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CONTENTS continued >>

NEWS OF THE WEEK

for Kansas Board Races

More Bang for the Buck

Climate Change Demands Action, Says U.K Report 592

NIH Lends a Hand to Postdocs Seeking to Become 593

Independent Researchers

>> Science Careers story by B Benderly

Quantum Foam After All

Panel Discredits Findings of Tokyo University Team 595

NEWS FOCUS

Fighting Words From WHO’s New Malaria Chief 599

Spending Itself Out of Existence, Whitaker Brings 600

a Field to Life

Laser Points to Bright New Era for Ground-Based Astronomy

Pulsar Sets a Dizzying Standard

Pesky Companions Warp the Milky Way

Snapshots From the Meeting

on Medicinal Chemistry will be held from

6 to 11 August 2006 at Colby Sawyer College, New London, NH The schedules for the

2006 Gordon Research Conferences begin

S H Orkin; T J Martin; L S Kwok

Questions About Forensic Science R Harmon and

B Budowle; G Langenburg; M M Houck; J S Kelly

Response M J Saks and J J Koehler

BOOKS ET AL.

The Convergence of Science and Spirituality

The Dalai Lama, reviewed by E Sternberg

Evolution and the Nature of Narrative

J Gottschall and D S Wilson, Eds., reviewed by H Fromm

POLICY FORUM

M K Cho, G McGee, D Magnus

Community Studies for Vaccinating Schoolchildren 615

Understanding HIV Epidemic Trends in Africa 620

R Hayes and H Weiss

>> Report p 664; Science Express Report by J Stover et al.

Volume 311, Issue 5761

611

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CONTENTS continued >>

SCIENCE EXPRESS

www.sciencexpress.org

EPIDEMIOLOGY

The Global Impact of Scaling-Up HIV/AIDS Prevention Programs

in Low- and Middle-Income Countries

J Stover et al.

Implementation of AIDS prevention measures targeting sexual transmission and drug

users could prevent 30 million new infections in the next 10 years

>> Perspective p 620; Report p 664

10.1126/science.1121176

MEDICINE

BREVIA: Cellular Senescence in Aging Primates

U Herbig, M Ferreira, L Condel, D Carey, J M Sedivy

As baboons age, cells that have become irreversibly senescent accumulate in various

tissues, likely contributing to the aging of the whole animal

10.1126/science.1122446

Late Precambrian Oxygenation; Inception of the Clay Mineral Factory

M Kennedy, M Droser, L M Mayer, D Pevear, D Mrofka

The development of an oxygen-rich atmosphere during the Neoproterozoic was the result

of an increase in the rate of clay deposition caused by the spread of terrestrial vegetation

10.1126/science.1118929

MOSFET-Embedded Microcantilevers for Measuring Deflection inBiomolecular Sensors

G Shekhawat, S.-H Tark, V P Dravid

The small bending created when biomolecules bind to receptors on a microfabricatedcantilever can be detected with an embedded transistor, forming a microsensor

10.1126/science.1122588Exposed Water Ice Deposits on the Surface of Comet Tempel 1

J M Sunshine et al.

Deep Impact has found three patches of water ice on comet Tempel 1, but these are insufficient to account for the water output observed in outgassing,implying a subsurface source

C F E Bacles, A J Lowe, R A Ennos

Dispersal of seeds, rather than pollen, maintains gene flow amongforest remnants for a wind-pollinated, wind-dispersed tree in theScottish Southern Uplands

RESEARCH ARTICLE

NEUROSCIENCENew Neurons Follow the Flow of Cerebrospinal 629

Fluid in the Adult Brain

K Sawamoto et al.

Fluid flow set up by the coordinated beating of cilia along the brain’sventricles carries signaling factors that guide neurons migratingthrough the underlying tissue

REPORTS

ASTRONOMYThe Large-Scale Axisymmetric Magnetic Topology 633

of a Very-Low-Mass Fully Convective Star

E A Stinaff et al.

A combination of electric field resonances and optical excitation cancouple a pair of neutral and charged quantum dots, which can thenexchange quantum-stored information

629

TECHNICAL COMMENT ABSTRACT

ECOLOGY

Comment on “Neutral Ecological Theory Reveals 610

Isolation and Rapid Speciation in a Biodiversity

Toxic Potential of Materials at the Nanolevel 622

A Nel, T Xia, L Mädler, N Li

SUNSHINE et al.

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CONTENTS continued >>

REPORTS CONTINUED

MATERIALS SCIENCE

Plasticization-Enhanced Hydrogen Purification 639

Using Polymeric Membranes

H Lin, E Van Wagner, B D Freeman, L G Toy, R P Gupta

Highly branched, cross-linked polymer membranes can effectively

remove carbon dioxide and hydrogen sulfide during hydrogen

purification, even at high pressures

CHEMISTRY

Asymmetric Hydrogenation of Unfunctionalized, 642

Purely Alkyl-Substituted Olefins

S Bell, B Wüstenberg, S Kaiser, F Menges, T Netscher, A Pfaltz

An iridium catalyst accomplishes the longstanding goal of adding

hydrogen across alkyl-substituted carbon double bonds to generate

homochiral products, a common reaction in organic synthesis

>> Perspective p 619

GEOPHYSICS

Plastic Deformation of MgGeO3Post-Perovskite 644

at Lower Mantle Pressures

S Merkel et al.

Experiments on an analog of a major mineral in Earth’s deepest mantle

imply that alignment of mineral grains by flow could explain observed

seismic signals

GEOPHYSICS

Lubrication of Faults During Earthquakes

G Di Toro, T Hirose, S Nielsen, G Pennacchioni, T Shimamoto

Experiments and analysis on natural faults show that melt produced

by friction during faulting weakens the fault, allowing sliding at

lower stresses

EVOLUTION

Genetic Accommodation

Y Suzuki and F Nijhout

Laboratory selection for tobacco hornworms that change color

when warm produces a polyphenism, in which one genome yields

alternative phenotypes in different environments

>> News story p 591

BIOCHEMISTRY

RNA Adaptation

Q Zhang, X Sun, E D Watt, H M Al-Hashimi

Motions of local and larger domain regions in a regulatory RNA allow it

to take on different conformations, enabling it to bind to diverse targets

SCIENCE (ISSN 0036-8075) is published weekly on Friday, except the last week in December, by the American Association for the Advancement of Science, 1200 New York Avenue, NW, Washington, DC 20005 Periodicals Mail postage (publication No.

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$10.00 per issue prepaid includes surface postage; bulk rates on request Authorization to photocopy material for internal or personal use under circumstances not falling within the fair use provisions of

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222 Rosewood Drive, Danvers, MA 01923 The identification code for Science is 0036-8075/83 $18.00 Science is indexed in the Reader’s Guide to Periodical Literature and in several specialized indexes.

STRUCTURAL BIOLOGY

Activator in Complex with Its Receptor

Q Huai et al.

The structure of a receptor-ligand complex implicated in tumor growthand metastasis may provide a basis for the design of anticancer drugs

ECOLOGY

Instantaneous Continental Shelf–Scale Imaging

N C Makris et al.

A remote-sensing method can detect shoals of fish that are thousands of square kilometers in size, revealing their migration habits and group behavior

EPIDEMIOLOGYHIV Decline Associated with Behavior Change 664

in Eastern Zimbabwe

S Gregson et al.

A decrease in HIV infections in Zimbabwe may reflect a larger trend across sub-Saharan Africa resulting from national programs, condom use, and fear of AIDS

>> Perspective p 620; Science Express Report by J Stover et al.

