SCIENCE NEWS This Week Attention Loss ADHD may lower volume of brain

Youngsters diagnosed with attentiondeficit hyperactivity disorder (ADHD) lack con- centration, patience, and organizational skills. A new study reveals that the brains of these children are slightly smaller than those of their peers who are free of psychi- atric disorders.

This disparity is most pronounced for the children and teenagers with ADHD who have never taken a stimulant medication, such as Ritalin, say psychiatrist F. Xavier Castellanos of New York University and his colleagues.

Overall, kids with ADHD had total brain volumes about 3 percent less than those of unaffected youngsters. Brain development followed parallel paths for participants with and without ADHD, but the 3 percent dis- parity in brain volume stayed constant.

Never-medicated children with ADHD also exhibited smaller white-matter volume inthebrainthandidboththosetakingstim- ulants and those free of mental ailments. White matter, which grows thicker as a child matures, consists of fibers that estab- lish long-distance neural connections.

“It’s possible that stimulant medication promotes brain maturation,” Castellanos says.

Although there are valid concerns about the risks oflong-term stimulant use, choos- ing not to use medication may present its own risk, adds study coauthor Jay N. Giedd, a psychiatrist at the National Institute of Mental Health in Bethesda, Md. “The new findings make treatment decisions even tougher,” he says.

The scientists present their findings in the Oct. 9 Journal of theAmerican Medical Associatim.

The team used magnetic resonance imaging (MRI) devices to measure brain volumes in 89 boys and 63 girls with ADHD-of whom, 103 were on medica- tion-and 83 boys and 56 girls without any

psychiatric conditions. Participants ranged in age from 5 to 18 years at the start of the study. Over the next decade, a majority of them underwent at least one, and as many as three, more MRI scans.

The data reveal that several discrete brain areas were smaller in children with the most severe forms of ADHD symptoms, which include inattention, hyperactivity, and impulsiveness, than in kids displaying milder versions. These areas consisted of parts of the frontal and temporal lobes, the inner-brain region known as the caudate nucleus, and the cerebellum. Earlier, smaller MRI studies had primarily impli- cated the frontal lobe in ADHD.

ADHD appears to stem from genetic variation in brain size rather than a brain defect, Giedd proposes. Any of several bio- logical processes occurring in a slightly undersized brain may contribute to impulsiveness and hyperactivity, which often play out most dramatically at school, he theorizes.

“This study provides a new look at the developing brain in ADHD,” remarks psy- chologist Carl M. Anderson of McLean Hospital in Belmont, Mass. Of particular interest is the possible role of the cerebel- lum in ADHD, he says. Research now sug- gests that this rear-brain structure, which is usually associated with coordinating motion and balance, aids in coordinating thoughts and emotions, according to Anderson.

While rating the new work on ADHD as the most rigorous to date, psychologist Alan A. Baumehr of Louisiana State University in Baton Rouge says the hdings need to be replicated in independent studies. It remains unclear, he says, whether a discrepancy in brainskspecifidyunderliesADHDoralso chamcteriz.es childhood depression and other mental disorders. -6. BOWER

Physics for Sale Collectors snap u pricey historical materia P s

Want a glimpse Of Albert Einstein’s mind at work? Lastweek, it cost abuyer $559,500.

An unprecedented sale of manuscripts, books, and reports documenting the devel- opment of modern physics took place at Christie’s auction house in New York on Oct. 4. It brought in nearly $1.8 million. The highest-selling documents were those attributed to the most famous physicists, with 8 of the top 10 written by Einstein.

The half-million-dollar centerpiece of the Harvey Plotnick Library, named for the man who collected the items, was a hand- written 1913 manuscript by Einstein and his colleague Michele Besso.

Using early versions of Einstein’s general

theory of relativity, Einstein and Besso unsuccessfully struggled with an anomaly in Mercury‘s motion that’s not explicable with Issac Newton’s theory of gravitation. The manuscript contains more than 50 pages of calculations.

“It’s a snapshot of Einstein’s thinking process,” says Francis Wahlgren, head of the books and manuscripts department at Christie’s in New York. The Einstein-Besso document is one of only two existing works-in-progress showing how Einstein developed the general theory of relativity. The other, the Zurich Notebook, is in the Einstein Archives at Hebrew University in Jerusalem.

“I can’t say that the average collector can read it and see into the mind of Einstein,” says Spencer Weart, the director of the Cen- ter for History of Physics at the American Institute of Physics in College Park, Md. But whether you are a physicist or not, says Weart, “you can feel that what you’re hold- ing is a genuine representation of the cre- ative process of what may count as the most amazing scientific discovery of all time.”

One of the few pre-20th-century physi- cists represented in the sale was Newton, whose gravitational theory Einstein improved upon with the general theory of relativity. Newton came in second on the list of top sellers: A small scrap of manu- script added to the second English edition of his Opticks, published in 1717, sold for $89,625.

Rounding out the top three, a copy of Einstein’s 1916 book on the general theory of relativity sold for $83,650. This partic-

W W W . S C I E N C E N E W S . O R G O C T O B E R 1 2 , 2 0 0 2 VOL. 1 6 2 227

- SCIENCE - NEWS This Week

ular volume was marked up by the Nobel laureate Wolfgang Pauli, who, as a teenager, used it to teach himself general relativity. ’You see the mind of one person trying to comprehend the mind of another person,” says Weart.

