There is a relatively left-biased grasp-reflex asymmetry in human newborns with familial sinistrality compared to those without familial sinistrality.
Grasp-reflex asymmetry was studied in human newborns with regard to familial sinistrality (FS). In the total sample, the following results were obtained. The mean grasp-reflex strength from the right hand was found to be significantly greater than that from the left hand in FS- subjects. There was no significant difference between these parameters in FS+ subjects. The mean right minus left (R-L) reflex strength was significantly greater than zero in FS- subjects. The mean R-L reflex did not significantly differ from zero in FS+ subjects. The mean reflex strength from the right hand was found to be significantly greater in FS- subjects than FS+ subjects. There was no significant difference between the mean reflex strengths from the left hands of the FS- and FS+ subjects. The mean R-L reflex in subjects FS- was found to be significantly greater than that in FS+ subjects. Similar results were obtained from the male and female subjects. It was concluded that FS is an important factor determining the degree of the grasp-reflex asymmetry in newborns. The relatively left-biased grasp-reflex asymmetry under the influence of FS indicates a genetic origin of the motor asymmetry in newborns. This, in turn, suggests that cerebral lateralization inducing manual asymmetry in humans may have been preprogrammed genetically.
Tan
U
U
Atatürk University, Medical Faculty, Department of Physiology, Erzurum, Turkey.
Ors
R
R
Kürkçüoglu
M
M
Kutlu
N
N
Cankaya
A
A
D005260:Female; D007839:Functional Laterality / Q000235:genetics*; D006225:Hand; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D009048:Motor Skills; D012018:Reflex / Q000235:genetics*; D012737:Sex Factors