NEUROSCIENCE

R Rajan, J P Clement, U S Bhalla

Like vision and audition in humans, olfaction in rats is a stereo sense,

in which relative timing and intensity of the stimulus in each nostrilhelps to locate the source of odors

NEUROSCIENCE

Face-Selective Cells

D Y Tsao, W A Freiwald, R B H Tootell, M S Livingstone

All of the neurons within a discrete part of the cortex of the macaquemonkey are activated exclusively by faces

>> Perspective p 617

617 & 670

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SCIENCENOW

www.sciencenow.org DAILY NEWS COVERAGEPrions Present a Positive Side

The "mad cow" proteins also help blood stem cells survive

Cyanobacteria Work the Night Shift

Darkness and extreme heat are no problem for algae convertingnitrogen to nutrients

You've Got What in Your Ears?

A small genetic change determines whether your earwax

is wet or dry

SCIENCE’S STKE

EDITORIAL GUIDE: Focus Issue—Signaling Lipids

N R Gough

Lipids play diverse roles in cell signaling

PERSPECTIVE: Role of Docosahexaenoic Acid in Neuronal

Plasma Membranes

J A Glomset

Small differences in the structures of membrane phosphoglycerides

may have major implications for cell signaling

PERSPECTIVE: Building Signaling Complexes at the Membrane

W Cho

Multiple interactions promote the formation of specific signaling

complexes at cellular membranes

Sit back and learn

Bridging the independence gap

SCIENCE’S SAGE KE

MEETINGS AND EVENTS

Learn about free radicals, innate immunity, cardiac regeneration,

and more at this month's aging-related meetings

Membrane phospholipid diversity

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Figure 1: GFP expression in HEK-293 EBNA cells.

HEK-293 EBNA suspension-adapted cells were transfected

with plasmid DNA for GFP following the recommended

protocol, using ratios of 7:2, 6:2, 5:2, 4:2, and 3:2 (μl FuGENE ®

HD Transfection Reagent:μg plasmid DNA) The percentage

of cells transfected (a) was determined 28 hours post

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the Coomassie Blue-stained gel at 72 hours post transfection.

tum dots where coherent coupling between thedots can be induced by a combination of electricfield resonances and optical excitation The mainspectroscopic features can be recovered with a rel-atively simple molecular model.

Under Pressure to Separate

When hydrogen is produced industrially, the gasstream is typically contaminated with H2S, CO2,steam, and other impurities that need to beremoved Ideally, the separation should occur athigh pressure to avoid costly recompression, butcurrent membrane materials do not work well at

high pressure Lin et al (p 639) have

devel-oped polymeric membrane materials that entially absorbed CO2and other impurities andthat showed greater efficiency as the pressure ofthe gas feed was increased Unlike conventionalmembranes, the presence of impurities plasti-cizes the polymer membranes and improvestheir selectivity and permeability

prefer-Differences Without Diversity

When adapting to varied environments, someplants and animals take on alternative pheno-types but retain the same genotype The classiclaboratory model organism, the tobacco hawk-

moth Manduca sexta, is monophenic with a

green larval phenotype However, the sister

species, the five-spotted hawkmoth M

quin-quemaculata, is polyphenic with a black

phe-notype at 20°C and greenphenotype at 28°C

Suzuki and Nijhout (p

650; see the news story

by Pennisi) sensitized

M sexta to

environmen-Assessing Nanomaterial

Safety

Scenarios of the dangers of nanotechnology that

involve nanorobots running amok in our bodies or

the world being taken over by “gray goo” are

con-sidered highly unlikely by many experts However,

a great deal remains unknown about the biological

effects of human and environmental exposure to

nanomaterials Nel et al (p 622) review the

important chemical and biological properties of

nanomaterials and outline ways in which the safety

and toxicity of these substances can be evaluated

Magnetic Maps

Magnetic fields on stars like the Sun affect their

interiors and their surrounding environment In

strongly convecting stars, turbulence is expected to

break up aligned magnetic fields Donati et al.

(p 633; see the Perspective by Basri) show that in

a very-low-mass, fully-convective star, substantial

fields remain, including a strong dipole

compo-nent The pattern of magnetic fields on the star’s

surface was recreated from observations of the fine

Zeeman splitting of spectral lines caused by

mag-netic fields and other signatures in polarized light

Spectroscopy of Coupled

Quantum Dots

Single and coupled multiple quantum-dot

struc-tures have long been proposed as systems for

storing and manipulating information in

quantum information processing

How-ever, finding routes to get the coupled

dots to communicate are only now being

explored Stinaff et al (p 636, published

online 12 January) present a spectroscopic

study of pairs of neutral and charged

quan-tal temperature by

using a black mutant

line Mutation of the

black gene reduced

juvenile hormone andincreased melanization

of the larval epidermis

Heat shock of the black

mutant generatedlarva with colors rang-ing from black to green Two lines were estab-lished with the desired phenotype (green orblack) by selecting individuals from subse-quent generations of black mutant popula-tions Polyphenism can thus evolve by geneticaccommodation regulated by juvenile hor-mone

Hydrogenation with Less Guidance

The selective addition of hydrogen across carbon double bonds to generate homochiralproducts is used to prepare a wide range of com-pounds, both in the lab and in industry However,the scope of this reaction is often limited by theneed for a specific group adjacent to the olefin,whether a phenyl or a coordinating oxygen or

carbon-nitrogen substituent, to direct the catalyst Bell et

al (p 642, published online 8 December 2005;

see the Perspective by Wills) show that a class ofiridium compounds, coordinated by chiral ligandswith both phosphinite and pyridine groups, cancatalyze the asymmetric hydrogenation of olefinsbearing only simple alkyl substituents Theyreduce a vitamin E precursor at two noncontigu-ous C=C bonds in an alkyl chain with net selectiv-ity exceeding 98%

EDITED BY STELLA HURTLEY AND PHIL SZUROMI

<< Slippery Melt Strands

Some exhumed faults contain small pockets of meltedrocks, presumably produced by frictional heat during anearthquake The role of these melt strands—whether theyinhibit faulting or lubricate it—and how they are produced

in weak faults has been controversial Di Toro et al.

(p 647) have now produced analogous features in the oratory that they compare with actual field samples from anexposed fault They used a rotary shear apparatus to sliderocks against each other at conditions that approximatenatural earthquakes Melt pockets were produced that low-ered the friction and lubricated rather than sealed the fault

lab-Continued on page 575

EDITED BY STELLA HURTLEY AND PHIL SZUROMI

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This Week in Science

Neurons Navigate Downstream

Neurons born near the brain’s ventricles travel out to the olfactory bulb to function in olfaction A

steady stream of migrating neurons makes the journey not only in early development, but also

during adulthood Sawamoto et al (p 629, published online 12 January) now provide insight into

how these neurons find their way in mice The ventricles of the brain are lined with cells bearing cilia

on their surface The coordinated beating of these cilia develops a stream of fluid coursing through

the ventricles carrying signaling factors that guide the traveling neurons Mutations that disrupt the

cilia also disrupt establishment of the signaling gradient and the migration of the neurons to the

olfactory bulb

Flexible RNA

Conformational flexibility of RNA molecules arises from a complex set of local motions, collective

domain motions, and overall rotational diffusion Zhang et al (p 653) describe a

domain-elon-gation strategy that allows them to resolve picosecond local motions and nanosecond domain

motions by nuclear magnetic resonance (NMR) spectroscopy By comparing the structural

dynam-ics to the conformational differences evident in eight HIV-1 transactivation response element

structures, they show that a hierarchical network of local and collective internal motional modes

underlies RNA’s ability to change conformation adaptively

Keeping Tabs on

Schools of Fish

A technology for continuously monitoring fish

populations over areas on the scale of

continen-tal shelves has been developed by Makris et al.

