Elon Musk is preparing for the most consequential launch of his career. But this one isn’t rocket science—it’s brain surgery. Musk’s company Neuralink Corp. is seeking a volunteer for its first clinical trial, meaning it’s looking for someone willing to have a chunk of their skull removed by a surgeon so a large robot can insert a series of electrodes and superthin wires into their brain. When the robot finishes, the missing piece of skull will have been replaced with a computer the size of a quarter that’s meant to stay there for years. Its job will be to read and analyze the person’s brain activity, then relay that information wirelessly to a nearby laptop or tablet.

For the purposes of the trial, an ideal candidate would be an adult under age 40 whose four limbs are paralyzed. Such a patient would likely have Neuralink’s implant inserted into what’s known as the hand knob area of their premotor cortex, which governs the hands, wrists and forearms. The goal is to show that the device can safely collect useful data from that part of the patient’s brain, a key step in Neuralink’s efforts to convert a person’s thoughts into a range of commands a computer can understand.