A gene for Alzheimer's makes you smarter

Jerry Pournelle has posted some discussions on the notion of "overclocking the brain" – physiological changes that increase intelligence at the cost of a higher chance of dementia. Now, here's a piece from New Scientist showing that a gene that increases the chance of developing Alzheimer's makes its carriers smarter. A gene for Alzheimer's makes you smarter.

The "allele" in question is epsilon 4, a version of the apolipoprotein E gene (APOE). Having one copy increases the risk of developing Alzheimer's at least fourfold compared with people who have other forms of the gene. A person with two copies has up to 20 times the risk.
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Her team asked 20 to 35-year-olds to remember which pictures of animals or landscapes they had seen before, while having their brains scanned with functional MRI. It was an easy task and all performed equally well. But a brain region critical to memory lit up more strongly in epsilon 4 carriers than in the others, raising the intriguing possibility that carriers' brains get overworked in early life, only to be worn out by the time they hit old age. MacKay wouldn't go that far, but she says: "It's possible that your brain is having to work harder when it's younger and this may have consequences for later life."

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My candle burns at both ends;
It will not last the night;
But ah, my foes, and oh, my friends--
It gives a lovely light!

— Edna St. Vincent Millay