TWO ARMS GOOD, THREE ARMS BET­TER

Focus-Science and Technology - - INNOVATIONS -

Be­cause two arms just aren’t enough, re­searchers from the Hiroshi Ishig­uro Lab­o­ra­tory in Ky­oto, Ja­pan, have taught vol­un­teers to con­trol a ro­botic third arm through a brain-ma­chine in­ter­face.

Par­tic­i­pants in the experiment were chal­lenged to balance a ball on a board us­ing their hands, and pick up a bot­tle us­ing a ro­botic third arm. Fif­teen sub­jects took part, and eight of them man­aged the task suc­cess­fully.

For now, the robot arm is quite ba­sic: it can only open and close its hand. The brain-ma­chine in­ter­face is sim­i­larly rudi­men­tary: it’s a cap fit­ted with elec­trodes that mea­sures the brain’s elec­tri­cal sig­nals. Be­fore the test, par­tic­i­pants imag­ined open­ing and clos­ing the ro­botic hand, and those brain sig­nals were recorded and turned into an in­struc­tion for the ro­botic arm.

Uses for ex­tra limbs have al­ready es­tab­lished. An MIT con­cept de­vice de­vel­oped in 2012 saw users wear ex­tra limbs like a back­pack. They were used to hold tools and parts in man­u­fac­tur­ing, and to sup­port the user in sit­ting po­si­tions. But while it’s a long way off be­ing prac­ti­cal, this is the first time that an ex­tra limb has been con­trolled straight from the brain. In the past, ro­botic pros­thet­ics have been con­trolled us­ing sig­nals from mus­cles or ex­ter­nal joy­sticks, and they’ve usu­ally been in­tended as re­place­ment limbs, not sup­ple­men­tary ones.

The re­searchers also noted that suc­cess in the task de­pended heav­ily on the par­tic­i­pants’ abil­ity to mul­ti­task. They sug­gested that op­er­at­ing the ex­tra limb through the brain-ma­chine in­ter­face might help users im­prove their mul­ti­task­ing abil­i­ties.

The par­tic­i­pants had to move a ball be­tween coloured shapes on a board, while grab­bing a bot­tle with a robot hand

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