(p 660) that uses the ocean as an acoustic

waveguide Its areal survey rate is several orders

of magnitude greater than that of current survey

methods The technology has been used to

pro-vide instantaneous images of enormous fish

shoals in their entirety, as well as to reveal rapid

temporal and spatial changes in these shoals

HIV Decline in Zimbabwe

The human immunodeficiency virus epidemic in Zimbabwe is slowing down because of a large-scale

change in sexual behavior, particularly among young and educated people Gregson et al (p 664;

see the Perspective by Hayes and Weiss) present an analysis that disentangles decline from the

mor-tality of high-risk subpopulations and a lower infection rate of young people These trends may be

taking place across much of sub-Saharan Africa and seem to result from a combination of national

program activities, condom use, and increased fear of death from AIDS

Smelling in Stereo

Stereo sound localization uses both intensity and phase differences between the ears to determine

source direction Rajan et al (p 666) report that olfaction can use similar cues Trained rats can

locate an odor source to the left or right using concentration differences or time-of-arrival

differ-ences Rats can perform this task within a single sniff Olfactory bulb neuronal responses recorded

in response to directional odor stimuli were highly selective for the direction of odor stimulation

Processing Nothing But Faces

Are there areas in the brain that are solely dedicated to the processing of faces? Tsao et al (p 670;

see the Perspective by Kanwisher) used functional magnetic resonance imaging on monkeys in order

to identify areas responding to faces, and then implanted electrodes in the principal area in order to

identify its properties at the single-cell level In this region, virtually all of the cells only responded to

faces This finding supports the idea that the cortex has a modular architecture

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Advancing the Frontiers

THERE HAS BEEN MUCH DISCUSSION RECENTLY ABOUT WAYS TO STIMULATE MORE “HIGH-RISK–

high-payoff” research: projects that have the potential to make major leaps in scientific understanding

In the United States, the National Science Board, for example, has had a task force dedicated to thisissue for over a year, and the National Institutes of Health’s Roadmap includes efforts to transformfundamental and clinical biomedical research

One approach to advancing these frontiers has proven quite successful over the years It is the modelused by the Gordon Research Conferences (GRCs), which this year celebrate their 75th anniversary;

their 2006 program appears in this issue of Science The GRCs, which began in 1931 as a chemistry

meeting conceived and organized by Neil Gordon, now encompass some 180 conferences each year at

17 different sites in the United States and abroad Over 20,000 international scientists will participate inthese intense meetings that span the whole spectrum of science, science education, and science policy

The American Association for the Advancement of Science (AAAS) has had a close association withthe GRCs since 1938, when it took over managing the conferences—an arrangement that lasted until

1956, when the GRCs became independent

A fascinating compendium* of personal reminiscences about the ferences and their scientific impacts, contributed by a diverse group of

con-80 well-respected scientists, reveals why these conferences are so popularand successful and why they have persisted on a regular basis for so long

Reduced to its core, the success of these meetings amounts to the way inwhich their format has promoted transformative thinking and projectdevelopment Maxine Singer, for example, writes about the importance of the

1973 Nucleic Acids meeting in stimulating thinking about the implications ofrecombinant DNA (cloning) experiments Other authors cite the central role

of the GRCs in the emergence of such multidisciplinary fields as bioinorganicchemistry, organic electronics, and mammary gland biology

A core lesson from the GRCs is that even in this age of electronic communicationtechnologies, there is no substitute for putting a small group of people together face to face andkeeping them in close contact for a few days The relatively isolated sites used for the GRCs and thefact that each conference is usually restricted to about 100 attendees encourages people to talk to eachother with both informality and candor And the conference agenda allows for plenty of unstructureddiscussion time and promotes long conversations about frontier science

Many of the important unanswered scientific questions are multidisciplinary in character This

feature of contemporary research was amply demonstrated in Science’s 2005 list of the top 25 questions

for the next 25 years.† To promote the kind of thinking needed for problem-based rather than based science, one needs to bring experts together from all potentially relevant fields and create anenvironment in which they may speak freely and frankly with one another That is exactly the kind ofconversation that GRC attendees are engaged in All discussions are off the record, and all conferencecommunications are considered private This fosters safe spaces for posing “risky” ideas and engaging

discipline-in creative and occasionally speculative communal thdiscipline-inkdiscipline-ing As Norman Hackerman emphasizes discipline-inthe GRC compendium, “The greatest advantage of these meetings was that attendees were able toparticipate without worrying about being proved wrong in publication ” On the nonhierarchicalnature of the meetings, Roy Vagelos reflects, “There I was [at his first Lipid Metabolism conference],

a pipsqueak only a few years out of a postdoctoral fellowship, speaking alongside these giants ofbiochemistry.” Not surprisingly, some of the giants later became Vagelos’ collaborators

The GRCs are only one way to encourage transformative thinking and research, but their trackrecord suggests that we may need more venues like them Scientists sometimes lament that peerreview may be biased in favor of cautious and “safe” research, unsupportive of departures frommainstream thinking By creating a relatively unthreatening, unconstrained atmosphere, the GRCsprovide a refreshing opportunity to try out new ideas on one’s colleagues, brainstorm about difficultand complex issues, and think about possible solutions Not a bad strategy at all

–Alan I Leshner10.1126/science.1125130

*Reflections from the Frontiers, Explorations for the Future: Gordon Research Conferences, 1931–2006, A A Daemmrich,

N R Gray, L Shaper, Eds (Chemical Heritage Press, Philadelphia, PA, 2006) †Science 309, 75 (2005).

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analyzed with classical cytogenetic techniques,yielding evidence of a complex rearrangementinvolving chromosomes 6, 9, 11, and 20 Later,the mother carried a fetus to term; the adultdaughter was determined to carry the samerearrangement and, like the mother, displayedmodest levels of the fetal form of hemoglobin[hereditary persistence of fetal hemoglobin(HPFH)].

Fauth et al have used multiplex fluorescence

in situ hybridization and DNA microarrays tomap the precise nature of the rearrangements

They find that the derivative chromosome 6[referred to as der(6)] possessed by mother anddaughter contains portions of chromosomes

Regulating Food Intake

The kakapo—a bulky, ground-dwelling parrot

endemic to New Zealand—is one of the world’s

most endangered birds, with just 83 living

individuals For the past 15 years, conservationists

have attempted to increase the population by the

supplementary feeding of female birds However,

although ad libitum feeding has indeed improved chick

survival, it has also changed the sex ratio of offspring

hatched, so that 70% of chicks are male: a proportion clearly

at odds with conservation objectives

Offspring sex ratio is known to be affected by

environ-mental factors and maternal conditions in predictable ways;

in particular, females in good condition tend to produce

more sons Robertson et al have recently achieved

near-parity in offspring sex ratio by regulating the amount of

supplementary food given to females as a function of their

predicted weight; feeding could not be abandoned entirely,because female kakapo need to weigh more than 1.5 kg inorder to breed at all Thus, the prospects for a conservationprogram have been enhanced by the application of theoryfrom evolutionary biology — AMS

Biol Lett 10/1098/rsbl.2005.0430 (2006).

