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Brain chip enables injured rats to control movements

Prosthesis bypasses damaged area to connect distant neurons

BRIDGE THE GAP   Injured rats can grab food normally when a newly created device, implanted in the brain, bypasses the damaged motor cortex to send messages to other parts of the brain.

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With a futuristic brain patch, brain-injured rats regained the ability to reach out and grab a bit of food. The results, in which a newly created electrical device bypasses a damaged brain area, may ultimately lead to ways to repair damage from stroke, blast injuries and diseases such as Parkinson’s.

The findings, published December 9 in the Proceedings of the National Academy of Sciences, “open the door for new experiments and new ways of approaching brain repair after injury,” says S. Thomas Carmichael of UCLA.

Scientists have made strides in brain-machine interface technology (SN: 11/16/13, p. 22), which routes brain signals to external machines such as prosthetic limbs or computer cursors. In contrast, the newly designed neural patch does all of its work inside the skull, routing signals from one part of the brain to another.

Scientists led by Randolph Nudo of the University of Kansas Medical Center in Kansas City tested their device on rats that had injuries in the motor cortex, a brain region that helps control movement. Before their injuries, rats could easily thread their paws through a slot to grab a morsel of food. Postinjury, the task became much more difficult.

But after eight days with the neural prosthesis, injured rats showed signs of improvement. After two weeks, the animals’ performance was as good as it had been before the brain injury, the team found.

With electrodes, the neural patch collects messages from neurons in the rats’ premotor cortex, a brain region involved in initiating movements. The device then converts these neural signals to small artificial electrical currents that ping neurons in another part of the brain, the somatosensory cortex. Usually the motor cortex acts as a middleman between these two areas, which work together to control movement. But when the motor cortex is injured, the neural patch bridges the damage and links activity in the premotor cortex to the somatosensory cortex.

Nudo and colleagues don’t yet know exactly how the device affects the brain. One possibility is that the prosthesis would be required permanently. Another is that the brain patch would be needed only temporarily if it stimulates the growth of new, long-lasting physical connections between neurons in the far-flung brain regions.

The rats’ brain damage approximates a human’s after a traumatic brain injury. People who have trouble moving after a stroke might also benefit from a similar neural patch. Although the results are intriguing, much more work will be needed to advance the technology and to understand how it would work in the human brain, says Eberhard Fetz of the University of Washington in Seattle. 

BRAIN PATCH  When a neural prosthesis is on and communicating between two distant brain regions, a rat regains the ability to reach a food pellet.

Credit: D.J. Guggenmos ET AL/PNAS 2013; adapted by Ashley Yeager

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