US researchers have developed a new mind-controlled device that reads brain signals, converts them into motion and thus helps stroke patients to retrain their brains to move their paralysed hands.

Stroke is the second leading cause of disability, after dementia, globally. Nearly six million die and another five million are left permanently disabled.The study showed that stroke patients who learned to use their minds to open and close the device fitted over their paralysed hands gained some control over their hands.By mentally controlling the device with the help of a brain-computer interface, participants trained the uninjured parts of their brains to take over functions previously performed by injured areas of the brain, the researchers said.

"We have shown that a brain-computer interface using the uninjured hemisphere can achieve meaningful recovery in chronic stroke patients," said Eric Leuthardt, Professor at Washington University in St. Louis.The device -- Ipsihand -- comprises a cap that contains electrodes to detect electrical signals in the brain, a computer that amplifies the signals, and a movable brace that fits over the paralysed hand.The device detects the wearer's intention to open or close the paralysed hand, and moves the hand in a pincer-like grip, with the second and third fingers bending to meet the thumb.

For the study, published in the journal Stroke, the team recruited 10 moderately to severely impaired stroke patients and trained them to use the device at home.Participants underwent a standard motor skills evaluation that measured their ability to grasp, grip and pinch with their hands, and to make large motions with their arms.After 12 weeks of using the device, the patients' scores increased an average of 6.2 points on a 57-point scale, the researchers said.