Why we are left-handed or right-handed? According to new scientific research, it would not be the brain, but the spinal cord, which would determine that we use the left or right preferably.
Until now, we had assumed that it was the Brain – the asymmetries or differences in the gene activity of the right hemisphere and the left hemisphere – that determined that we were right-handed or left-handed. But According to a recent study, such responsibility could fall on a spinal card.
The research led by Sebastian Ocklenburg, Judith Schmitz and Onur Güntürkün, from the German University Ruhr in Bochum, would point out that the gene activity in the spinal cord is asymmetric already in the uterus, and the preference for the right or left hand can be traced back to that asymmetry. “These results fundamentally change our understanding of the cause of hemispheric asymmetries,” explain the authors, who have published their study in the eLife journal.
The movements of arms and hands are initiated through the motor cortex in the brain, which sends a signal to the spinal cord and this, in turn, converts the order into a movement. However, the motor cortex is not connected to the spinal cord from the beginning, and since, even before these forms of connection, there seems to be a predilection for the left or the right, the researchers believe that the cause of that preference should be rooted in the spinal cord instead of in the brain.
These scientists studied the gene expression in the spinal cord from the eighth to the twelfth week of and, already in the eighth, found marked differences in the right part and the left part, precisely in those segments of the spinal cord that control the movements of arms and legs. Other research had also previously pointed out that the preferred use of the right hand or the left hand is something that develops in the maternal womb after that eighth week of gestation.