How can people function normally with only a fraction of a normal brain?
The comfortable certainty of having at least half a brain is unshakable. It is so beyond dispute that the philosopher Ludwig Wittgenstein used it as an example of knowledge that is certain even though we have no sensory experience to confirm it. However, biologist Donald R. Forsdyke, of Queen’s University, in Canada, points out in the journal Biological Theory that we need to account for cases of people who have led normal lives without a brain. Or, to be more precise, about 5% of a normal brain.
Brain scans of some recovered hydrocephalics show a vast area filled with fluid where other people had brain tissue. Their brain, what is left of it, has been compressed around the skull. Yet one of them went on to get a first class honours degree in mathematics. Clearly information-related content does not scale with brain size.
The conventional explanation for this is that brains have enormous redundancy and plasticity. But Forsdyke is sceptical: “The drastic reduction in brain mass in the hydrocephalic cases seems to demand unimaginable levels of redundancy and/or plasticity—superplasticity. How much brain must be absent before we abandon these explanations and admit that the standard model, however incarnated, will not work?”
So what other explanations could there be?
Forsdyke lists three. First, “Information relating to long-term memory is held within the brain in some chemical or physical form consistent with current knowledge of brain chemistry and physiology”. Second, “Information relating to long-term memory is held within the brain in some extremely minute, subatomic, form, as yet unknown to biochemists and physiologists.” And even more controversially, “Information relating to long-term memory is held outside the brain.”
The last of these, extracorporeal information storage, appeals to Forsdyke. Invoking Sherlock Holmes, he says, “How often have I said to you that when you have eliminated the impossible, whatever remains, however improbable, must be the truth?”
At the Neuroskeptic blog, however, it is argued that there is still no need to discard medical textbooks. The author says that the brain’s grey matter seems to be intact. The missing white matter, which normally provides connectivity, may be present but greatly compressed. More investigation is needed.
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