Region · Volume I
The Corpus Callosum
The bridge that lets two half-brains think as one.
Hidden deep in the middle of the brain, the corpus callosum is a thick cable of roughly 200 million nerve fibers connecting the left and right hemispheres. Everything one side learns, it shares across this bridge in milliseconds.
What it does
- Carrying signals between the left and right hemispheres
- Coordinating two-handed movement
- Sharing vision from each half of the visual field
- Linking language on the left with emotion and tone on the right
Go deeper
Structures inside the corpus callosum
In the real world
Why does this matter?
Split-brain surgery
In severe epilepsy, surgeons once cut the corpus callosum to stop seizures spreading. Studying those patients won Roger Sperry a Nobel Prize and revealed that each hemisphere has its own style of thinking.
Reading development
Callosal fibers thicken through childhood as kids learn to read and write, which is why brain imaging of white matter now helps identify dyslexia early.
Diagnosing multiple sclerosis
MS attacks the fatty myelin that insulates white matter. Thinning of the corpus callosum on MRI is one of the earliest signs doctors look for.