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IN THE 2nd century AD, Galen of Pergamon, a philosopher and surgeon in the Roman Empire, held a public demonstration in which he got a volunteer to press on the exposed brain of a live, conscious pig. The animal passed out, but the heart kept beating. After the volunteer stopped, the pig regained consciousness.

Fast forward to 1860, when a Parisian man tried to blow his brains out with a pistol. Instead, he shot away his frontal bone, leaving the anterior lobes of his brain bare but undamaged. He was rushed to the H么pital St Louis, where a doctor, Ernest Aubertin, spent hours trying to save his life.

In the process, Aubertin discovered that if he gently pressed a spatula on the patient鈥檚 brain while he was speaking, speech was suddenly suspended. Aubertin reported that 鈥渁 word begun was cut in two鈥�. 鈥淪peech returned as soon as pressure was removed,鈥� he said.

Eighty years later, Wilder Penfield, a neurosurgeon in Canada, was carrying out brain operations to relieve chronic temporal-lobe epilepsy. Using delicate electrodes, he mapped the least damaging cuts possible.

For patients, stimulating these regions produced the strangest experiences. A piano being played. A telephone conversation. The sight of a man and a dog walking along a road. These didn鈥檛 feel like memories so much as glimpses of another world.

All these fascinating stories are told in a new book, The Idea of the Brain by Matthew Cobb, a zoologist at the University of Manchester, UK. Here, he argues that the analogies and metaphors we use to describe the brain both enrich our understanding of that mysterious organ 鈥� and hamstring further progress.

Study the brain as though it were a machine and in the end (and after much good work) you will run into three kinds of trouble, he says.

鈥淪tudy the brain as if it were a machine and in the end you will run into three kinds of trouble鈥�

First, you will find that you cannot reverse-engineer complex systems. Take what happened to two neuroscientists, Eric Jonas at the University of California, Berkeley, and Konrad Paul Kording at Northwestern University, Chicago. In 2017, they borrowed techniques normally used for studying the brain to take apart the computer chip that enabled 1980s computers to run games such as Donkey Kong, Pitfall! and Space Invaders.

They failed to achieve a meaningful forensic understanding of the chip, even though its makers had a clear explanation for how it worked.

A second problem, says Cobb, is the way technical terms lose their specific meanings. According to Cobb, neuroscientist Romain Brette at the Institute of Vision, Paris, has a particular hatred for that staple of neuroscience, the idea of 鈥渃oding鈥�, first invoked by physiologist Edgar Adrian in the 1920s.

Technically, in neuroscience a code is the hypothetical link between a stimulus and the activity of a neuron. Today, many researchers think of neural codes as representations of that stimulus, which is a real problem, because it implies that there must be an ideal observer within the brain, watching and interpreting these representations. It may be better, says Brette, to think of the brain as constructing information, rather than simply representing it 鈥� but we have no idea, yet, how such an organ would function. It wouldn鈥檛 be a computer as we know it.

Finally, we take too much comfort and encouragement from our own metaphors. Do advances in artificial intelligence really bring us closer to understanding how our brains work?

Cobb鈥檚 hollow laughter is all but audible. 鈥淢y view is that it will probably take fifty years before we understand the maggot brain,鈥� he writes.

One last history lesson from The Idea of the Brain is instructive. In the 1970s, 20 years after Penfield鈥檚 electrostimulation studies, Michael Gazzaniga, a cognitive neuroscientist at the University of California, Santa Barbara, studied the experiences of people whose brains had been split in a desperate effort to control their epilepsy.

He discovered that each half of the brain was, on its own, sufficient to produce a mind, albeit with slightly different abilities and outlooks in each half. 鈥淔rom one mind, you had two,鈥� Cobb remarks. 鈥淭ry that with a computer.鈥�

Hearing the news brought psychologist William Estes to despair. 鈥淕reat,鈥� he snapped, 鈥渘ow we have two things we don鈥檛 understand.鈥�

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