A P P L I E D P H Y S I C S

THz in Practice

Terahertz (THz) radiation penetrates cloth and

plastic to a degree that scales inversely with the

frequency Solid-state laser sources, such as

quan-tum cascade lasers, have been fabricated with

energy-level separations tuned for emission

toward the high end of the THz regime However,

efforts to lower the frequency, and thereby

improve penetration, have been hindered by

scat-tering problems and by reduced out-coupling

effi-ciency as the energy-level spacing approaches the

emission linewidth

Worral et al demonstrate a superlattice

quan-tum cascade laser that emits 2-THz continuous

wave radiation at an operating temperature of 47

K They accessed this low-frequency region in part

by precise modulation of the aluminum doping

level in the GaAs/AlGaAs lasing medium The

result suggests that the emission frequency

might be reduced further by careful control of

the fabrication and design process — ISO

Opt Exp 14, 171 (2006).

G E N E T I C S

A Familial Four-Way Swap Fest

Qualitative advances in technology have made

it possible to reexamine an old case, which has

led to a heightened appreciation of the fidelity

of chromosomal segregation Over 2 decades

ago, a patient with a history of miscarriage was

(chrs) 11 and 20, der(11) carries bits of chrs 6and 9, der(20) contains portions of chrs 6 and

11, and der(9) harbors multiple pieces fromchrs 6 and 11, adding up to a total of 12 breakpoints (one of which coincides with aquantitative trait locus for HPFH) spread overfour chromosomes Nevertheless, theserearranged chromosomes pass faithfullythrough the pachytene stage of meiosis, whenhomologous chromosomes pair and form bivalents — GJC

Hum Genet 10.1007/s00439-005-0103-z (2006).

I M M U N O L O G Y

Primed by Parasites

Collectively, parasites belonging to the genus

Leishmania cause extensive mortality and

mor-bidity around the globe Two major forms ofleishmaniasis are characterized by distinctpathologies: a life-threatening visceral diseaseand a cutaneous form, involving self-healingskin ulcerations In the latter, residentmacrophages and dendritic cells (DCs) of theskin take up the parasite, although in DCs thisleads to the priming of Th1 cells that ultimatelyresolve the disease

Woelbing et al show that unlike

macro-phages, which use the complement receptor to

bind and phagocytose Leishmania promastigotes,

DCs acquire the parasite through Fc receptor(FcR)–mediated uptake of complexes comprising

EDITED BY GILBERT CHIN

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antibodies to Leishmania bound to parasitic

amastigotes Without B cells, normally resistant

mice became susceptible to disease, as did

ani-mals genetically lacking the relevant FcR for IgG

binding In both cases, disease susceptibility

was directly attributable to a failure of DCs to

prime T cells efficiently and, consequently, to

reduced production of IFN-γ This pivotal role

for antibodies to parasites in the priming of T

cell immunity by DCs raises the interesting

question of how the initial B cell response to

the parasite itself develops — SJS

J Exp Med 10.1084/jem.20052288 (2006).

C H E M I S T R Y

and in Theory

Terahertz (Thz) radiation, which bridges the

infrared and microwave regions of the

electro-magnetic spectrum, can penetrate most

cloth-ing and packagcloth-ing materials Researchers have

therefore sought to develop THz spectroscopy

for security screening, which would require a

precise understanding of the absorption

spec-tra that would signal the presence of drugs or

explosives However, the spectra are hard to

analyze because they comprise many

overlap-ping modes, arising both from intramolecular

vibrations and delocalized lattice motion

One approach has been to model the

individual molecules computationally, as

though they were in the gas phase, in order to

discern which spectral features correspond to

intramolecular modes, but

Allis et al uncover a

prob-lem with this method

Using several variants of densityfunctional theory, theysimulate the THz

absorption spectrum of crystalline HMX

explo-sive, a solid composed of eight-membered

rings with alternating CH2and N(NO2) groups

Modeling of the isolated molecule fails to

reproduce any of the experimental absorption

features, whereas more computationally

demanding methods, which treat the extended

solid lattice, yield reasonable agreement with

the measured spectrum The results suggest

that packing forces in the lattice shift the

ori-entation of NO2substituents and thereby affect

intramolecular mode frequencies in addition to

lattice modes — JSY

J Phys Chem A 10.1021/jp0554285 (2006).

B I O M A T E R I A L S

Mixing and Matching

Strategies for spinal cord injury repair may benefit

if a more controlled delivery of drugs to the site ofthe wound can be achieved Although bolus injec-tion or a minipump can be used, with the former,the drug may wash away, and a catheter maybecome blocked or infected One approach would

be to encase the drug in a biodegradable gel thathas a viscosity low enough for injection and thatgels fast enough to localize to the wound, whilebeing biocompatible and nonadhesive

Gupta et al have designed such a material by

combining methylcellulose (MC) and hyaluronan(HA) HA is known to promote wound healing byreducing inflammation and minimizing tissueadhesion However, it is highly soluble in waterand disperses when injected into fluid-filled cavi-ties MC has inverse gelling properties—that is, itgels as the temperature rises by breaking poly-mer-solvent bonds and forming hydrophobicjunctions A mixture of 2% HA and 7% MC had alow viscosity and showed fast gelling and suitabledegradation characteristics Intrathecal injection

in rats showed that the gel performed as well as orbetter than artificial cerebrospinal fluid — MSL

Ikeda et al have studied three families

afflicted with spinocerebellar ataxia type 5 (SCA5),

a dominantly inherited neurodegenerative order characterized by uncoordinated gait andslurred speech Affected individuals were found to

dis-have mutations in the SPTBN2 gene, which

encodesβ-III spectrin, a cytoskeletal protein that

is expressed in Purkinje cells, which are markedlydepleted in the brains of individuals with SCA5 β-III spectrin has been implicated previously in pro-tein trafficking, and the mutations may disrupttransport of the neurotransmitter glutamate Ofhistorical interest, one of the families studied was

an 11-generation kindred descended from thepaternal grandparents of President Abraham Lin-coln Whether he inherited the SCA5 mutation isunknown, but this discovery may reignite discus-sions on the ethics of analyzing his DNA — PAK

Nat Genet 10.1038/ng1728 (2006).

Continued from page 579

Calculated geometries

of HMX: gas-phase (red)and solid-state (blue)

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3 FEBRUARY 2006 VOL 311 SCIENCE www.sciencemag.org584

John I Brauman, Chair, Stanford Univ.

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Robert May, Univ of Oxford

Marcia McNutt, Monterey Bay Aquarium Research Inst.

Linda Partridge, Univ College London

Vera C Rubin, Carnegie Institution of Washington

Christopher R Somerville, Carnegie Institution

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CREDITS (TOP TO BOTTOM): RODOLFO GONZALEZ AND JEANNE LORING; USGS; ANDREW R ODUM/PETER ARNOLD INC.

NETWATCH

W E B L O G S

Opinion Buffet

Craving a discussion of the greatest physics experiments

of all time? Hungry to know how computer-generated animation can more realistically depict emotions?

