We Finally Know Why Some People Are Left Handed

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Your preference for moving your left or right hand begins in the womb, around the eighth week of pregnancy, according to ultrasound scans.

Previously we had assumed that differences in gene activity of the right and left hemisphere of the brain might be responsible for a person's handedness.

But last year, researchers from Ruhr-Universitat Bochum, who analysed gene expression in the spinal cord during the eighth to the twelfth week of pregnancy, now believe the origins of our hand preference are found in the spinal cord.

Arm and hand movements are started via the motor cortex in the brain, which sends a corresponding signal to the spinal cord. This turns the command to a motion. The motor cortex, however, is not connected to the spinal cord from the beginning - and precursors of a choice of handedness occur before the connections have formed.

This is why researchers now believe our handedness is decided in our spine.


The research, published in February 2017 in the journal eLife and funded by the German Research Foundation, concluded that:

These results fundamentally change our understanding of the cause of hemispheric asymmetries.


The researchers detected marked right-left differences in the eighth week in spinal cord segments that control the movements of arms and legs.

The research results were compiled by a team lead by private lecturer Dr Sebastian Ocklenburg, Judith Schmitz and Prof Dr H. C. Onur Güntürkün.


The team worked with colleagues from the Netherlands and South Africa to attain the results.

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