"The Forgetting" by David Shenk

"The Forgetting" spreads out all over the place, from the threat of a new epidemic, through the mechanics of human memory, to a glimpse at the world of high-end, high-stakes medical research. Shenk intersperses his commentary with first-person accounts of the loss of function. He listens in on a support group for Alzheimer's sufferers and looks back into literary history: Ralph Waldo Emerson and Jonathan Swift were probable Alzheimer's sufferers and wrote about their advancing conditions with great poignancy and insight.

Shenk isn't afraid to be fascinated by his subject, to evince wonder at the mind's awesome complexity even while chronicling its deterioration. Like Jonathan Swift, he shuttles between the very small and very big: from the molecular level at which Alzheimer's research is done to the overwhelming consequences that threaten the industrialized nations if that research doesn't pan out.

Consider the demographics. In the U.S., people over 85 are the fastest-growing segment of the population -- and 30 to 40 percent of people over 85 suffer from Alzheimer's. The average Alzheimer's patient lives eight years after being diagnosed, but this span will probably widen as a healthier, better-fed cohort gets the disease. One in nine baby boomers will live to be 100: All those hours on the Stairmaster could buy you 20 years of looking good, feeling fine and being totally unable to take care of yourself.

They have no Remembrance of anything but what they learned or observed in their Youth and middle Age, and even that is very imperfect ... In talking they forget the common Appellation of Things, and the Names of Persons, even of those who are their nearest Friends and Relatives.

That's how Swift's Lemuel Gulliver described the Struldbruggs, a race whose members live forever but lose their mental faculties in their 80s. Horribly prescient, Swift had witnessed an uncle's memory loss and was sure that the same thing would happen to him. It did.

"They can never amuse themselves with reading, because their Memory will not serve to carry them from the Beginning of a Sentence to the End."

Powerless to help, I watched my mother-in-law struggle to read a newspaper article, her eyes anxiously and repeatedly darting back to the top of the page. Jonathan Swift, I realized, had not only been horribly prescient about the ravages of memory loss; he'd been absolutely, horribly precise.

The medical vocabulary describes Alzheimer's as a disease of "insidious onset." Insidious is a good word for a disease that begins so slowly and stealthily -- "treacherously," my dictionary says. Sufferers don't forget everything at once: long-term memories (like my mother-in-law's disapproval of my easily-stained hall carpeting) may remain untouched for years.

The old memories stick because at first Alzheimer's doesn't hinder memory retrieval. Instead -- like Leonard in the recent film "Memento" -- the Alzheimer's sufferer can't make new memories. Here's how Shenk describes memory formation in the normal brain: "Each notable experience causes a unique set of neurons to fire in conjunction with one another. As a result, these connections become chemically more sensitive to one another so they can more easily trigger each other again. With that unique constellation of synapses, one has created a permanent physical trace of the original sensation."

A memory is a physical trace, but not like the linear procession of ones and zeros marching across my hard disk as I type this. Memory is branching, multidimensional, a dense web of association and combination. Shenk reminds us that Memory was the mother of the muses -- as though the arts had derived their multiplicity of techniques from her.

Next page: The prospect of millions of octogenarian boomers