Tuck into this new blog smorgasbord from Seed magazine

The site serves up 15 scientific and science-related columns

on topics as diverse as research ethics, evolutionary biology,and disease Contributors include a cognitive scientist andher husband, a tenure-track physicist, and a former Senatestaffer with a Ph.D in geophysics >> scienceblogs.com

R E S O U R C E S

<< Quaking ‘Round the ClockThis newly upgraded seismic monitoring site from the U.S Geological Survey (USGS) will shorten the delay forobtaining earthquake data USGS’s National EarthquakeCenter now has researchers on duty around the clock tohelp speed measurements to the Web Before, impatientusers sometimes had to wait up to 2 hours after a quake toview online reports, but now information on temblors anywhere

in the world will post within 30 minutes, says Webmaster LisaWald Click on U.S or global maps to find out the depth, strength, andlocation for events within the past week Other report features includeseismic hazard maps that indicate the peak ground acceleration duringthe quake Visitors can dig up plenty of other information on recent and historic quakes This shake map (above), for instance, depicts themaximum ground velocity after a magnitude 3.3 temblor last month near Victoria, Canada.>> earthquake.usgs.gov

R E S O U R C E S

Mammals in Print

Since 1969, the American Society of Mammalogists has published 20 to

30 species accounts each year that cover taxonomy, anatomy, ecology,

and other aspects of the animals’ biology At this site from series editor

Virginia Hayssen of Smith College in Northampton, Massachusetts, you can

download PDFs of these definitive references for more than 700 species

The animals featured include the snow leopard (Uncia uncia) of central

Asia and the naked mole rat (Heterocephalus glaber; right) of eastern

Africa, which dwells in colonies similar to those of bees and ants >>

Tracing Genetic Wrongdoers

Geneticists have pinpointed the genes responsible for diseases such as cystic fibrosis,but for other illnesses, researchers only know the chromosome region where the genelurks GeneSeeker from Radboud University in Nijmegen, Netherlands, can help narrow the list of potential culprits The search engine combs 10 databases that containinformation on gene location, activity, and effects, including Online Mendelian Inheritance in Man, Swiss-Prot, and the Mouse Genome Database Users pick achromosome location linked to a condition, such as cataracts or cleft palate, and thenspecify an organ or structure in which the gene should be active The results list genesthat match the criteria, along with near misses, such as genes that fall in the right regionbut don’t show the correct expression pattern >> www.cmbi.ru.nl/GeneSeeker/

C O M M U N I T Y S I T E

STEM CELL CENTRAL

Human embryonic stem cells excite researchers

because they can theoretically diversify into any

tissue in the body But the existing stem cell lines

were grown under a variety of conditions—some

came from frozen embryos, some didn’t, for

instance—that could affect their performance

Researchers can nab up-to-date information on

available lines at the Stem Cell Community, a

year-old site from the Burnham Institute in San

Diego, California After completing the free

registration, visitors can scan a database that

describes more than 240 stem cell lines, including

53 approved for study with U.S government

funds Users will find information such as where

the cells came from, what protein markers they

sport, whether they’ve ever been frozen, and

whether they were nurtured with mouse feeder

cells Site co-curator Jeanne Loring says that to

fill out the cell portraits, she and her colleagues

are gathering microarray measurements of gene

activity, data on genetic variability, and other

information The site also includes a Community

Information section where you can track down

courses on rearing stem cells or peruse a news

archive.>> www.stemcellcommunity.org

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E D I T E D B Y C O N S T A N C E H O L D E N

Large congregations of vultures are once again appearing in the western Indian

state of Rajasthan—a welcome sight after a precipitous, decade-long decline,

allegedly from poisoning by an anti-inflammatory drug ingested from dead cattle

(Science, 8 October 2004, p 223) Conservationists in India have been clamoring

for a phaseout of the sale of the drug, diclofenac, for veterinary use Vibhu Prakash,

head of the Vulture Care Centre at Chandigarh, says large new populations of

griffon vultures, apparently migrants from Europe and Mongolia, do not appear to

be affected yet, but he believes “it is merely a matter of time.”

But scientists led by zoologist Rhys E Green of Cambridge University in the

U.K say there may be a way out They gave 35 captive-bred vultures in South

Africa and India meat laden with a different anti-inflammatory drug, meloxicam,

available for use in cattle In the March issue of PLoS Biology, they report that the

drug appears to be safe for vultures

VULTURE CULTURE

Eurasian griffon vultures

Scientists have long debated just when canines and people

started being such great chums Most genetics-based estimates

indicate that the domestic dog line split from its predecessor, the

gray wolf, sometime between 15,000 and 40,000 years ago

Darcy Morey, an archaeologist at the University of Kansas

in Lawrence, argues that dog burials are a much better indicator

of domestication Morey combed the literature for evidence

of ancient dog graves and identified more than 50 sites

where dogs were buried singly, in packs, or even cuddled up

with people The est known dog burial,14,000 years old, was

earli-in Germany; others,

in Siberia, date back10,650 years, Moreyreports in the February

issue of the Journal of

Archaeological Science.

The earliest North ican site, at Koster, Illinois, is 8500 years old

Amer-Morey concludes that domestication most likely began

about 14,000 years ago Simon Davis, a zooarchaeologist at

the Portuguese Institute of Archaeology in Lisbon, is convinced

DNA studies may tell us when doggy ancestors split from the

wolf line, he says, but not when faithful mutts started curling

up by the campfire

Carles Vilà, a geneticist and evolutionary biologist at Uppsala

University in Sweden, agrees that “genetic divergence is not the

same as domestication,” but he suspects that dogs were tamed

long before they started being ceremonially interred Morey

disagrees, saying the “essence” of domestication is “a social

relationship that is clearly signified” by the burials

FROM PREDATOR TO PAL

Most people agree that a sense of humor is desirable in a mate But

a study in the January issue of Evolution and Human Behavior

indi-cates that women find this trait much more important than do men.Evolutionary psychologist Eric Bressler of Westfield StateCollege in Massachusetts and behavioral ecologist Sigal Balshine

of McMaster University in Hamilton, Canada, showed 210 graduates, 105 of each sex, photos of

under-two equally attractive members of theopposite sex along with eight statementssupposedly made by each For one, all eight statements were not amusing(“Every year I go to a cabin that my uncleowns, and I go cross-country skiing”)

For the other, three were humorous (“I like the lottery because it’s basically

a tax on people who are bad at math”),and five were not Students were asked torate the two subjects on characteristicssuch as intelligence, trustworthiness,and romantic desirability

Female students overwhelmingly deemed the humorous malesmore desirable But the males were not swayed either way by funnywomen Evolutionary psychologist Geoffrey Miller of the University

of New Mexico in Albuquerque says humor is “a hard-to-fake indicator of several important traits: intelligence, creativity, andmental health.” But for many men, who are more visually oriented

in matters of sex, he says, beauty still trumps wit

Desirable catch?

5000-year-old Kentucky burial

MAKE HER LAUGH

Lava and ice couldn’t be farther apart on the thermal spectrum, but when it comes to carving up mountains, the two have a lot in common.

In the 20 January issue of Physical Review Letters, researchers show

that—during a 2001 volcanic eruption on Sicily’s Mount Etna—

lava carved a channel

6 meters deep in a mere

12 hours That’s far too fast for the gully to have melted, meaning the lava plowed its way through the rock much

as a glacier would The researchers say the results may provide new understanding of how ancient lava flows dug the large channels on Venus and the moon.

