Summary: The preference to use one hand over the other is already defined by the 18th week of gestation, a new study reports.
Are you born or do you become right-handed or left-handed? A study led by Valentina Parma, researcher at the International School for Advanced Studies – SISSA of Trieste, and Professor Umberto Castiello of the University of Padua, just published on Scientific Reports, shows that hand preference is already well defined at the 18th week of gestation.
Analysing the characteristics of several foetal movements, the researchers have been able to accurately foresee the motor preference observed in the same boys and girls at age nine. The predictive capacity of the method used seems to be a good starting point for the early recognition of pathologies characterised by cerebral asymmetries, such as depression, schizophrenia and autism spectrum disorders.
It takes a few months for a newborn to be able to grasp an object, a few years to draw and then to write, manifesting the possible preference for the use of one hand or other parts of the body. And yet, a study just published on Scientific Reports shows that as early as in the maternal womb, hand preference is well defined and the motor system is highly sophisticated.
The researchers have studied foetal kinematics to predict manual dominance of 29 foetuses. After nine years they compared their predictions with the preference shown by the same boys and girls obtaining an accuracy that ranged between 89% and 100% depending on the parameters used. In particular, the researchers analysed the movements of the hands of the foetuses at the 14th, 18th and 22nd week of gestation using a 4D ultrasound scan, viewing the three dimensional image in real time and in movement, in 20-minute sessions. They studied three types of movements: two of greater precision, directed to the eyes and mouth, and one directed to the uterine wall, as a control. The results have shown that starting from the 18th week the foetuses execute significantly more quickly the movements requiring precision with that which will become the preferred hand.
The study, conducted by the International School for Advanced Studies – SISSA of Trieste, the Integrated University Hospital of Trieste – ASUITs, Ab.Acus of Milan, the University of Padua and the Lincean Centre Beniamino Segre of Rome, shows the elevated level of maturation and specialisation of the motor system in utero. But not just that. The accuracy of the method used in this study opens new perspectives for its use in the clinical field. Hand preference, in fact, is due to the prevalence of one cerebral hemisphere, the contralateral one, over the other. This characteristic has sometimes been associated to pathologies which involve a cerebral asymmetry, such as depression, schizophrenia and autistic spectrum disorders. Foetal kinematics could be used to identify new markers that would allow to intervene at an early stage and compensate for any development problems.
Source: Chiara Saviane – SISSA
Publisher: Organized by NeuroscienceNews.com.
Image Source: NeuroscienceNews.com image is in the public domain.
Original Research: Full open access research for “The origin of human handedness and its role in pre-birth motor control” by Valentina Parma, Romain Brasselet, Stefania Zoia, Maria Bulgheroni & Umberto Castiello in Scientific Reports. Published online December 1 2017 doi:10.1038/s41598-017-16827-y
The origin of human handedness and its role in pre-birth motor control
The vast majority of humans are right-handed, but how and when this bias emerges during human ontogenesis is still unclear. We propose an approach that explains postnatal handedness starting from 18 gestational weeks using a kinematic analysis of different fetal arm movements recorded during ultrasonography. Based on the hand dominance reported postnatally at age 9, the fetuses were classified as right-handed (86%) or left-handed, in line with population data. We revealed that both right-handed and left-handed fetuses were faster to reach to targets requiring greater precision (i.e., eye and mouth), with their dominant (vs. non-dominant) hand. By using either movement times or deceleration estimates, handedness can be inferred with a classification accuracy ranging from 89 to 100% from gestational week 18. The reliability of this inference hints to the yet unexplored potential of standard ultrasonography to advance our understanding of prenatal life.
“The origin of human handedness and its role in pre-birth motor control” by Valentina Parma, Romain Brasselet, Stefania Zoia, Maria Bulgheroni & Umberto Castiello in Scientific Reports. Published online December 1 2017 doi:10.1038/s41598-017-16827-y