Half a brain kept every major network

Researchers at Caltech scanned six high-functioning adults who had a hemisphere removed in childhood, to see how the networks that normally span both halves of the brain had organized in the one that remained.

The team recorded each person's brain activity at rest and compared it with healthy controls and a normative sample of 1,482 people. Within every familiar network, the single remaining hemisphere was as strongly connected as an intact brain, and connections between different networks were markedly stronger in almost all six.

The authors read that extra cross-talk between networks as one way a single hemisphere takes on the work of two. Six people is a small and unusual sample, and the scans show how the brain is wired at rest, not how well any particular skill works.

One hemisphere, every network in place.