Musk didn’t seem to think this was essential. “A lot of people think, ‘I couldn’t possibly work at Neuralink because I don’t know anything about how brains work,’” he said at last Friday’s demo. “Well, that’s OK. You can learn. But we need software engineering, we need mechanical engineering, electrical engineering … chip design, robotics, and all the things a company needs to work.”

At some point, someone is going to have to know something about how brains work. The Neuralink picks up electrical signals—the “spikes” or “action potentials” that run the length of neurons when they’re activated, and signal the squirting of neurotransmitter chemicals across synapses. But some of what the team said seemed to imply that given enough of those signals, they’d be able to interpolate actual thoughts or memories. Nobody’s really sure that’s true. In fact, it’s possible (though unlikely) that the electricity, the movement of charged ions into and out of neurons, is just an epiphenomenon—the exhaust that a brain coughs out while doing the work of creating and maintaining consciousness.

Even if it’s possible to correctly infer mental state from those electrical signals (and it probably is), they still just happen to be what people can measure. “There are things you can do with the neural signals. They’re the expression of things like memories. The retrieval of a memory will be instantiated, we think, in terms of a pattern of brain activity. That’s true,” Frank says. But that’s not how people store that memory for future retrieval, which doesn’t bode well for recording specific ones, saving them somewhere else, and replaying them. “The storage of the memory involves huge numbers of chemical reactions at synapses between brain cells,” Frank says. “Those things can be modified by brain activity, but they’re not the same as brain activity.”

In other words: The electrical activity of the brain happens while you are thinking or remembering, but it may not be what you are thinking or remembering. Just being able to sense and record that activity isn’t recording actual thought. It correlates, but may not cause.

Musk went even farther, though. “It’s read-write in every channel,” he said. He meant that each one of those 1,024 channels can both pick up signals from, and send them to, adjacent neurons. Now, Musk didn’t specify in what sense he meant that phrase. Neuroscientists talk about the capacity to “read out” signals from a brain, and the ability to “write in,” so send signals back. They can read out signals from motor neurons to control a robot arm, for example, or write in auditory information, sound, via a cochlear implant. They’re working on doing the same for sending images to the retina, or the visual cortex. Researchers can record what neurons are doing, and stimulate them so they activate.

Computer engineers, though, talk about reading and writing as getting digital information from a storage medium, or putting information in one.

Is Musk using the terminology interchangeably? Or does he think that the technology’s ability to do the primitive version will lead to the more sophisticated one? I don’t know.

But if it’s the latter, Neuralink might be headed for a metaphor-based failure. Neuroelectrical writing-in is very different from the digital version. “The techniques they have to write information in are primarily electrical stimulation, and that’s just awful,” Frank says. “Imagine when you wrote to a hard drive that you targeted a particular sector or byte, but what you hit was five other bytes first. That’s what happens with electrical stimulation to the brain.” Axons, the long projecting connections between neurons, have a lower activation threshold than the cells themselves. So sending a signal pulse down one of those Neuralink electrodes activates that mesh of connections, a whole lot of cells, before hitting a target neuron—and that’s assuming you know exactly which neuron to target.