In a suburban Melbourne industrial estate, hidden in a clutter of brutalist buildings and parked trucks, tomorrow’s world is taking shape. Here, an Australian tech start-up called Cortical Labs has caused an internet sensation. More than 40 million people have watched a clip of disembodied human brain cells playing the 1990s video game Doom. These cells are kept in petri dishes, wired up to computers and trained to do whatever the researchers want.

“Right now, the cells play a lot like a beginner who’s never seen a computer,” says neuroscientist and Cortical Labs’s chief scientific officer, Brett Kagan. “But they can shoot, they can spin, they can seek out enemies and, while they die a lot, they are learning.” Doom is not only violent, it’s multidimensional, chaotic and unpredictable. Human players make decisions and act in split seconds. In the video the company posted on X, you can see the cell-controlled player moving through Doom’s tunnels and passageways, firing shots at enemies. The brain cells are behaving as though they, too, are deciding and acting.

Cortical Labs’s staff are mostly young and all are evangelistic about what they’re doing. The office attached to the lab could be any communal workspace in Silicon Valley. It’s opposite a yoga studio and a kitchen tiling company. But inside, it’s all very serious. I was shown a powerful microscope through which I could see the ghostly tangle of neurons. Their ganglia strings transmit and receive tiny electrical impulses, all superimposed over the neat grid on a microchip.

When the cells succeed in a game, a predictable signal is sent: 75 millivolts at 100 hertz for a tenth of a second, delivered across all eight stimulation electrodes at once. When the cells miss a shot in the game, it triggers something quite different: four seconds of disruptive electrical stimulation at 150 millivolts and 5 hertz, delivered at random through the eight electrodes. The idea is that the cells will want predictability rather than random disruption. It’s very Pavlovian, zapping brain cells to achieve desired outcomes. But the Cortical Labs team was keen to tell me that these cell clusters are not developed human brains.........

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