Even A Very Weak Signal From The Brain Might Help Paraplegics

A report that four young men who are paralyzed below the waist were able to move toes, ankles or knees when their lower spine was electrically stimulated was hailed as a breakthrough.

But it's hard not to be skeptical about anything labeled a medical breakthrough these days, and that's especially true when it comes to spinal cord regeneration, which has seen more than its share of hype. For the quarter of a million people with spinal cord injuries, dashed hopes can be devastating.

A treatment or cure for spinal cord injury remains elusive, but the study by researchers at the University of Louisville appears to add important information: Even a very weak signal from the brain can trigger movement.

To figure out what this means, we talked it over with John Donoghue, director of the Brown Institute for Brain Science and leader of the BrainGate II project, which in 2012 made it possible for two people immobilized by strokes to control a robotic arm with their thoughts. He wasn't involved in the Louisville research. The conversation has been edited for length and clarity.

When a spinal cord is severed, that causes paralysis. There have been decades of efforts to bridge that gap. Some reports say that's what's happened here, but others say no. What did happen?

It isn't like there was no connection there, it literally got severed, and then you got something. There has to be a connection to the brain.

The important thing, I think, is that it's not magic. It's sort of a hidden or masked connection. This suggests that when they put in the electrical stimulation, they revealed that there's a hidden connection that's hard to detect. And if it's there, it's really, really weak. You're doing something that reveals that the pathway is there.

In the past you and other researchers have been skeptical that having a few remaining neurons bridging that gap, or restoring a few, would be enough to restore function. Does this change your thinking?

This is wonderful news, I think. But these people are not playing basketball or anything. Is this functional movement? Well, in a sense, but to me, it's pushing us in a direction to say that for people with damaged spinal cords there's a way to get a small input to have a meaningful effect.

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Even A Very Weak Signal From The Brain Might Help Paraplegics