The largest white matter tract in the brain, joining the two cerebral hemispheres
Corpus callosum — about 200 million axons.
Anatomy · Brain & nerves
Corpus callosum
Latin 'tough body'
Brain · cerebral white matter
The largest bundle of nerve fibres in the brain: a thick, curved arch of white matter, roughly 10 cm long, containing some 200 million axons that connect the left and right cerebral hemispheres. It lets the two halves of the brain share information and coordinate. Cutting it to control severe epilepsy produced the famous split-brain studies that won Roger Sperry a Nobel Prize.
How to spot them
- ▸In a midline slice, a thick white C-shaped arch above the fluid-filled chambers and beneath the folded cerebral surface
- ▸Four named parts from front to back: rostrum, genu (knee), body and splenium
- ▸Forms the roof of the lateral ventricles and the floor of the longitudinal fissure
- ▸The curved gyrus lying immediately above it is the cingulate gyrus
What to know
Its Latin name means 'tough body'; its front end is the 'knee' and its thickened rear end the 'pad'
Corpus callosum — genu and splenium.
Surgical division of it to control severe epilepsy led to experiments on 'split-brain' patients
Corpus callosum — corpus callosotomy; Roger Sperry, Nobel Prize 1981.
In a split-brain patient, an object seen only in the left half of the visual field cannot be named aloud
Corpus callosum — the right hemisphere lacks language and cannot pass the information across.
Only placental mammals have one; marsupials and monotremes rely on other, smaller connections
Corpus callosum — marsupials use the anterior commissure.
Sometimes absent from birth, a condition the man who inspired the film Rain Man had
Corpus callosum — agenesis, found in Kim Peek.
Forms the roof of the lateral ventricles, with a thin curved gyrus lying immediately above it
Corpus callosum — the cingulate gyrus arches over it.
Key ideas
- Because sensory and motor pathways cross, each hemisphere sees and controls the opposite side; this bundle lets each half tell the other what it knows.
- Cutting it is a last-resort treatment for epilepsy, stopping seizures from spreading across the two hemispheres.
Quick-fire facts
- •About 10 cm long and containing roughly 200 million axons
- •Parts from front to back: rostrum, genu, body, splenium
- •Its Latin name means 'tough body'
- •Roger Sperry won the 1981 Nobel Prize in Physiology or Medicine for split-brain research, sharing it with David Hubel and Torsten Wiesel
- •Michael Gazzaniga worked with Sperry on the split-brain patients
- •Only placental mammals have a corpus callosum
- •Agenesis of the corpus callosum can be complete or partial and is often discovered incidentally
- •Kim Peek, the 'megasavant' who inspired Rain Man, was born without one
- •It is the roof of the lateral ventricles and lies beneath the cingulate gyrus
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