Spinal cord Therefore, we become left or right-handed

Right or left-handed? The cause is obviously not in the brain
It has long been believed that it is determined in the brain whether a human is left or right-handed. But now there is evidence that the cause of the handedness is elsewhere - in the spinal cord.

Left-handers have long been forced to write with their right hands
Left-handedness is accepted today as a natural predisposition, but not in all regions of the world. It was different for a long time. In Germany too, left-handers were forced to write with their right-hand hands at school until the 1970s. Such "retraining" can lead to serious problems. To mention here are among other things lack of ability to concentrate, memory and speech disorders. It is believed that it is determined in the brain whether someone is left-handed or right-handed. But now there are new findings.

Whether people become right-handed or left-handed, obviously does not determine the brain, but the spinal cord. German researchers came to this conclusion. (Image: gradt / fotolia.com)

Handedness is not defined in the brain
Whether humans become right-handed or left-handed people is not determined by the brain, but by the spinal cord. Biopsychologists from the Ruhr University Bochum (RUB) come to this conclusion.

As reported by the university in a communication, the Bochum scientists, together with colleagues from the Netherlands and South Africa, have shown that the gene activity in the spinal cord is already asymmetric in the womb. A preference for left or right hand could be due to this asymmetry.

Previously, it was thought that differences in gene activity in the right and left hemispheres could be responsible for the handedness of a human.

A preference for movements of the left or right hand is already formed in the womb from the eighth week of pregnancy, as ultrasound examinations of the 1980s revealed.

From the thirteenth week of pregnancy unborn children suck on either the right or the left thumb.

Cause for the right-left preference rather in the spinal cord
As stated in the communication, arm or hand movements are initiated via the motor cortex in the brain. This sends a corresponding signal to the spinal cord, which converts the command into a movement.

However, the motor cerebral cortex is not connected to the spinal cord from the beginning. Even before the connection is formed, precursors of handedness are visible.

The researchers therefore assumed that the cause of the right-left preference would be more likely to be in the spinal cord than in the brain. That was also suggested by their results.

Differences already in the eighth week of pregnancy
The researchers around private lecturer Sebastian Ocklenburg, Judith Schmitz and Prof. Dr. med. Dr. H. c. Onur Güntürkün found clear right-left differences in gene expression in the spinal cord in the eighth week of pregnancy - and in exactly the Rückenmarkssegementen that control movements of the arms and legs.

From other studies it is known that unborn children make asymmetric hand movements already at this time.

"The results fundamentally change our understanding of the origin of hemispheric asymmetries," conclude the authors. (Ad)