I am an explorer, but unlike my predecessors who used compasses and canoes to discover unknown lands, I used a scalpel and a small electrode to explore and map the human brain. Throughout my career, I was driven by the central question that has obsessed both scientists and philosophers for hundreds of years. Are mind and body one? Can the mind – thinking, reasoning, imagination — be explained by the functions of the brain? As a doctor, my first concern was always for my patients — to relieve the terrible suffering caused by diseases such as epilepsy. I found that by stimulating the exposed brain of a conscious patient with a small electrical current, the patient could tell me what they were feeling or seeing, and through this we could isolate the damaged part of the brain. I developed treatments for epilepsy based on this knowledge. But the procedure also opened a window to the mind, giving us for the first time a glimpse of how dreaming occurs, how memory works, and where speech and speech comprehension reside.”

While he was developing a surgical approach to the treatment of epilepsy, the neurosurgeon Wilder Penfield developed a new approach that became known as the “Montreal Procedure”.  He developed his method while his patients were awake and able to interact with him. Using local anesthetics, he removed the skull cap to expose the brain tissue of the conscious patient. When he probed certain areas of the brain, the patients would be able to provide him feedback on what they were experiencing at that very moment. Then, he was able to map the functions of tissues in different parts of the brain — a dream already made, but in vain, by Gall and Spurzheim in their treatise on the Anatomy and Physiology of the Nervous System. In most cases, he identified the precise location of the source of the seizure activity. He could then remove or destroy that bit of tissue to end the patient’s seizures. As he carefully probed the brain, he found that administration of a mild electric shock to one of the temporal lobes could cause the patient to recall precise personal experiences that had long been forgotten. He also discovered that stimulating parts of the cortex could evoke vivid and specific memories including sounds and smells. Epilepsy arising in the temporal lobe of the brain assumed special importance because of the re-excitation of past experiences that occurred when the cortex was stimulated during surgery.
It was an area that Penfield was passionate about, discovering and unlocking the hidden treasures in the human mind. Furthermore, Penfield completed his mapping of the brain.

It is a perfect summer day in a meadow of tall grass. J.V. is following her brother, lagging lazily behind. A show falls on the ground; something rustles the grass. J.V. turns and sees a strange man. He has no face, like a minor character in a dream. The man holds something writhing and indistinct. He asks “How would you like to get into this bag with snakes?”J.V.’ encounter is un unlikely milestone of twentieth-century thought. J.V.’s, was not in summer field but on an operating table in Montreal Neurological Institute. Her physician, Wilder Penfield, was attempting an experimental operation to relieve her violent epileptic seizures. The operating team had removed the side of J.V.’s skull to expose the temporal lobe of the brain. In order to locate the site of the attacks, Penfied probed the brain with an electrode to an EEG machine. The surgery was a collaboration between a physician and patient. J.V. had to remain conscious throughout and help locate the site seizures. When Penfield touched the probe to a certain spot on J.V.’s temporal lobe, she again found herself in the field of grass.  J.V.’s experience with the strange man had occurred seven years earlier, in Canada, in what we call the real world. She reported seeing herself as she was then, a seven-year old girl. J.V. had been frightened but not physically harmed, and ran crying home to her mother. These few moments of terror were to haunt her over and over. The man with the bag of snakes entered her dreams, made them nightmares. The trauma became interwoven with her epileptic seizures.  Under the EEG probe, J.V. not merely recalled but relived the encounter. All the richness of detail, all the lucid horror of the original experience, come back.

Penfield’s classic experiments of the 1930s inspired the famous “paradox brain-in-vats” by philosophy students. It goes like this: You think you are sitting there reading this book. Actually you could be a disembodied brain in a laboratory somewhere, soaking in a vat of nutrients.The nerve endings have been connected to a super-scientific computer which causes the person whose brain it is to have the illusion that everything is perfectly normal. There seem to be people, objects, the sky, etc; but really all the person (you) is experiencing is the result of electronic impulses traveling from the computer to the nerve endings. The computer is so clever that if the person tries to raise his hand, the feedback from the computer will cause him to ‘see’ and ‘feel’ the hand being raised. Moreover, by varying the program, the evil scientist can cause the victim to ‘experience’ (or hallucinate) any situation or environment the evil scientist wishes.


Doubts about the reality of the world are old. the Brain-in-vat is simply a stronger version of older paradoxes asking “How do you know this isn’t all a dream?”.

Best known of these is the Chinese tale of Chuang-tzu, dating from the fourth century B.C.. Chuang-tzu was the man who dreamt he was a butterfly, then awoke to wonder if he was a butterfly dreaming he was a man.
The most famous discussion along these lines is in Descartes’s Meditations. Descartes wonders if the external world, including his body, is an illusion created by an “evil genius” bent on deceiving him. “I will suppose that….some malicious demon of the utmost power and cunning has employed all his energies in order to deceive me. I shall think that the sky, the air, the earth, colours, shapes, sounds and all external things are merely the delusions of dreams which he devised to ensnare my judgement. I shall consider myself as not having hands or eyes, or flesh, or blood or senses, but as falsely believing that I have all these things”.

The Penfield experiments merely showed how Descartes’s metaphysical fantasy might be physically conceivable.
The eyes do not send the brain pictures, nor the ears sound. These senses communicate with the brain via electro-chemical impulses in the nerve cells. Each sell in the nervous system “sees” only the impulses of neighboring cells, not the external stimulus that caused them. The whole of our experience is a stream of nerve impulses. We have all “imagined” a world that might account for the unique set of nerve impulses we have received since (and several months before) birth.

In 1938 Albert Einstein and Leopold Infield proposed the following analogy
in our endeavor to understand reality we are somewhat like a man trying to understand the mechanism of a closed watch. He sees the face and the moving hands, even hear its ticking, but he has no way of opening the case. If he is ingenious he may form some picture of a mechanism which could be responsible for all he things he observes, but he may never be quite sure his picture is the only one which could explain his observations. He will never be able to compare his picture with the real mechanism and he cannot even imagine the possibility of the meaning of such comparison



Kumar R, Yeragani VK. Penfield – A great explorer of psyche-soma-neuroscience. Indian Journal of Psychiatry. 2011;53(3):276-278. doi:10.4103/0019-5545.86826.7.

Penfield W. The mystery of the mind: A critical study of consciousness and the human brain. Princeton University Press; 1975.

Penfield’s autobiography. Little, Brown and Co; 1977. No Man Alone: A Surgeon’s Life.

Labyrinths of Reason: Paradox, Puzzles, and the Frailty of Knowledge. William Poundstone. Penguin Books Ltd. 1991

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