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Real human half brain anatomy isolated on black background
Real human half brain anatomy isolated on black background

A Neurosurgeon on Why Some People Function With Only Half a Brain

The study results are reassuring and they point to two larger truths

Yesterday, we ran a story about a recent study in which 40 people who had half of their brains removed (hemispherectomy) as children — due to intractable epilepsy — did unexpectedly well on psychological tests. Some say that it’s easy to explain because the brain has so many redundant elements. But is that all we need to know? We asked pediatric neurosurgeon Michael Egnor for some thoughts on that approach and he replied:

The means by which people with major parts of their brains removed maintain function are not understood. It’s nonsense to say, as some do, that “The brain is massively parallel and recursive and functions under network rules and laws.” That’s typical neuroscience gibberish. The fact is that neuroscientists study the brain using network theory, and… surprise!… the brain seems to be a network.

Michael Egnor

The ancient Greeks studied the brain according to caloric theory, and… surprise!… the brain seemed to be a heat generator.

The 19th century physiologists studied the brain using mechanical concepts and… surprise!… the brain seemed like a machine.

Quantum physicists (e.g. Roger Penrose) study the brain as a quantum system and… surprise!… it looks like a quantum system!

Werner Heisenberg was that rare scientist who was a capable philosopher, and he understood this silliness very well. He said (one of my favorite quotes in science):

“What we observe is not nature itself but nature exposed to our method of questioning.” – Werner Heisenberg, Physics and Philosophy: The Revolution in Modern Science (1958)

The most important thing in science is not the answer you get but the question you ask.

If you study the brain using computational models, it will look like a computer. If you study the brain using models of biochemistry, it will look like a chemistry set. If you study the brain using electrical circuit models, it will look like an electrical circuit. We only see nature when it is exposed to our method of questioning.

We don’t know the right questions to ask about the brain. How can we possibly get the right answers?

That’s why I like ancient philosopher Aristotle‘s theory of the mind. It is a logically coherent model, and experiments can be interpreted in light of it. Remarkably, the mind behaves in many ways just like Aristotle thought it would. And Aristotle knew nothing of networks, parallel processing, or computers.

Regarding the claim that “the redundancy and network structure of the brain” account for preserved function, it’s just hand-waving. No one knows how the mind relates to the brain to begin with, so how could we know that redundancy and network structure are responsible for preservation of function?

My computer is a network and has redundancy. But if I cut it in half with a chainsaw it sure as hell won’t work. Neuroscientists are just making stuff up. It’s confabulation, not science.

On the specific issue of preserved function after hemispherectomy, he writes,

Neurological function is generally preserved, probably due to better seizure control and less need for sedating, anti-convulsant drugs. The diseased hemisphere was never particularly functional anyway, and brain function in the healthy hemisphere was probably adequate for many years prior to the surgery.

My problem with the “redundancy” argument is that it assumes that the brain generates the mind via its “parallel recursive” nature or whatever, which is not only a leap beyond what is really known in the science, but is metaphysical gibberish. There is no metaphysical understanding of matter in the materialist framework that can even begin to explain mind function in terms of brain function. So it is hopeless to attempt to explain mind preservation as “parallel recursive” circuits or whatever. It’s just invoking magic.

We don’t know (from a materialist perspective) how it is even possible for the brain to relate to the mind, so how could we possibly know how mind is preserved after brain surgery? It’s just confabulation dressed up to look like science.


You may also wish to read: People with half their brains removed do well on psych tests. In a recent study, adults who had had hemispherectomies as children — to combat severe epilepsy — performed within 10% of other study subjects on face and word recognition. Findings like this are a challenge to those who insist that the mind is simply what the brain does. The mind may not be split or removed when the brain is.


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A Neurosurgeon on Why Some People Function With Only Half a Brain