Johnson isn't alone in believing that "neurotechnology" could be the next big thing. To many in Silicon Valley, the brain looks like an unconquered frontier whose importance dwarfs any achievement made in computing or the Web.

According to neuroscientists, several figures from the tech sector are currently scouring labs across the U.S. for technology that might fuse human and artificial intelligence. In addition to Johnson, Elon Musk has been teasing a project called "neural lace," which he said at a 2016 conference will lead to "symbiosis with machines." And Mark Zuckerberg declared in 2015 that people will one day be able to share "full sensory and emotional experiences," not just photos. Facebook has been hiring neuroscientists for an undisclosed project at Building 8, its secretive hardware division.

Even when speaking to a computer program like Alexa or Siri, you can convey at most about 40 bits per second of information and only for short bursts. Compare that to data transfer records of a trillion bits per second along a fiber-optic cable.