Until now, we had assumed that it was the brain – the asymmetries or differences in the gene activity of the right and left hemispheres – that determined whether we were left-handed or right-handed, but according to a recent study this responsibility could fall on the spinal cord .
This research, led by Sebastian Ocklenburg, Judith Schmitz – both in the image above – and Onur Güntürkün, from the German Ruhr University of Bochum, would point out that the gene activity in the spinal cord is asymmetric already in the uterus, and the Right or left hand preference 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 journal eLife .
Arm and hand movements are initiated through the motor cortex in the brain, which sends a signal to the spinal cord, which in turn converts the command into movement. However, the motor cortex is not connected to the spinal cord from the beginning , and since, even before these forms of connection, there appears to be a predilection for either the left or the right, the researchers believe that the cause of that preference must be of being rooted in the spinal cord rather than in the brain.
These scientists studied gene expression in the spinal cord from the eighth to the twelfth week of pregnancy and, already in the eighth, they found marked differences in the right and left part, precisely in those segments of the spinal cord that control movements of arms and legs. Other research had also previously pointed out that the preferential use of the right or left hand is something that develops in the womb from the eighth week of gestation.
Image: © RUB, Marquard
