Last August, Casey Harrell spoke the first clear words his five-year-old daughter could remember hearing him say, a repeat of his wedding vows to her mother, Levana Saxon. The adults in the room cried.

The moment was possible thanks to a wave of innovation in one of the most challenging areas of medicine: reconnecting the brain to the body once something — an accident or an illness — has severed the ties. While Elon Musk’s Neuralink Corp. gets most of the attention and investor money in the space, academic labs and rival startups are notching significant advances in repairing that broken bond.

"I am using this in a very practical way, right now,” said Harrell, 46, who was diagnosed with amyotrophic lateral sclerosis (ALS) in 2019 and lost his ability to speak clearly a few years later.