REAASONS

24/10/2018

The reasons that would be behind being left-handed
The lefties raised their left hand from the 13 of August to celebrate their day and to request that in a majority right-handed society they reduce the difficulties with which they are daily.
Science has tried to identify the causes why for some people the left hand is the only one with which they can execute actions such as writing or grabbing a cup of coffee.
A 2017 investigation concluded that it is possible to determine if someone will be left or right by observing which thumb prefers to suck in the uterus, whether right or left, so the brain has not begun to control the body.
The study entitled The epigenetic regulation of lateralized fetal spinal gene expression underlies the hemispheric asymmetries was carried out by several researchers from German and Dutch institutions, among which are Sebastian Ocklenburg, as principal investigator and Judith Schmitz.
The researchers point out that although this ability does develop in the womb, its cause is not the brain, but the spinal cord. They found that the expression of certain genes in the spinal cord, responsible for controlling the movement of the legs and arms, is different for left-handed and right-handed people.
According to the research published by eLife, "Laterality begins early in the development since coordinated movements of the hand start eight weeks after conception, that is, at 10 weeks gestational age is when 85% of fetuses show more movements of the right arm than the left. "
Which finger did you prefer?
Subsequently, observation of thumb suction in 274 fetuses revealed that at 13 weeks, 90% preferred to suck their right thumb, while only 10% sucked their left thumb.
"The follow-up of 75 infants showed that the preference of thumb sucking correlates significantly with positive dexterity: the 60 children with a preference for the right thumb were right-handed, while of the 15 children with a preference for the left thumb, 10 were left-handed. and 5 right-handed. "
In their study Ocklenburg and Schmitz emphasized that at this stage of development the motor cortex is not functionally linked to the spinal cord, so "it is unlikely that the skill is under the control of the brain" and the asymmetric movements of the hand arise from patterns of spinal activity.
The laterilization
According to the study, a fundamental principle of the organization of the brain is the laterilization, the difference between the left and right hemisphere, not only structural, but also functional.
That difference is present in all vertebrates, and the research says that there are recent studies that speak of their presence also in invertebrates.
The use of the hand, says the study, is the manifestation of the lateralization in humans that has been investigated the most, because "it is related to the organization of cognitive systems in the human brain".