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Sepa por qué es zurdo (o diestro)
04/03/2020
Know why you are left handed (or right handed)
The brain has nothing to do with history, as previously thought. The culprit that we write with one hand or another hand is the spinal cord
• ESTHER MUCIENTES
• @emucient
Not long ago in Spain being left-handed was a stigma. "In the school they tied my left hand to my back so that I could write with my right," says María del Carmen, 61, now ambidextrous, "although my head always pulls on to do everything with the left." Luckily, today, being left-handed or right-handed is no problem, unless they sit side by side at lunchtime. In that case, the crash is assured.
At present, 15% of the population is left-handed, 1% ambidextrous and the rest right-handed. What makes such a difference? Why are there more right-handed than left-handed? What determines it? Until recently it was believed that the decision to use the left or the right was something that was determined by our brain. Exactly, due to differences in the biological activity of the right and left hemisphere.
The belief was, therefore, that if the baby matured before the right hemisphere that the left would be right-handed, and vice versa. That is, it was our brain that decided if you would get up from a chair on the left side or if you would take the knife with your right hand. Well, it's not like that. The brain is not guilty. So?
According to an investigation by the German University 'Ruhr de Bochum', published in the magazine 'eLife' and led by scientists Sebastian Ocklenburg and Judith Smith, the culprit that we write with one hand or the other is the spinal cord.
The study has shown that babies already show considerable asymmetries in arm movements even before the motor cortex is functionally linked to the spinal cord. In plain language: the activity in the spinal cord is asymmetric, that is, it lacks symmetry already in the uterus.
The researchers decided to study "the preference to use one hand or another in the womb from the eighth week of pregnancy", since it has been known since the 1980s that the fetus uses one side or other.
The investigation, carried out in 274 babies, revealed that at 13 weeks gestation 90% of them sucked their right thumb, while only 10% did so with their left. Once they were born, 75 of them were followed up and discovered that, of those who sucked their right thumbs in the womb, 60 continued to do so and 15 preferred the left one; five used the right one in their mother's gut and 10 the left one.
A fact that shows that it is "unlikely" that the brain will guide the choice of one thumb or another and that it comes from the activity patterns of the spine. "It is likely that the spine represents the molecular basis of laterality," says the study.
The researchers concluded, therefore, that the expression of certain genes found in the bone marrow, and that are those that control limb movements, is different in left-handed and right-handed from the eighth week of pregnancy .
Since communication between the brain and the spinal cord does not occur until after the 15th week of pregnancy, the only way for a baby to suck the right thumb and not the left, or vice versa, resides in the spinal cord, which It is who determines whether we are right or left handed. And since in those weeks of gestation there is no connection between the brain and the medulla, only this can determine whether we will write with one or the other hand.
ENVIRONMENTAL FACTORS
However, this does not explain why we prefer, even being nothing more than a fetus, one side or the other. Researchers have concluded that this preference is due to environmental factors that occur during pregnancy. It is not determined by DNA, as it was believed, but by what is known as epigenetics, the doctrine according to which the features that characterize a living being are configured when it is being developed. In short, external stimuli that influence the development of a person.
To try to determine these factors, the researchers analyzed the way in which enzymes were grouped in infants, their feeding or DNA interactions, discovering that all this, and probably many more things yet to be determined, directly influence why we use more The right hand than the left.
"While our findings suggest that a large part of these factors that influence the preference for the right or left before birth, there are still several important perinatal and postnatal environmental factors, such as social modulation, that shape the real laterality ", notes the study, which concludes that we are left-handed or right-handed" both by genetic factors, "that is, by our spinal cord," and by the epigenét
The brain has nothing to do with history, as previously thought. The culprit that we write with one hand or another hand is the spinal cord
• ESTHER MUCIENTES
• @emucient
Not long ago in Spain being left-handed was a stigma. "In the school they tied my left hand to my back so that I could write with my right," says María del Carmen, 61, now ambidextrous, "although my head always pulls on to do everything with the left." Luckily, today, being left-handed or right-handed is no problem, unless they sit side by side at lunchtime. In that case, the crash is assured.
At present, 15% of the population is left-handed, 1% ambidextrous and the rest right-handed. What makes such a difference? Why are there more right-handed than left-handed? What determines it? Until recently it was believed that the decision to use the left or the right was something that was determined by our brain. Exactly, due to differences in the biological activity of the right and left hemisphere.
The belief was, therefore, that if the baby matured before the right hemisphere that the left would be right-handed, and vice versa. That is, it was our brain that decided if you would get up from a chair on the left side or if you would take the knife with your right hand. Well, it's not like that. The brain is not guilty. So?
According to an investigation by the German University 'Ruhr de Bochum', published in the magazine 'eLife' and led by scientists Sebastian Ocklenburg and Judith Smith, the culprit that we write with one hand or the other is the spinal cord.
The study has shown that babies already show considerable asymmetries in arm movements even before the motor cortex is functionally linked to the spinal cord. In plain language: the activity in the spinal cord is asymmetric, that is, it lacks symmetry already in the uterus.
The researchers decided to study "the preference to use one hand or another in the womb from the eighth week of pregnancy", since it has been known since the 1980s that the fetus uses one side or other.
The investigation, carried out in 274 babies, revealed that at 13 weeks gestation 90% of them sucked their right thumb, while only 10% did so with their left. Once they were born, 75 of them were followed up and discovered that, of those who sucked their right thumbs in the womb, 60 continued to do so and 15 preferred the left one; five used the right one in their mother's gut and 10 the left one.
A fact that shows that it is "unlikely" that the brain will guide the choice of one thumb or another and that it comes from the activity patterns of the spine. "It is likely that the spine represents the molecular basis of laterality," says the study.
The researchers concluded, therefore, that the expression of certain genes found in the bone marrow, and that are those that control limb movements, is different in left-handed and right-handed from the eighth week of pregnancy .
Since communication between the brain and the spinal cord does not occur until after the 15th week of pregnancy, the only way for a baby to suck the right thumb and not the left, or vice versa, resides in the spinal cord, which It is who determines whether we are right or left handed. And since in those weeks of gestation there is no connection between the brain and the medulla, only this can determine whether we will write with one or the other hand.
ENVIRONMENTAL FACTORS
However, this does not explain why we prefer, even being nothing more than a fetus, one side or the other. Researchers have concluded that this preference is due to environmental factors that occur during pregnancy. It is not determined by DNA, as it was believed, but by what is known as epigenetics, the doctrine according to which the features that characterize a living being are configured when it is being developed. In short, external stimuli that influence the development of a person.
To try to determine these factors, the researchers analyzed the way in which enzymes were grouped in infants, their feeding or DNA interactions, discovering that all this, and probably many more things yet to be determined, directly influence why we use more The right hand than the left.
"While our findings suggest that a large part of these factors that influence the preference for the right or left before birth, there are still several important perinatal and postnatal environmental factors, such as social modulation, that shape the real laterality ", notes the study, which concludes that we are left-handed or right-handed" both by genetic factors, "that is, by our spinal cord," and by the epigenét