Fire and Ice

Lava channel on Mount Etna

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NEWS >>

hornworm turns Getting up the energy for research

3 FEBRUARY 2006 VOL 311 SCIENCE www.sciencemag.org

LAWRENCE, KANSAS—Billboards touting

everything from steak to flat-screen TVs

assault drivers speeding along I-35 across the

American Midwest But an unusual sales pitch

pokes out of the ground just as the interstate

leaves Missouri and enters Kansas “Evolution

is a fairy tale for grown-ups,” the sign

pro-claims, steering viewers to a Web site that

mocks the idea that evolution can explain the

origin of human beings

That Web site (scienceprovesit.com) is a

stark reminder of what scientists and educators

face as they battle new state science standards

casting doubt on evolutionary theory and

effec-tively opening the door to intelligent design

(ID) and creationist instruction in Kansas

pub-lic schools The terms of four of the six-person

majority on the state school board that adopted

those standards 3 months ago end this year, and

defenders of evolution hope voters will choose

moderates in their place who will work to have

those standards thrown out Last weekend, a

rally in Lawrence by Kansas Citizens for Science

(KCFS) served as a de facto kickoff to these

candidates’ campaigns

But moderates hoping to unseat the

incum-bents say a frontal assault on the new standards

would be self-defeating in a state where

conser-vative voters may sympathize with ID even

though they have no appetite for the

fundamen-talist, right-wing groups that have led the

charge against evolution Instead, they plan to

attack other board actions that they believe are

unpopular with voters, including state-funded

vouchers for private schools and a newlyappointed education commissioner whosequalifications have been questioned They alsohope to draw on the recent U.S District Courtruling that threw out ID language inserted bythe Dover, Pennsylvania, school board, callingthe attempt an unconstitutional intrusion of reli-gion into the classroom and ordering it to paywhat are expected to be significant legal fees

“If I were to make the new science dards the focus on my campaign, it’s verylikely that I would lose,” says Harry McDonald,

stan-a former biology testan-acher who is runningagainst incumbent John Bacon, who voted for

the new standards, in the 1 August Republicanprimary Republican Sally Cauble, a formerelementary school science teacher contesting

a seat held by strident ID supporter ConnieMorris, echoes the thought “You have towatch out for that strong undercurrent of sup-

port for faith-basededucation, includingintelligent design,”she says McDonaldand Cauble say theywon’t hide their pro-evolution stance butthat they’d prefer tohave voters raise theissue “It’s not men-tioned in any of mycampaign materials,”says Cauble

Supporters of lution admit grudg-ingly that ID propo-nents have successfullyframed the issue as abattle between scienceand religion “It’s atricky line for the can-didates to navigate,” says KCFS’s Jack Krebs,who spoke at the Lawrence meeting alongsidelawyers representing the Dover parents who pre-

evo-vailed in December (Science, 6 January, p 34).

“Since sophisticated discussions on evolutionand religion are not common in our society,”Krebs says, “it’s very easy for right-wing groups

to brand the challengers as godless atheists.”

A former president of KCFS who now ducts workshops for science teachers and cul-tures butterfly larvae to donate to schools inhis district, McDonald takes care not to comeacross as a passionate evolutionist His litera-ture mentions the new standards as an example

con-of micromanagement by the current board,which took over the writing of the standardslast year after rejecting a draft submitted by thescience standards writing committee “Thereare ID sympathizers in my constituency whomight be willing to forgive me my transgres-sions for being a strong science supporterbecause of other issues But if I spent too muchtime on evolution and ID, they might not.”

Bacon told Science he hasn’t decided

whether to seek reelection to another 4-yearterm But he says that, should he run, he wouldhave no qualms advertising his role in promot-ing the new standards, even though it wouldnot be a centerpiece of his campaign “I’veseen polls showing that the majority of people

in the state want their kids to be exposed to

Strategies Evolve as Candidates

Prepare for Kansas Board Races

SCIENCE EDUCATION

Battlefield Kansas State school board candidate Harry McDonald faces a challenge from antievolution

Legal talk Lawyers for the Dover, Pennsylvania, plaintiffs joined Kansas Citizensfor Science in Lawrence last week in attacking the state’s new science standards

FOCUS Wait a

second 596

When the cash runs out 600

all theories of origin science in the classroom,”

he says “If evolution is a theory, they want it

taught as a theory, not as a fact.”

Both sides agree that, to the extent that

evo-lution gets discussed during the electoral race,

the Dover decision will certainly help the

chal-lengers But John Calvert, the managing

direc-tor of the ID Network in Shawnee Mission,

says it would be unfair to compare the actions

of the two boards “The Kansas standards donot require the teaching of ID in the class-room,” he says “What they do is give teachersthe freedom to answer critical questions aboutevolution without fear of being leaned on.”

Don Weiss, a dean at DeVry University inKansas City and a Democratic challenger whowould face Bacon in November should bothwin their primary races, says he intends to use

the f inancial aspect of the Dover ruling asammunition “Either we can have a ver yexpensive lawsuit, or we can get it taken care ofthrough the election,” Weiss says he’ll tell vot-ers But then he’ll reclaim the high ground

“My broader message is going to be aboutimproving the quality of education in Kansas, sothat our kids can compete in a global economy.”

LOS ALTOS HILLS,

CALIFORNIA—Confound-i n g p r ev CALIFORNIA—Confound-i o u s e s t CALIFORNIA—Confound-i m a t e s , t h e s o - c a l l e d

1 0 t h planet is Pluto’s near-twin in size,

according to a new image from the Hubble

Space Telescope The object is just a “smidge”

bigger than Pluto, not 25% to 50% bigger, an

astronomer reported here last week, and

unusually reflective The downsizing

illus-trates the quandary facing scientists as they try

to define whether large residents of the frigid

Kuiper belt are bona fide planets

Planetary scientist Michael Brown of the

California Institute of Technology (Caltech) in

Pasadena and colleagues found the object,

des-ignated 2003 UB313, as a slow-moving dot of

light It traces an elongated orbit out to its

cur-rent farthest point of 97 times Earth’s distance

from the sun, making it the most remote body

yet seen in our solar system Despite its distance,

the object dubbed “Xena” by Brown’s team

appears so bright that last July NASA described

it as markedly larger than Pluto (Science,

5 August 2005, p 859) But researchers sought

better data to gauge its true size

One new study, published this week in

Nature, favors a chubbier Xena A team led by

radio astronomer Frank Bertoldi of the

Uni-versity of Bonn, Germany, used the IRAM

30-meter radio telescope at Pico Veleta, Spain,

to measure the object’s heat emissions Their

analysis points to a diameter of 3000

kilo-meters, compared to 2300 kilometers for

Pluto—but with substantial error bars

Such errors are far smaller with a direct

view from orbit, Brown says The Hubble

Space Telescope zeroed in on Xena in

Decem-ber 2005 Brown showed the newly analyzed

image to about 1000 people at a public lecture

here at Foothill College The blob of light,

spanning several pixels on Hubble’s detector,

had enough resolution for Brown’s team to

determine that Xena is barely bigger than

Pluto Brown said he would reveal the

calcu-lated size at a NASA press briefing For now,

he said, “I’m going to stick with the word

‘smidge.’ It’s a really good word.”

But the size was evident from a statisticshown by Brown: Xena reflects a remarkable92% of optical light, like the f inest freshsnow “I had expected it to be darker and con-siderably larger,” Brown said This measure,called albedo, is derived from the object’sapparent brightness, distance, and diameter

According to a chart on Brown’s Web site, thatdiameter is roughly 1% larger than Pluto’s—

down from the team’s previous guesses of25% larger (on the Web site) to 50% larger (atNASA’s July announcement)

Icy bodies darken with age, so geysers

must recoat Xena’s surfacewith fresh frost, Brown said.Planetar y scientist DavidStevenson of Caltech notesthat Satur n’s active moonEnceladus is the only otherobject in the solar system thatglistens as radiantly But Ence-ladus flexes during its eccen-tric orbit around Saturn, gen-erating enough heat to expelicy compounds from themoon’s interior There’s noobvious way to spark suchaction on Xena—even with itssmall moon “Frankly, volcan-ism in the Kuiper belt is hard,”Stevenson says “Maybe wedon’t understand the dynamics

of cr ystallization and thephysics of ice surfaces.”

