When the ads for Mars vacations came on the TV, Doug Quaid couldn’t turn away. He thought about Mars at work, dreamed about it at night, badgered his wife about going there. She reminded him that they couldn’t afford it—and anyway, Saturn is much nicer. But he could not get Mars out of his head. So after work at the construction site, he went to visit Rekall, Incorporated. Salesman Bob McClane described their memory implant services:
Bob: When you go Rekall, you get nothing but first class memories. Private cabin on the shuttle, deluxe suite at the Hilton, plus all the major sites: Mount Pyramid, the Grand Canal, and of course, Venusville.
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| Excerpted from: Flicker, by Jeffrey M. Zacks Oxford University Press, 2014 Adapted from Chapter 10: “Virtual Futures” |
Doug: But how real does it seem?
Bob: As real as any memory in your head.
Doug: Come on, don’t bullshit me.
Bob: No, I’m telling you, Doug, your brain will not know the difference—and that’s guaranteed, or your money back.
Doug was sold. Within a few minutes, he was being sedated and slid into a large circular machine to have his artificial memories inserted directly into his brain. But something went wrong, and the next thing he knew he was on the run from a gang of men with big guns.
The film is Paul Verhoeven’s Total Recall, with Arnold Schwarzenegger as Douglas Quaid. The theme is one that has come up repeatedly in the movies of the last few decades: directly manipulating memory using hypothetical future neuroscience techniques. A few other examples: Eternal Sunshine of the Spotless Mind (2004), The Matrix (1999), Inception (2010), eXistenZ (1999).
In the future, will we be downloading experiences to entertain, to teach ourselves martial arts, cure our depression, or implement a business strategy? The technologies that these movies envision are pretty unrealistic. But let’s consider one more plot: Men and women in lab coats surround an operating table. Their faces are hidden by surgical masks and hats. The table is completely covered by sterile sheets, except for a rectangle, about 6 by 4 inches, through which pulsing brain tissue can be seen. One of the people in lab coats, a man, lifts a thin probe, leans in, and touches it to the exposed living brain. From beneath the sheet comes a voice: “I can see the most wonderful lights.” A little later, “Did you pour cold water on my hand?” Then, “I can smell burnt toast.”[i]
Another science fiction film? No, this is real. And it’s not even the latest thing—not by a long shot. I just described a brain surgery conducted by the Montreal neurosurgeon Wilder Penfield in 1934, to treat a patient with a severe seizure disorder. Penfield, building on studies in animals, used electrical stimulation to probe the function of brain areas before operating. These methods proved invaluable, and are now standard procedure in neurosurgery units around the world. Over decades, Penfield and his colleagues were able to establish that the evoked visual responses in primary sensory and motor areas, and in parts of the brain controlling speech, are predictable and replicable. Creating experience by directly stimulating the brain is by no means science fiction; it is an everyday part of medical practice.
But it has limits. The sensory and motor experiences that we can evoke by stimulation are crude at best—the feel of a touch on your arm or leg, or the visual impression of flashing lights. And of course, there is the obvious practical limitation: You have to have your skull cut open to try it out. I doubt anyone will be showing up for elective brain surgery as entertainment, but it turns out that there are new tools that enable neuroscientists to stimulate the brain in ways that are relatively safe, noninvasive, and with little lasting consequence. These methods may make it possible to take some of Penfield’s techniques out of the operating room.
Here is one option: The business end of the machine looks like an infinity symbol, a figure eight encased in white plastic. The device is called a transcranial magnetic stimulator, and it is one of the more dramatic tools in the neuroscientist’s toolkit. Transcranial magnetic stimulation (TMS) uses magnetic fields to stimulate small bits of brain—in healthy people, without any surgery, and, in most cases, with minimal aftereffects. The unique features of TMS are that it can alter the workings of a pretty small piece of brain, do so very quickly (in a few hundredths of a second), and just as quickly shut off the effect. However, compared to stimulating with a small electrode, TMS is a pretty blunt instrument. A TMS pulse affects a small patch of brain under the magnetic coil—but a small patch of brain is still millions of neurons. It cannot cause any particular neuron or group of neurons in that volume to fire. And the firing induced by the TMS pulse is quite different from normal neural activity. Neuroscientists often think of TMS as working like a quick instantaneous brain lesion that we can turn on and off.
Is this safe? Quite. Dosed out as one or a few pulses at a time, TMS has been shown to have virtually no long-term consequences for brain function. The main drawback is that, depending on where the targeted area is located, some current may be induced in the scalp as well as in the brain. You can’t feel current in the brain, but current in the scalp can cause muscles to twitch and can stimulate pain receptors in the skin, producing a pinching or pricking sensation.[ii] I find it to be no big deal, as do most people who try it.
The effects we can produce with TMS are similar to those that Penfield discovered with his electrodes applied directly to the brain. It will not create a detailed shape or a particular sound, but it could still do some things that might be pretty entertaining. Imagine you are watching a car chase. The Mustang’s brakes are out, and the car is headed for a cliff. As the car swerves, we zap the part of your brain
