Several companies are testing brain implants—why is there so much attention swirling around Neuralink?

Putting a computer inside someone’s brain used to feel like the edge of science fiction. Today, it’s a reality. Academic and commercial groups are testing “brain-computer interface” devices to enable people with disabilities to function more independently. Yet Elon Musk’s company, Neuralink, has put this technology front and center in debates about safety, ethics, and neuroscience.