Nor will Xena help themessy debate over planetnomenclature Late last year, aworking group of the Inter-national Astronomical Union(IAU) failed to agree on any ofthree proposed “planet” def initions andpassed the buck to IAU’s executive commit-tee Astronomers are finding so many planet-like objects—both in our solar system andaround other stars—that the prudent coursemay be to wait instead of forcing a hasty con-sensus, says committee member Rober tWilliams of the Space Telescope ScienceInstitute in Baltimore, Maryland

Although people are loath to demote Plutofrom planethood, they may not want dozens ofPluto-size “planets” either, says Foothillastronomer Andrew Fraknoi “It’s almost cos-mic justice” that Xena and Pluto are a near-match, he says “Welcome to the borderland

New Hubble Image Cuts the “10th Planet” Down to Size

PLANETARY SCIENCE

Pointing the way 602

Pluto plus Distant “Xena”—shown in a ground-based image with itssmall moon—is barely bigger than Pluto, a new Hubble photo reveals

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Iranians Seeking Uranium

Negotiations over Iran’s nuclear program mayfounder on one key issue, Vienna-based

diplomats tell Science: whether Iranian

researchers will be permitted to work side byside with Russians on uranium enrichment

With Iran’s referral to the U.N Security

Council looming as Science went to press,

negotiators are pushing Iran to relinquish itsright to enrich uranium Under a Russian pro-posal, Russian centrifuges would boost thepercentage of fissile uranium in Iranian hexa-fluoride gas It’s hoped that would deter Iranfrom using its own centrifuges to produce evenhigher percentages of fissile fuel for bombs

The plan, sources say, restricts Iranian tists’ presence at the facility to thwart leakage

scien-of knowledge that might accelerate Iran’salleged weapons program

Iran has vacillated on the Russian proposal,and negotiations are expected to resume nextweek Iran “will insist on learning more aboutenrichment technologies if the deal goesthrough,” predicts Jack Boureston of nonprolif-eration research group FirstWatch International

–RICHARD STONE

Fish Science Center Cast Off

In a controversial move, the Bonneville PowerAdministration (BPA)—the U.S federal agencythat oversees Pacific Northwest hydropower—has appointed new groups to count salmonreturning to upstream spawning grounds Lastweek, BPA announced that it will cut ties inMarch to the Fish Passage Center (FPC), an11-person, $1.3 million operation that haslong provided data to biologists who determinefishing seasons and salmon-recovery plans

BPA will give fish-counting duties to thePacific States Marine Fisheries Commission,with routine analysis to be done by PacificNorthwest National Laboratory But RebeccaMiles of the Nez Perce Tribe, which has rights

to the fish, says that now is the wrong time forchanges, as comprehensive salmon-recoveryplans are under negotiation The move blocksaccess to “the best scientific data,” she says.But the replacements say they’re qualified,and BPA’s Greg Delwiche says separating thedata gathering from the analysis willstrengthen the underlying science

A federal judge cited FPC data last Julywhen he ruled that additional water needed to

be released from Columbia River dams, amove that cost BPA $79 million and triggeredthe ire of Senator Larry Craig (R–ID) Heinserted a provision into a spending bill forc-ing BPA to jettison FPC

–ROBERT F SERVICE

People change clothes depending on the

tem-perature outside Tomato hornworms change

color These caterpillars emerge green when

it’s above 28°C and black when it’s cooler

Now two insect physiologists report on page

650 that they have teased out a possible genetic

basis of this color change by breeding a mutant

strain of a related species, the tobacco

horn-worm, until it too undergoes a similar switch

The study demonstrates how species can

mask effects of genetic mutations until an

envi-ronmental trigger reveals them, an adaptive

mechanism that may help organisms survive

changing conditions The work “is a tour de

force of experimental evolutionary biology,”

says Mary Jane West-Eberhard, an evolutionary

biologist at the University of Costa Rica “It

[begins] to answer a question of fundamental

importance: How does a novel, environmentally

sensitive trait originate?”

Organisms that live in variable environments

often evolve traits—called polyphenisms—that

change according to particular conditions

Aphids become winged or wingless, for

exam-ple, depending on food availability The tomato

hornworm’s color change serves a similar

adap-tive purpose In the cooler northern United

States, the caterpillars that emerge in the autumn

are black to absorb more sunlight, but in thesouth, where camouflage is more important thanheat conservation, they’re green In contrast,tobacco hornworms are typically green, no mat-ter the temperature

The genetic underpinnings of polyphenismshave long been a puzzle, notes Douglas Emlen,

an evolutionary biologist at the University ofMontana, Missoula To examine how thetomato hornworm’s color-shifting may havearisen, Yuichiro Suzuki, a graduate studentworking with Frederik Nijhout at Duke Uni-versity in Durham, North Carolina, turned to atobacco hornworm mutant that is black ratherthan the normal green Its mutation reducessecretion of juvenile hormone, which regu-lates skin coloring This mutant strain, how-ever, generates cater pillars with varyingdegrees of green if it is heat-shocked—brieflyexposed to a very high temperature—at anearly stage of development

Suzuki used this heat-shock method toselect for two spinoff strains In one case, hemated only tobacco hornworm caterpillarsthat remained dark despite the heat shock,weeding out greenish ones each generation

By the seventh generation, this line, even afterbeing heat-shocked, produced only black lar-vae At the same time, Suzuki bred the cater-pillars that developed the greenest skin whenheat-shocked Over time, this selection haddramatic results, creating a strain whose cater-pillar form always emerges green instead ofblack if grown above a specific threshold tem-perature, 28.5°C

The experiments indicate that low juvenilehormone levels in the original black mutanthad enabled already-existing variants involved

in pigment production to exert their effects,depending on the temperature Nor maltobacco hornworms have very high amounts

of juvenile hormone, but Suzuki and Nijhoutshowed that the heat-insensitive version of themutant strain had very little and the newly cre-ated polyphenic strain had levels in between

In this latter strain, higher temperaturesresulted in more juvenile hormone and, conse-quently, greener skin Suzuki and Nijhout pro-pose that there may be other cases in whichevolution has exploited developmental hor-mones to create polyphenic traits

Evolutionary biologist Mark Siegal of NewYork University cautions that what happens inthe lab isn’t necessarily what happens in real life

But he applauds the study “[This] laboratorydemonstration is an important first step that willguide the crucial, and difficult, effort to under-stand actual evolutionary histories,” he says

–ELIZABETH PENNISI

Hidden Genetic Variation Yields

Caterpillar of a Different Color

EVOLUTION

Fashion statement Tobacco hornworms can evolve

a finely tuned sensitivity to heat that causes them to

emerge green instead of black

3 FEBRUARY 2006 VOL 311 SCIENCE www.sciencemag.org592

NEWS OF THE WEEK

STOCKHOLM—Public health efforts in the

developing world are missing out on a bargain,

say a group of researchers and health policy

leaders At a meeting here*and in a recent

paper, they argue that

the ramped-up efforts

against the Big Three—

HIV/AIDS,

tuberculo-sis, and malaria—will

yield far bigger

divi-dends if they are

cou-pled with an attack on

so-called neglected

diseases such as

hook-worm,

schistosomia-sis, and leishmaniasis

These infections make

their victims more

sus-ceptible to the Big

Three, the researchers

contend

Up to seven

neg-lected tropical diseases

could be tackled for just

40 cents per person per year, they say “It’s the

best buy in public health at the moment,” says

Alan Fenwick, a schistosomiasis researcher at

Imperial College London

Unlike HIV and malaria, phatic filariasis and onchocerciasis

lym-do not trip off the tongues of worldleaders Nor do such neglected dis-eases directly kill as many people as the BigThree Instead, they take their toll more insidi-ously, through stunted growth, anemia, andblindness, contributing to widespread develop-mental and learning delays These infections,both bacterial and parasitic, “are the world’sleading cause of growth def icits and theworld’s leading education problem,” says Peter

