Ein abgetrenntes Gehirn offenbart die Fähigkeit, Kommunikation umzuleiten | Forscher fanden heraus, dass ein winziger Bruchteil der verbleibenden Nervenfasern ausreicht, um ein nahezu normales Maß an integrierter Gehirnfunktion aufrechtzuerhalten, und weisen auf ein immenses Potenzial für die Reorganisation nach einer Verletzung hin.

From the article: A new study reveals the human brain’s remarkable ability to maintain communication between its two hemispheres even when the primary connection is almost entirely severed. Researchers discovered that a tiny fraction of remaining nerve fibers is sufficient to sustain near-normal levels of integrated brain function, a finding [published](https://www.pnas.org/doi/10.1073/pnas.2520190122) in the Proceedings of the National Academy of Sciences. This observation challenges long-held ideas about how the brain is wired and suggests an immense potential for reorganization after injury.

The brain’s left and right hemispheres are linked by the corpus callosum, a massive bundle of about 200 million nerve fibers that acts as a superhighway for information. For decades, scientists have operated under the assumption that this structure has a map-like organization, where specific fibers connect corresponding regions in each hemisphere to perform specialized tasks. Based on this model, damage to a part of the corpus callosum should result in specific, predictable communication breakdowns between the brain halves.

To test this idea, researchers turned to a unique group of individuals known as split-brain patients. These patients have undergone a rare surgical procedure called a callosotomy, where the corpus callosum is intentionally cut to treat severe, otherwise untreatable epilepsy. This procedure provides a distinct opportunity to observe how the brain functions when its main inter-hemispheric pathway is disrupted. Because the surgery is no longer common, data from adult patients using modern neuroimaging techniques has been scarce, leaving a gap in understanding how this profound structural change affects the brain’s functional networks.

The international research team studied six adult patients who had undergone the callosotomy procedure. Four of the patients had a complete transection, meaning the entire corpus callosum was severed. Two other patients had partial transections. One had about 62 percent of the structure intact, while another, patient BT, had approximately 90 percent of his corpus callosum removed, leaving only a small segment of fibers, about one centimeter wide, at the very back of the structure.

I wonder if this explains the French bureaucrat that years ago they discovered had a hydrocele occupying about 80% of his brain. They did determine, as I recall, that he had a diminished IQ (about 78, I think) but that he had enough basic function to do his job for years.

As I recall the hydrocele was centralized, so the exterior few centimetres of the lobes weren’t affected, so perhaps the hemispheres were still connected as a result.