Introductionbrain are connected by a thick bundle of nerve fibres called the Corpus Callosum that ensures both sides of the brain can communicate and send signals to each other.
- A combination of sensory, motor and cognitive information is constantly being transferred between hemispheres via this neural highway.
- There are approximately 300 million axons (nerve fibres) in an average corpus callosum. It is located in the white matter of the cerebrum and is around 10cm long at the midline. This neural bridge is the largest white matter structure in the brain and only evolved in placental mammals.
- If the corpus callosum is severed, the brain’s hemispheres are not able to communicate properly, and the loss of a range of functions can occur eg. changes to visual perception, speech and memory. Surgical severing of the corpus callosum is a last-resort method for untreatable epilepsy, to stop seizures spreading across the brain.
Agenesis of the Corpus Callosum
Agenesis of the corpus callosum (AgCC) is a condition in which an individual is born with a partial corpus callosum or no corpus callosum at all.
- The corpus callosum typically develops between 12 and 20 weeks and continues to experience structural changes even into adulthood.
- AgCC can be caused by a number of factors including chromosome mutations, prenatal infections, exposure of the fetus to certain toxins or medications, and abnormal brain development due to cysts
- Most doctors recommend periodic check-ups by specialists in pediatrics and neurology to monitor associated conditions like seizure disorder or hydrocephaly (a build up of fluid in brain). Associated disorders such as seizures, hydrocephaly, mental retardation and/or spasticity may require treatment with medication, shunting, special rehabilitation, and/or physical therapy.
- Most children do not die because of the absence of the corpus callosum, and if they do experience mental retardation, it is usually non-progressive.
Image 2: Fiber tracts from six segments of the corpus callosum providing interhemispheric linkage between specific cortical regions. The six segments and their fibers are identified as genu (coral), premotor (green), sensory-motor (purple), parietal (pink), temporal (yellow), and splenium (blue).
Left or Right Dominant
Being left-brained or right-brained often pops up in popular culture. "Left-brainers” are complimented on their logical approach, and right-brained is synonymous with being creative/emotive. But although the notion of “hemisphericity” has captured the popular imagination, it is not supported by neuroscientific research. In a normal brain, the left and right sides are connected by the corpus callosum. Information transfer across the corpus callosum is extremely efficient. A picture shown to just the right brain (easily done using computer-based techniques) transmits that information to the left brain within 20 milliseconds. The corpus callosum allows virtually instant communication between the two halves of a normal brain. This means the whole brain is involved in processing, no matter how analytic or artistic the task.
- New neuroscience techniques eg Diffusion Tensor Imaging (DTI), have been specifically designed to show connections between different regions of the brain. Research using such techniques indicates that both sides of your brain are involved in everything we do.
- When working on trigonometry, playing the ukulele, or taking part in “right-brain” training, both ther left and right brain are simultaneously processing and integrating information.
Image 3: Split Brain experiments
The Einstein Connection.
Fantastic connections between the right and left hemispheres of Albert Einstein’s brain may have contributed to his intelligence. Researchers examined images of Einstein’s corpus callosum and found this area was unusually well connected compared to other people.Their findings show that Einstein had more extensive connections between certain parts of his cerebral hemispheres compared to both younger and older control groups.
- Qld Brain Inst. Corpus Callosum Available from:https://qbi.uq.edu.au/brain/brain-anatomy/corpus-callosum (accessed 31.12.2020)
- Thought Co. CC Available from:https://www.thoughtco.com/corpus-callosum-anatomy-373219 (accessed 1.1.2021)
- Birth defect registry Agnesis of the CC Available from:https://birthdefects.org/agenesis-of-corpus-callosum/ (accessed 1.1.2021)
- The Conversation Monday’s medical myth: you can selectively train your left or right brain Available from: https://theconversation.com/mondays-medical-myth-you-can-selectively-train-your-left-or-right-brain-4704(accessed 1.1.2021)
- Men W, Falk D, Sun T, Chen W, Li J, Yin D, Zang L, Fan M. The corpus callosum of Albert Einstein‘s brain: another clue to his high intelligence?. Brain. 2014 Apr 1;137(4):e268-.Available from:https://academic.oup.com/brain/article/137/4/e268/365419 (accessed 1.1.2021)