Today, some people want their brain to end up in a jar by choice—not for the benefit of medical research, but because they figure they might need it again. Brain freezing is big business: Many hundreds of people have paid up to $200,000 or so for their bodies—or, for less than half that cost, just their heads—to be cryogenically preserved after death. The hope is that science will one day enable the brain to be revived and the person, in effect, to be brought back to life—and perhaps then to live forever. (You won’t necessarily want your original body, especially if you died from some fatal accident or illness.)
Currently there seems to be no actual prospect that a frozen brain could be revived. Experts point out that today’s cryogenic techniques inevitably cause damage to tissues, and that thawing would induce still more. But brain-freezing immortalists contend that the technology offers a glimmer of hope that death can one day be cheated. “If you can bridge the gap (it’s only a few decades), then you’ve got it made,” writes the computer scientist Ralph Merkle. “All you have to do is freeze your system state if a crash occurs and wait for the crash technology to be developed ... You can be suspended until you can be uploaded.”
A crash? Uploaded? You can see where this is going: The idea is that the brain is just a kind of computer, full of data that can be stored on a hard drive in a file labeled “You.”
As Merkle sees it, your brain is material, governed by the laws of physics; those laws can be simulated on a computer; therefore your brain can be, too. Although the network of neural connections in the brain is astronomically complex, we can put an upper limit on how many bits should be needed to encode it. Uploading the contents of a brain will need a computer memory of about 1018 bits, performing around 1016 logic operations a second, Merkle calculates. That’s perfectly imaginable with the current rate of technological advance.
According to this “transhumanist” vision, we will soon be able to live on inside computer hardware. The brain in a jar becomes the brain on a chip.
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Such heady visions of brain downloads ignore the fact that the brain is not the hardware of the person but an organ of the body. Several experts in both AI and cognitive science argue that embodiment is central to experience and brain function. At the immediate physiological level, the brain doesn’t just control the rest of the body, but engages in many-channeled discourse with its sensory experience, for example via hormones in the bloodstream.
And embodiment is central to thought itself, according to the AI guru Murray Shanahan, who acted as a consultant on Alex Garland’s 2014 AI movie Ex Machina. Shanahan, a professor of cognitive robotics at Imperial College London, writes that cognition is largely about imagining the consequences of physical actions we might make in the world—a process of “inner rehearsal” of future scenarios.