Say the researchers:

Until now, brain-computer interfaces were designed to decode the activity of neurons known to be associated with movement of specific body parts. Here, the researchers discovered that any motor cortex cell, regardless of whether it had been previously associated with wrist movement, was capable of stimulating muscle activity. This finding greatly expands the potential number of neurons that could control signals for brain-computer interfaces and also illustrates the flexibility of the motor cortex.

Human implementations for the technology are at least a decade away, but this discovery could be a game-changer for dealing with paralysis. One possibility would be to connect the motor cortex with an area of the spine below an injury. Signals would be re-routed around the damaged spinal cord, and could allow the brain to regain control of the paralyzed body parts affected by the injury.