BRAIN PLASTICITY

I was disappointed and more than a little angry to find prevention or treatment of autism listed among the uses of new discoveries in neuroplasticity in the otherwise excellent “The Power of the Infant Brain,” by Takao K. Hensch. Ironically, in his last paragraph, Hensch brings up a parallel to one of the main objections to such “cure” rhetoric: it represents a neurological change so pervasive as to violate the identity of the treated person. Unlike schizophrenia or amblyopia, autism is not separable from the selfhood of those who have it. Furthermore, such rhetoric promotes incredibly harmful Pavlovian “corrective therapies,” such as certain forms of applied behavior analysis.

I am autistic, I've met with and listened to speeches and read essays by dozens of other autistic people, and I can assure you that we do not in fact want to be “cured.”

PAUL EISEN
via e-mail

Hensch expresses concern that “the rewiring of the brain could threaten to undermine one's sense of self.” I do not understand why he views undermining one's sense of self negatively. “Self” is an overvalued, arbitrary human construct. Much has been written about its undesirability in Buddhist philosophy. That outlook goes quite well with his own statement about meditation increasing plasticity and thereby undermining the fixed sense of self.

PREVESH RUSTAGI
Fort Wayne, Ind.

BENIGN MICROBES

In “Bitter Taste Bodyguards,” Robert J. Lee and Noam A. Cohen refer to “modern society's excessive use of antibiotics” and its many negative consequences. Yet the article is full of references to “invaders” of the body and the need to kill these sources of harm.

Surely, our communal failure to understand and value the symbiotic relationship we have with the overwhelming number of microbes in our environment leads us to do things like buy antibacterial wipes for every household surface and wage continuous war against what in many cases is helpful to us.

It might be a good policy to add some language in any article on disease and infection to the effect that, amid the many beneficial interactions we have with the microbes we are embedded with, the article deals with a harmful interaction.

ED AND DENISE MCCAFFREY
via e-mail

SHOEMAKER-LEVY 9

I enjoyed David H. Levy's retrospective on his lifelong quest for comets [“My Life as a Comet Hunter”]. In late March of 1993, before Levy became an astronomy celebrity, he was scheduled to give a presentation at the Phoenix Astronomical Society in Arizona, where he was a regular speaker.

Levy arrived a few minutes late, waving an envelope and saying, “I hope you don't mind if I change the topic of my talk, but I have something here I think you'll want to see.”

I was in charge of A/V at the time, which was still pretty much slides, film or overhead transparencies. While Levy was setting up in the front of the room, he removed a print from the envelope and asked if it could be projected. I explained that we had an opaque projector we could use, but the print would need to be covered by a glass plate to hold it flat under the 200-watt bulb. He expressed some concerns about damage but relented.

The photograph survived fine. It clearly showed the “string of pearls” Comet Shoemaker-Levy 9 on its way in to Jupiter. Levy gave his revised talk, noting that the NASA Jet Propulsion Laboratory had suggested a distinct possibility of impact. The rest is history.

DAN HEIM
President, Desert Foothills
Astronomy Club

PRENATAL SCREENING

“Beware Prenatal Gene Screens,” by the Editors [Science Agenda], highlights the growing role of noninvasive prenatal tests in helping women, with the aid of their physicians, assess their fetus's risk for genetic disease in pregnancy and cautions that such assessments have a higher chance of false positive results than more specialized diagnostic exams do.

Like all clinical tests, noninvasive prenatal tests have limitations. That is why Quest Diagnostics is collaborating with the Perinatal Quality Foundation to create a registry to track false positives and false negatives and to educate women and physicians in the appropriate use of these tests.

Quest has purposefully adopted the phrase “noninvasive prenatal screening” to emphasize that this is a screening test whose positive result should receive “diagnostic” confirmation.

DOUGLAS S. RABIN
Medical director, Women's Health,
Quest Diagnostics

HIDDEN PLANET

In “The Search for Planet X,” Michael D. Lemonick notes that the strange orbital paths of about a dozen objects (including an ice ball named Sedna) are consistent with this system of objects being perturbed in their orbits by an unknown additional planet—a super Earth (a planet roughly up to 10 times the mass of Earth)—in the remote regions of our solar system. If these orbits can be analyzed to reveal where the source of the perturbation lies, then it may be possible to find this “Planet X.”

Some man-made objects may be getting perturbed as well. Pioneer 10, launched decades ago and now well beyond Pluto, has slowed down more than expected. It's an anomaly with no agreed- on explanation. If Planet X is causing this slowing, could Pioneer be added to the other objects to help find Planet X?

DAVID HOWELL
Alton, N.H.

Dear Planetary Scientists,
How cruel you were to cast me out
And leave me moaning in disgrace.
I beg you: don't compound the pain—
Don't put another in my place.
Yours truly,
Pluto

C/O FELICIA NIMUE ACKERMAN
Professor of philosophy,
Brown University

LEMONICK REPLIES: In response to Howell's question: Both the Pioneer 10 and 11 missions slowed excessively on their way out of the solar system. The widely accepted solution to that anomaly is that it was caused by heat emissions from their onboard power supply and instruments. In principle, gravity from an unknown planet could have at least been an influence. In practice, however, the best estimate for the mass and location of the proposed Planet X would make its gravity too weak to account for the slowdown.

ERRATA

“The Search for Planet X,” by Michael D. Lemonick, referred to the icy body Sedna as 2,250 kilometers across. That was an early estimate. The figure has since been revised to about 1,000 kilometers. Further, the article gave the distance of the Nemesis star proposed by physicist Richard Muller in the 1980s as “10,000 AU, or about 1.5 light-years.” The former figure should have been 100,000 AU.

In the “Periodic Table of Substitute Availability” illustration in “Elemental Urgency,” by Jennifer Hackett [Advances], the element thallium was incorrectly given the symbol “Ti.” It should have read “Tl.”