ADDS A NEW DIMENSION
This fall, 2004, surgeons implanted 100 electrodes into the brain of a 25-year-old quadriplegic man and connected them to a computer that enables him to check his e-mail and choose a television channel with his thoughts alone.
And monkeys with similarly implanted electrodes have used brain signals to move cursors or robotic arms in two dimensions (Science, 24 January 2003, p. 496). Now, in a ground breaking development, two neuro-scientists from the Wadsworth Center, part of the New York State Department of Health in Albany, N.Y. have shown that similar feats may be possible without the dangers of inserting electrodes into the brain. This week, in the online Proceedings at the National Academy of Sciences, Wadsworth’s Jonathan Wolpaw and Dennis McFarland demonstrate a brain-computer interface (BCI) that can translate externally detected brain signals into both horizontal and vertical movement of a computer cursor.
“It’s earthshattering that we may be able to reconnect the brain to a paralyzed limb or a robotic arm without surgery’ says computer scientist Melody Moore, who directs the Brain Lab at Georgia State University in Atlanta. ~This disproves something people have been saying for a long time.” Two-dimensional cursor control, Moore says, could be used to operate a wheelchair, a chess-playing robot, or a computer mouse, for example. Once you have the second dimension, she notes, “the third dimension is within reach.” And that could enable full movement of a limb. Such a possibility seemed remote when Wolpaw, McFarland, and their colleagues described their first BCT in a journal in 1991. That system enabled a person to move a cursor on a screen up or down some indeterminate amount by raising or lowering the amplitude of electrical brain currents called mu or beta rhythms. By imagining actions such as running, floating, or moving one arm or the other, the subjects could influence these currents, which are generated by a brain area involved in sensation and movement. The researchers recorded the brain-wave changes using a detector called an electroencephalogram (EEG). It was a crude yes-no device, and skeptics doubted that this sort of BCI. which sums input from millions of neurons, would get much further.
In the following years, the Wadsworth group improved this one-dimensional BCI, enabling subjects to nudge a cursor a precise distance to land on one of four icons. Then, early last year, they translated that progress into two dimensions. One critical advance was a learning algorithm: The software program translating brain signals into cursor movement optimizes a user’s performance by adjusting its parameters based on the trials a user has completed so far.
Putting the BCI to the test, Wolpaw and McFarland asked four volunteers—two of them with spinal cord injuries to don caps speckled with 64 recording electrodes and to use whatever kind of imagery they could to push a cursor from the center of a computer screen to a target in any of eight possible locations on the periphery. As the volunteers did the task, a computer translated their brain’s mu and beta rhythms into horizontal and vertical cursor movements. After dozens of short practice sessions spread out over weeks, the two volunteers with spinal cord injuries could hit the targets routinely.-
10 December 2004, (pg.1878)
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