Brains adapt to loss of one half

As you may have learned in school, brains have two halves, known as hemispheres. Each has various regions that regulate different aspects of our physical and cognitive functioning. The two halves do not work independent of each other, rather they are in constant communication, synchronizing and working in harmony.

One would assume that in people who undergo hemispherectomy, or the removal of one hemisphere, the brain would function a visibly different manner. But new studies show that the remaining hemisphere of the brain learns to adapt and efficiently compensates for the loss of the other half.

Studies were done on six participants in their 20s and early 30s who had undergone hemispherectomy during childhood as a treatment for epileptic seizures.The age at which the hemispherectomy was conducted ranged from 3 months to 11 years old. This difference in period of their operation allowed the scientists to understand how the brain adapts to the loss at different stages.

The team asked the participants who had undergone hemispherectomy — as well as six control participants — to receive functional MRI scans. The scans allowed the researchers to track activity in the brain while it was at rest.

By comparing the brain scans, the team found that the group who had undergone hemispherectomy had stronger brain network connectivity — rather than weaker connectivity, as one might expect — compared with the control group. The regions that the researchers focused on were those that regulate vision, movement, emotion, and cognition.

The people with hemispherectomies were found to be remarkably high functioning. They had intact language skills. It was difficult to discern the difference in participants who had hemispherectomy and those that did not in the control group.

Nevertheless, doctors warn that while it is remarkable that people can live with half a brain, a very small brain lesion, a tumor, or a traumatic brain injury, caused by a biking accident, for example, can have devastating effects on people who have had hemispherectomy.

In the future, the investigators plan to conduct another study to try and replicate the current findings, then to go even further by building an image of how the brain organizes and reorganizes itself to deal with an injury.