People with half a brain. Literally.

For some children with severe epilepsy, the best treatment may be a very rare surgical procedure in which a large portion -- even half -- of the child's brain is removed or disconnected. Amazingly, many of these individuals can relearn motor, language, and cognitive skills. How? The brain reorganizes itself and builds new connections. To better understand this incredible process, and hopefully inform new interventions and rehabilitation, Caltech neuroscientists conducted brain scans on six adults "all of whom received the surgeries as children and now have relatively normal cognitive abilities." From Caltech:

"Despite missing an entire brain hemisphere, we found all the same major brain networks that you find in healthy brains with two hemispheres," says Dorit Kliemann, lead author of the new report and a postdoctoral scholar who works in the laboratory of Ralph Adolphs (PhD '93), the Bren Professor of Psychology, Neuroscience, and Biology, and the director of the Caltech Brain Imaging Center.

The brain scans also revealed an increased number of connections between the brain networks in the patients compared to healthy individuals. For example, the regions in the patients' brains that control the function of walking appeared to be communicating more with the regions that control talking than what is typically observed.

"It appears that the networks are collaborating more," says Kliemann. "The networks themselves do not look abnormal in these patients, but the level of connections between the networks is increased in all six patients...."

Says Kliemann, "It's truly amazing what these patients can do. Yes, they have challenges, but their cognitive abilities are still remarkably high functioning given that they are missing half of the brain tissue. We need to understand how this is possible with only a single brain hemisphere—an important question about plasticity, reorganization, and compensation."

"Patients Missing One Brain Hemisphere Show Surprisingly Intact Neural Connections" (Caltech)

"Intrinsic Functional Connectivity of the Brain in Adults with a Single Cerebral Hemisphere" (Cell Report)