Oxford researchers discover how the brain adapts to congenital one-handedness or the loss of a hand.

How the brain lends a handA new study by Oxford University scientists offers fresh insight into how the brain adjusts to the loss of a hand, with the prospect of improved treatments for amputees.

Researchers found that people with a missing hand who can do two-handed tasks nearly as well as able-bodied people — such as putting on socks or using a knife and fork — have brains that are almost indistinguishable from those of able-bodied people.

‘The brain doesn’t care if you are born with only one hand. The brain is not fussy about whether there is a hand at the end of the arm, a prosthetic or a “stump” — so long as it is used in a similar way,’ said lead author Dr Tamar Makin, from Oxford’s Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB).

Thirty-eight participants — 14 with one arm, 24 with two — were asked to rest inactively in an MRI scanner while researchers tracked their brain activity. A symmetrical pattern was found in those with two hands. Those with a missing hand, as a group, were more likely to have an asymmetrical pattern, due to differences in brain areas linked to the missing hand versus the intact hand.

However, the more people used the stump in everyday life, the more symmetrical the pattern of their brain activation. The few people with a missing hand who functioned nearly as well as two-handed people showed brain activity that was almost indistinguishable from those with two hands.

Study co-author Dr David Henderson Slater, Consultant at the Nuffield Orthopaedic Centre in Oxford, said: ‘We have always known that some people adapt to the loss of a limb very soon, and start to make changes in the way they use other parts of their body to compensate for not having a hand.  It is encouraging to see that there is hope for improvement even after devastating injuries, and to understand better what is going on inside the brain to make these behavioural adaptations. We may be able to incorporate this knowledge into the therapy we offer to new amputees.’

The new study is published in the journal eLife.

It follows an earlier study involving Dr Makin’s team which compared arm and brain activity in two contrasting groups of one-handed people — those born with only one hand and those born with both. It found that people born with one hand tend to use the remaining part of the arm in daily life, whereas those who have lost a hand use their opposite and intact arm much more extensively. For each group, however, the same brain area is activated — the area corresponding to the missing hand. The implication is that the limb which is utilised to compensate — whether it is the impaired arm or the intact one — takes over the brain area which would otherwise have been used by the absent hand.

This article is based on an item first published on the Oxford University News and Events page. Image © bikeriderlondon via Shutterstock.