The entire sale, “says something about the acceptance of science as a cultural ele- ment, not just as something of practical value,” adds Weart. “It points out that peo- ple see a work of science in the way they would see a great painting or a bone of an ancestor."-^. GORMAN

Hefty Discovery Finding a Kuiper belt king - A newly discovered celestial body appears to be the largest object that scientists have found in the solar system since their detec- tion of Pluto in 1930. Designated 2002 LM60, it’s unofficially known as Quaoar (pronounced Kwa-whar) after a Native American god.

Residing in the Kuiper belt, the reservoir of comets and other frozen bodies beyond the orbit of Neptune, Quaoar measures 1,300 kilometers in diameter, more than halfthe width of Pluto. Along with the find- ing of several other Kuiper belt behemoths over the past 2 years, the discovery suggests the region may harbor even larger bodies.

Michael E. Brown and Chadwick A. Tru- jillo of the California Institute of Technol- ogy in Pasadena reported Quaoar’s discov- ery this week at the annual meeting of the

American Astronomical Society’s Division for Planetary Sciences in Birmingham, Ala

Brown and Thjillo found Quaoar on an image taken June 4 with a 48-inch tele- scope at Palomar Observatory near Escon- dido, Calif. Looking through archival images recorded at Palomar, the scientists also identified Quaoar in images from W82, 1996,2000, and 2001. Because they could trace the path of the body over a ao-year period, the astronomers were able to deter- mine Quaoar’s orbit and distance from Earth. The researchers then made further observations with two other detectors, including the Hubble Space Telescope.

Quaoar orbits the sun every 288 years in a near-perfkt circle inclined by 7.9 degrees relative to the plane in which every planet but Pluto travels. Many astronomers now assert that Pluto is itself a Kuiper belt object that got knocked into a highly inclined ellip- tical orbit that crosses the orbit of Neptune (SN: 6/9/01, p . 360). With several large objects now known to belong to the Kuiper belt, Pluto’s size no longer makes the body an oddity in the belt.

“Quaoar definitely hurts the case for Pluto being a planet,” Brown says.

Some astronomers had calculated that another Kuiper belt object, now known as Ixion (SN: 7/21/04 p . 41), is almost as big as Quaoar. But that result is highly uncer- tain, says Ixion codiscoverer Robert L. Mil- lis, director of the Lowell Observatory in Flagstaff, Ark. kdon hasn’t been observed with a telescope, such as Hubble, that could measure its sue directly or with a submil- limeter telescope, which determines the object’s temperature, information that can be used to calculate size. Quaoar, however, was observed with both Hubble and a sub- millimeter telescope.

’Ityo other recently discovered Kuiper belt objects, also observed with submillimeter telescopes, each have a diameter of about goo km.

“It would seem quite likely that there

BIG FIND Quaoar (far right), a newfound giant In the Kuiper belt, alongside (left to rlght) Earth, Earths moon, and Pluto. Thls newly discovered object Is 1,300 kllometers in diameter.

are a few Pluto-sized objects, maybe even Mars-sized objects” that lie farther out than Quaoar in the Kuiper belt, says Brian G. Marsden of the Harvard-Smith- sonian Center for Astrophysics in Cam- bridge, Mass. -R. COWEN

Lawn Agent Cues Embryo Shortfall Herbicide weeds out mice in the womb - Having a lush, dandelion-free lawn may come at an unexpected price. According to a new report, minuscule amounts of over- the-counter weed killers impair reproduc- tion in mice and therefore might also affect other animals, people included.

Previous studies have assessed the toxic- ity of high doses of single herbicide ingre- dients, but they haven’t tested the chemical cocktailstypical ofcommercialformulations, says toxicologist Warren Porter of the Uni- versity of Wisconsin-Madison.

He and his colleagues measured the tox- icity of an unnamed brand of weed-and- feed mix. It included the herbicides 2,4-D, mecoprop, and dicamba-one or more of which is in each of 1,500 commercial weed- killing formulations. Though herbicides tar- get plants, says Porter, many attack basic biological functions common to both plants and animals.

The researchers fed solutions laced with the weed-killing mixture to four groups of laboratory mice throughout their preg- nancies. Concentrations of 2,4-D, for example, ranged from 400 parts per mil- lion parts water in the strongest solution to 0.04 parts per million in the weakest. This weakest concentration is lower than some of those that turn up in the envi- ronment.

The scientists found that compared with mice receiving herbicide-free solutions, herbicide-fed mice had as few as 80 per- cent the number of pups. Surprisingly, mothers exposed to the lowest herbicide doses, in general, produced the smallestlit- ters of mice. The findings are reported in an upcoming Environmental Health Perspec- t i W e S .

Safety tests for chemicals generally start with high exposures and sequen- tially test different groups of animals with lower exposures until few or no toxicity effects are visible. “The dogma is, As the dose goes up, the effect gets worse,” says Fred vom Saal at the University of Mis- 9

However, vom Saal notes, an increas- $ ing body of research shows different pat- 4

souri in Columbia. a

2 2 8 O C T O B E R 1 2 , 2002 V O L . 162 S C I E N C E N E W S