Software turns ‘mental handwriting’ into on-screen words, sentences

(Stanford Medicine News Center) - Call it mindwriting. The combination of mental effort and state-of-the-art technology have enabled a man in his 60s with immobilized limbs to communicate by text at speeds rivaling those achieved by his ablebodied peers texting on a smartphone.

In a study of the communication method, a brain-computer interface implanted in the man’s brain sent signals to a computer with software that quickly converted his thoughts about handwriting into text on a computer screen.

The man, who lost practically all movement below his neck because of a spinal-cord injury in 2007, produced text at a rate of about 18 words per minute. By comparison, able-bodied people of the same age can punch out about 23 words per minute on a smartphone.

For the study, Jaimie Henderson, MD, professor of neurosurgery, placed two brain-computer-interface chips, each the size of a baby aspirin, in the left side of the man’s brain.

The man then concentrated on writing individual letters of the alphabet on an imaginary legal pad with an imaginary pen. The chips picked up signals from neurons firing in the part of the motor cortex — a region of the brain’s outermost surface — that governs hand movement.

Those neural signals were sent via wires to a computer, where artificial-intelligence algorithms decoded the signals and surmised the man’s intended hand and finger motions.

The algorithms were designed in Stanford’s Neural Prosthetics Translational Lab, which Henderson co-directs with electrical engineering professor Krishna Shenoy, PhD.

Using this approach, the man was able to write more than twice as quickly as he could using a previous method developed by the Stanford researchers, who reported those findings in 2017 in the journal eLife.