When is a wristband enough, and when is a brain implant needed? · Grey Matter

A wristband reads motor commands where they arrive in the forearm muscles, so it works whenever the path from the motor cortex through the spinal cord and the nerves to the muscles still carries them.

When is a wristband enough, and when is a brain implant needed?

A wristband reads motor commands where they arrive in the forearm muscles, so it works whenever the path from the motor cortex through the spinal cord and the nerves to the muscles still carries them. For those users it needs no surgery and already handles cursor control, gestures and handwriting at about 21 words per minute. When that path is cut, as in a high spinal cord injury or advanced motor neuron disease, the commands never reach the skin, and the only place left to read them is the brain itself. That is why implanted interfaces are tested first in people with paralysis, where they also reach higher rates, such as speech decoded at 62 words per minute in 2023.