Saturday, February 11, 2017

Fact of the day: Handedness arises from genes in the spinal cord

Handedness is an asymmetry arising due to left-right differences in the development of nervous system. Evidences suggest that a human embryo of eight weeks is able to move its right arm more than the left arm.

Well, if you know something about neurologic development in-utero, you must know that at eight weeks signals are not transmitted from the brain yet. Instead the signals travel from the spinal cord.

The left side of the cord matures faster than the right cord. This means the genes that control growth and development are activated faster on the left cord than the right one. In the hindbrain, it is the other way around.

That's all
- Jaskunwar Singh


  1. Good info Singh. Any reference?
    Going by this fact, not sure why hand dominance is considered abnormal in kids less than 1 yr. Any explanation?

  2. Reference:

    Babies don't usually show dominance of one hand (left or right) before 2-3 years of age. An infant tries to hold a toy with both hands, so specific dominance on one side cannot be determined.
    If in case dominance is shown before 18 months of age, it might signal a motor problem due to injuries in the contralateral part of brain, and so needs a proper clinical evaluation.


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