, which appears to be under the regulatory control of nonprimary motor areas through the spinal interneurons. This reﬂex in human infants can be regarded as a rudiment of phylogenetic function. The absence of the Moro reﬂex during the neonatal period and early infancy is highly diagnostic, indicating a variety of compromised conditions. The center of the reﬂex is probably in the lower region of the pons to the medulla. The phylogenetic meaning of the reﬂex remains unclear. However, the hierarchical interrelation among these primitive reﬂexes seems to be essential for the arboreal life of monkey newborns, and the possible role of the Moro reﬂex in these newborns was discussed in relation to the interrelationship. 1. Introduction Both the palmar grasp reﬂex and the plantar grasp reﬂex are very primitive in the sense that they can be elicited in all normal preterm infants at as early as 25 weeks of postconceptional age (PCA) [1]. During routine ultrasound examination, fetal palmar reﬂex grasping of the umbilical cord has been repeatedly observed, which ﬁrst appears at 16 weeks’ gestation [2–4]. These grasp reﬂexes are easy to elicit but have been proved to be of distinctive clinical signiﬁcance for the early detection of infants with neurodevelopmental abnormalities [5–8]. The Moro reﬂex was ﬁrst described by Ernst Moro in 1918 [9]. This reﬂex is also primitive, being seen in some preterm infants at 25 weeks of PCA and in the majority by 30 weeks of PCA [1]. Since his report, many authors have devised a variety of methods for eliciting the reﬂex, and the underlying neural mechanism including aﬀerent pathways of the reﬂex has been a subject of considerable discussion [10– 13]. The phylogenetic meaning of this reﬂex also remains unclear [9, 10]. It is interesting that, in spite of the great diﬀerence in the motor behavior, there is a close interrelationship between these primitive reﬂexes in the responses: the palmar grasp reﬂex inhibits the Moro reﬂex [12, 14–17]. This paper mainly concerns the clinical signiﬁcance and neural mechanism of the grasp reﬂex and the Moro reﬂex and also attempts to discuss the meaning of these reﬂexes based on comparison of the responses in human infants with those in monkey infants and the hierarchical interrelation of the responses of the primitive reﬂexes. 2. The Grasp Reﬂex 2.1. Elicitation. To elicit the palmar grasp reﬂex, the exam- iner inserts his or her index ﬁnger into the palm of the infant from the ulnar side and applies light pressure to the palm, with the infant lying on a ﬂat surface in the symmet- rical supine position while awake [18–20]. Tactile without pressure and nociceptive stimulation of the palm are both inadequate. The response of the reﬂex comprises ﬂexion of