In rare cases, patients suffering from severe epilepsy undergo an operation in which an entire brain hemisphere is removed. New research shows the startling degree to which the remaining hemisphere is able to pick up the slack.
The new work, co-authored by neuroscientist Dorit Kliemann from the California Institute of Technology, provides insights into how the brain reorganizes itself after a radical loss of brain material. The research is evidence of “compensated cognition,” the scientists write.
The study involved six adults who had undergone a hemispherectomy during childhood in order to reduce epileptic seizures, and six control participants.
The 12 participants were each asked to lie down in a functional magnetic resonance imaging (fMRI) scanner. The scanner measures brain activity by detecting changes associated with blood flow. The technique relies on the fact that cerebral blood flow and neural activity are directly connected – when an area of the brain is in use, blood flow to that region also increases.
The participants were told to try not to fall asleep while the researchers tracked spontaneous brain activity at rest.
The research team examined networks of brain regions known to control processes including those related to vision, movement, emotion, and cognition.
“These results… suggest that between-network interactions may characterize functional reorganization in hemispherectomy,” the authors write in the study. It remains an open question as to how the increased connectivity might assist—or even impair—functioning among hemispherectomy subjects, such as their sociability, motor skills, and decision-making. Future research “will need to investigate the behavioral correlates” of these connections, according to the paper.
The new work is preliminary, and looking ahead, the team would like to expand their research to verify these results among larger sample size, among other improvements to their experimental design.
There’s still so much to learn about the human brain—which is at once incredibly fragile, yet also super resilient.