Short of minor lesions or infarcts, most high-functioning adults have an intact cerebral cortex. Yet, a surprising result published anecdotally in Science in 1980 caused a lot of scientists to take note of Dr. John Lorber's hydrocephalus patients in England.
Most famously, Lorber reported:
There's a young student at this university...who has an IQ of 126, has gained a first-class honors degree in mathematics, and is socially completely normal. And yet the boy has virtually no brain...instead of the normal 4.5 centimeter thickness of brain tissue between the ventricles and the cortical surface, there was just a thin layer of mantle measuring a millimeter or so.
Now, arguing that the subject had "virtually no brain" is perhaps a bit of hyperbole, but the fact remains, he had accomplished an academic feat which many "normal" humans have not. What's even more astonishing about this particular case is that this subject was purportedly not even aware of his condition until the initial brain scans were performed.
Aside from 1-2 other publications in peripheral journals around the same time period, I have never heard anything further about these patients that Dr. Lorber was following.
In the intervening 30+ years, have there been any follow-up scans/studies of these patients particularly those featuring the mathematics scholar mentioned above?
What mechanisms does the cortex use in these unusual circumstances to counter the effects of decreased cortical thickness? Are the cortical columns shorter, and in what sense does their connectivity compensate for lower neuron counts/lower cell densities?
Lewin, R. (1980). Is your brain really necessary? Science 210(4475):1232-1234.