White matter
Corpus callosum
Also called CC, Callosal commissure
The giant bridge of about 200 to 300 million fibers that lets your left and right brain talk.
The corpus callosum is a thick, curved band of white matter that joins the left and right halves of the brain. It holds roughly 200 to 300 million nerve fibers, making it the biggest cable in the brain. It lets both halves share what they see, feel, and plan, so you experience one world instead of two.
Where it is
Deep in the middle of the brain, at the bottom of the long groove between the two halves. If you gently parted the halves, it is the pale arch you would find underneath. It forms the roof of the fluid-filled spaces called the lateral ventricles.
What it does
Sharing the senses
Each half of the brain sees and feels the opposite side of the world. The corpus callosum stitches the two halves into one seamless picture.
Two-handed tasks
It helps both hands work together, like when you tie shoelaces, play the piano, or clap.
Putting words to things
In most people, language lives mainly on the left. The corpus callosum lets the left side name and talk about things the right side notices.
Front to back
Its front part links the two frontal lobes, while its thick back end, the splenium, links the visual areas.
Think of it as a huge bridge between two cities, carrying a constant stream of traffic so each side always knows what the other is doing.
Works with
- Cingulate cortexThis curved strip of cortex lies right on top of the corpus callosum, hugging it along its whole length.
- CingulumThis belt of fibers runs just above it, inside the cingulate cortex.
- Lateral ventriclesIts underside forms the roof of these fluid-filled spaces.
- FornixThis memory pathway hangs just below it, joined by a thin sheet of tissue.
- Frontal lobeIts front fibers link the left and right planning areas so both sides pursue the same goal.
- Occipital lobeIts back fibers join the two halves of your view, so there is no seam down the middle of what you see.
When it goes wrong
Split-brain surgery
To stop severe seizures spreading from one side to the other, surgeons have sometimes cut the corpus callosum. Patients usually seem remarkably normal in daily life, but careful tests show each half can act on its own.
Born without one
Some people are born without a corpus callosum, a condition called agenesis. Effects range from mild to severe, depending on whether other brain conditions are present too.
Alien hand
Rarely, damage here causes "alien hand" syndrome, where one hand seems to act on its own.
For learning only, not medical advice. If you have a health concern, talk to a doctor.
Surprising facts
- Roger Sperry won a share of the 1981 Nobel Prize for split-brain studies. When an object was shown only to the right half of the brain, patients could not name it, yet their left hand could pick it out by touch.
- It is mostly formed by age 4, but it keeps growing slowly into your twenties.
By the numbers
Where the name comes from
Latin for "tough body". Callosum is related to "callus", the hard skin on your hands.
Learn it in a lesson
- Wiring and fluidWhite matter cables and the ventricles. A short guided lesson in 3D.
Quick quiz
3 questions. Your answers are saved and come back in your daily review.
Which of these is a job of the corpus callosum?
Show the answer
Sharing the senses. Each half of the brain sees and feels the opposite side of the world. The corpus callosum stitches the two halves into one seamless picture.
Sharing the senses. Each half of the brain sees and feels the opposite side of the world. The corpus callosum stitches the two halves into one seamless picture.
The corpus callosum is part of which larger structure?
Show the answer
White matter pathways. It belongs to the white matter pathways.
White matter pathways. It belongs to the white matter pathways.
Which part fits this description? "Like a huge bridge between two cities, carrying a constant stream of traffic so each side always knows what the other is doing."
Show the answer
Corpus callosum. It is the corpus callosum. The giant bridge of about 200 to 300 million fibers that lets your left and right brain talk.
Corpus callosum. It is the corpus callosum. The giant bridge of about 200 to 300 million fibers that lets your left and right brain talk.
These parts now come back in your daily review, just before you would forget them.
Practice it and its neighbors in 3DSources
- Neuroanatomy, Corpus Callosum, StatPearls, NCBI Bookshelf
- Corpus callosum, Queensland Brain Institute, University of Queensland
- The Nobel Prize in Physiology or Medicine 1981: Press release, NobelPrize.org
Spotted a mistake? Tell us.
Explore the corpus callosum in 3D
Turn it around, zoom inside and see how it connects to the rest of the brain, then test yourself with quick quizzes.
Open it in 3D