The link to machines

• A headset worn on the scalp controls a device without surgery In wide use

  Electrodes pressed against the scalp pick up the faint electrical hum of the brain through the skull. The signal is coarse, but it is enough to pick a letter, steer a toy or tell when a person is calm, and it needs no surgeon. Headsets that do this have been sold to the public since 2007, as toys, meditation aids and gaming controllers, in the hundreds of thousands. It is the only link to a machine on this branch that is in wide use, and by far the weakest.

• A brain implant gives a person touch from a robotic hand First human

  Signals going the other way: pressure sensors on a robotic hand's fingers drive tiny currents into the part of the brain that feels the hand, and a paralysed man feels his own fingers being touched when the robot's are. Reported in 2016, it closed the loop between brain and machine for the first time in a person, and made the robotic arm he already controlled by thought much faster to use.

• A brain implant turns intended speech into text at conversational speed First human

  A person who can no longer speak tries to, and the implant reads the brain's instructions to the mouth and throat and turns them into words on a screen. In August 2023 two groups reported people with paralysis producing sixty to eighty words a minute this way, from large vocabularies, which is within sight of the hundred and fifty of ordinary conversation. It is the fastest a brain has yet talked to a machine, and the first point on this branch's bandwidth series.

• A fully implanted wireless brain chip lets a paralysed person control a computer First human

  A device under the skin and skull reads the brain's signals and sends them out by radio, with no wire through the skin: nothing to plug in, nothing to infect, usable at home. Wired implants have done this in laboratories since the 1990s. The first fully implanted wireless one was used at home by a woman with motor neurone disease in the Netherlands, reported in 2016, to select letters on a screen. The first high-channel version, with a thousand electrodes, went into a person in January 2024 and let him play chess and games by thought.

• A wired brain implant lets a paralysed person control a cursor First human

  The original brain-computer link: an electrode in the part of the brain that plans movement, a wire out through the skull to a computer, and a cursor that moves where the person means it to. The first paralysed person to do this was reported in 1998, with a single electrode; the hundred- electrode version that most later work builds on went into a man in 2004. Every speech, touch and robotic-arm result on this branch grew from it. It has never left the laboratory, because the wire does.

• A brain link carries more information per second than speech Idea only

  The number the merger argument rests on. Speech moves about forty bits of information a second, in every language measured; typing, less. A brain link that beat speech would be the first time a person had a faster way out of their own head than the mouth, and the stated goal of the best-funded implant companies. No link has come close: the fastest, the 2023 speech decoders, move the equivalent of speech at half speed with errors, and they do it by reading the instructions for speech itself. Whether the brain can originate more than it already says is the open question.

• An uploaded animal brain reproduces something it learned Idea only

  The long shot behind every story about uploading a mind: read a brain out completely, run the reading as a program, and get the same creature back. The honest test is small. Teach an animal something, map its brain, and see whether a simulation built from the map does what the animal learned, without being taught again. The complete wiring diagram of a fruit fly's brain was published in 2024 and a simulation built from it produces some of the fly's reflexes, but no simulation has yet reproduced a memory that one particular animal formed. That is the gap.

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