Caltech neuroscientists find normal brain communication in people who lack connections between right and left hemispheres
Like a bridge that spans a river to connect two major metropolises, the corpus callosum is the main conduit for information flowing between the left and right hemispheres of our brains. Now, neuroscientists at the California Institute of Technology (Caltech) have found that people who are born without that link-a condition called agenesis of the corpus callosum, or AgCC-still show remarkably normal communication across the gap between the two halves of their brains.
Their findings are outlined in a paper published October 19 in The Journal of Neuroscience.
Our brains are never truly at rest. Even when we daydream, there is a tremendous amount of communication happening between different areas in the brain. According to J. Michael Tyszka, lead author on the Journal of Neuroscience paper and associate director of the Caltech Brain Imaging Center, many areas of the brain display slowly varying patterns of activity that are similar to one another. The fact that these areas are synchronized has led many scientists to presume that they are all part of an interconnected network called a resting-state network. Much to their surprise, Tyszka and his team found that these resting-state networks look essentially normal in people with AgCC, despite the lack of connectivity.
"This was a real surprise," says Tyszka. "We expected to see a lot less coupling between the left and right brain in this group-after all, they are missing about 200 million connections that would normally be there. How do they manage to have normal communication between the left and right sides of the brain without the corpus callosum?"
The work used functional magnetic resonance imaging (fMRI) to demonstrate that synchronized activity between the left and right brain survives even this sort of radical rewiring of the nerve connections between the two hemispheres. The presence of symmetric patterns of activity in individuals born without a corpus callosum highlights the brain's remarkable plasticity and ability to compensate, says coauthor Lynn Paul, research staff member and lecturer in psychology at Caltech. "It develops these fundamental networks even when the left and right hemispheres are structurally disconnected."