It used to be thought that neural stem cells--which divide to produce nerve cells in an embryonic brain--shut down in adulthood.

ECONOMIST: Something new in mind

Neural stem cells are, unsurprisingly, rather tricky to harvest from living patients.

ECONOMIST: Stem cells

Surprisingly, the neural stem cells made their way far and wide in the developing embryos, from the nervous system to the liver, lung and intestine.

ECONOMIST: Stem cells

The point of the exercise, though, was to see whether neural stem cells could be obtained reliably, with a view to using them as a treatment.

ECONOMIST: Stem cells

To his delight, the extracted tissue thrived and grew, and many of the cells in the resulting culture did indeed contain proteins known to be characteristic of neural stem cells.

ECONOMIST: Stem cells

He has managed to derive neural stem cells from 16 of these patients, out of a total of 22, and believes that success depends on which region of the brain is affected.

ECONOMIST: Stem cells

Dr Frisen's team, together with NeuroNova, a Swedish biotech firm, is busy trying to identify some of these chemicals, and working out the genes and molecular pathways that are turned on in responsive neural stem cells.

ECONOMIST: Stem cells