Chalk it up to the power of suggestion or a self-inflicted case of "medical student syndrome," but ever since reading Carved in Sand, I can't shake the feeling that I may be suffering from a mild case of neurasthenia.

For those of you who didn't read last week's review, neurasthenia is a term coined in 1869 by neurologist George Miller Beard to describe a range of symptoms plaguing people at the turn of the last century. Beard found that many of his patients were suffering from: "fatigue, anxiety, headache, neuralgia [chronic pain of the nerves], depression . . . weakness, dizziness, and fainting." This may sound like the typical wear and tear of everyday life to you and me, but Beard thought different. He believed it was a result of the "stresses of urbanization." Neurasthenia, in Beard's view, was the psychic price tag for rapid change.

So? Think about it. All those cats had to cope with was railroads and the telephone. We are in the throws of redefining what it means to be human. As V.S. Ramachandran said in his first Reith Lecture: "We are poised for the greatest revolution of all - understanding the human brain . . . [and unlike] earlier revolutions in science, this one is not about the outside world, not about cosmology or biology or physics, but about ourselves, about the very organ that made those earlier revolutions possible." Anyone trying to keep pace with the barrage of breakthroughs in neuroscience can attest to this. And this constant reinvention is both fascinating . . . and exhausting.

Think I'm overstating the case? Here are just a few of the the plate-tectonic shifts that have occurred in our understanding of the human brain this week:

*"Brandeis University researchers report for the first time that memory storage can be . . . biochemically erased. . . by manipulating a so-called "memory molecule," a protein kinase known as CaMKI."

*Researchers at the Chinese Academy of Sciences may have discovered what separates men from apes. A gene mutation "expressed only in the central nervous systems of humans . . . that originated less than 5 million years ago."

*Scientists at the University of Wisconsin-Madison have found a way to induce deep sleep at will, theoretically making it possible to "magnetically stimulate power naps which might confer the benefit of eight hours [of] sleep in just a few hours."

Lordy.