Hotez, a parasitologist at George WashingtonUniversity in Washington, D.C

But neglected tropical diseases are able to a concer ted campaign Effectivedrugs—inexpensive or donated by drug com-

vulner-panies—are available againstmany of them And in a paperpublished 30 January in the

Public Library of Science icine, Hotez, Fenwick, and

Med-their colleagues argue thattreating the 500 million peo-ple afflicted would cost just

$ 2 0 0 million a pared to $500 million pledgedthis year for antimalaria efforts

year—com-At the same time, the authorsargue, treating these seven dis-eases—the helminth infectionsascariasis, trichuriasis, hook-worm, lymphatic f ilariasis,onchocerciasis, and schistosomi-asis, and the bacterial infectiontrachoma—might benef it theongoing fight against the BigThree They point to a growingbody of evidence that suggests that populationsinfected with multiple parasites are more suscep-tible to other diseases—including the big killers.The payoffs for malaria control might beespecially worthwhile Intestinal parasites are

a leading cause of anemia—exacerbating one

of the main complications of severe malaria.Hotez points to a study in Senegal that foundthat deworming medicines signif icantlyreduced malaria cases

There is also preliminary evidence that HIVpatients infected with multiple parasites

Tackling Neglected Diseases Could

Offer More Bang for the Buck

INFECTIOUS DISEASES

Climate Change Demands Action, Says U.K Report

CAMBRIDGE, U.K.—As climate change climbs

up the political agenda, researchers have

pooled much of the most recent research into

what many believe is a compelling case for the

immediacy of global warming

This week’s report,*based on a meeting

convened last year at the request of U.K Prime

Minister Tony Blair, warns of catastrophic

consequences if steps are not taken now It

says a range of measures, from emissions

trad-ing to nuclear power, are needed to both

mini-mize future impacts and cope with those that

cannot be avoided “It is clear from the work

presented that the risks of climate change may

well be greater than we thought,” says Blair in

a foreword to the report “The U.K

govern-ment is taking this issue very seriously,” says

glaciologist David Vaughan of the BritishAntarctic Survey, “and it’s nice to see the gov-ernment consulting scientific opinion.”

During 2005, Blair was both chair of theG8 leaders of industrial powers and president

of the European Union and pledged to use histwin roles to combat global poverty and cli-mate change To advance the climate initia-tive, 200 researchers from across the globemet at the Hadley Centre for Climate Predic-tion and Research in Exeter last February Themeeting came 4 years after the last assessmentreport from the Intergovernmental Panel onClimate Change (IPCC)—the benchmark forglobal warming—and the scientists chewedover new results “It was a good time to takestock,” says steering committee chair DennisTirpak, head of the climate change unit at theOrganisation for Economic Co-operation andDevelopment in Paris

According to the meeting report,

“com-pared to the [IPCC’s 2001 assessment], there

is greater clarity and reduced uncertaintyabout the impacts of climate change.” Thereport contains models showing how theacidity of the oceans will increase as a result

of more carbon dioxide in the atmosphere Italso forecasts a 1000-year rise in sea levels as

a result of thermal expansion of the oceansand melting of the Greenland and Antarcticice sheets, even if greenhouse gas emissionsare stabilized “Once peripheral melting isunder way around Greenland,” Vaughan says,

“the ice sheet may enter a state where it can’tsustain itself.”

Tirpak says politicians need to realize thattime is running out and that the next genera-tion may live on a planet that has no icecaps inthe summer months “It will be a profoundlydifferent world, and we cannot imagine whatthat will mean,” he says “Do you want to risk

GLOBAL WARMING

Double benefit Treating the ascariasis worms that had

infected this girl (inset) may leave her less vulnerable to

other diseases

* U.N Millennium Project: A Malaria and Neglected

Trop-ical Diseases Quick-Impact Initiative, 30–31 January,

have higher viral loads and lower immune cell

counts than their counterparts who are

worm-free And several studies have shown that worm

infections can lessen the effectiveness of

vac-cines against other diseases “Unless we do

something about polyparasitism, we are not

going to have a big impact on the Big Three,”

Hotez says

On a practical level, the infrastructure for

distributing deworming drugs could also be

used to deliver antimalarial bed nets The

researchers hope to put their ideas into practice

soon At this week’s meeting, researchers and

public health leaders from eight African tries met to devise a “quick impact initiative”

coun-that would create national programs to tacklemalaria and the neglected diseases together

Getting drugs where they are most needed isthe greatest challenge, says William Lin ofJohnson & Johnson Lin is in charge of his com-pany’s effort to donate 50 million doses ofmebendazole, used to treat hookworm and otherhelminths “I’ve asked them to ramp up produc-tion,” he says “I don’t want to be left at the end

of the year with stores in the warehouse—and

Chinese HIV Offensive

BEIJING—Although China has fewer peoplewith HIV than previously estimated, the healthministry is about to expand efforts to curbnew infections

Last week, the ministry and two U.N ies announced that China in 2005 hadapproximately 650,000 HIV carriers, includ-ing 75,000 AIDS patients That’s 190,000fewer than in 2004, a decline largely attrib-uted to better data collection But the number

bod-of new infections is increasing, with 70,000having contracted the virus last year The min-istry now plans to expand condom distributionand methadone and clean needle provision forheroin addicts One high-risk group that willget extra help is China’s 120 million migrantworkers who travel from villages to cities, saysministry official Yao Deming –GONG YIDONG

Biotech Knockoffs Hit Europe

LONDON—A synthetic human growth mone called Omnitrope—a generic version of

hor-an out-of-patent drug by New York–based Pfizercalled Genotropin—may soon be available inEuropean pharmacies It’s expected to be thefirst so-called biosimilar drug to be marketedhere or in North America and could lead to aflood of less costly biotech products Pfizer hadargued that regulators should be wary ofapproving any such biosimilar drugs becausequality and safety depend on unique proper-ties and exquisite control of batch processing.But a scientific panel of the European Medi-cines Agency gave the green light last week,and the European Commission will likely follow in 90 days

The European vote raises the stakes at theU.S Food and Drug Administration, which hasbeen sitting on a similar appeal from Sandoz

–ELIOT MARSHALL

Clouds of Silence?

The chair of the House Science Committee hascriticized NASA for what he sees as its heavy-handed treatment of James Hansen, director ofNASA’s Goddard Institute for Space Studies inNew York City, a longtime voice on the dangers

of global warming “Good science cannot longpersist in an atmosphere of intimidation,” saysRepresentative Sherwood Boehlert (R–NY) in aletter to NASA Administrator Michael Griffinsent this week after news reports that theagency is trying to muzzle Hansen “NASA isclearly doing something wrong,” wroteBoehlert NASA officials insist that all agencyemployees are subject to the same rules, andthat Hansen is not being singled out

–ANDREW LAWLER

NIH Lends a Hand to Postdocs Seeking to

Become Independent Researchers

Concerned about the graying of the

investiga-tors it funds, the National Institutes of Health

(NIH) last week unveiled a new “bridge” grant

to help postdocs become independent

researchers Individuals could receive nearly

$1 million over 5 years to cover research and

training expenses The f irst awards will be

made next fall

Even in tight budget times, “nothing is more

important than supporting the new investigators

early,” said NIH Director Elias Zerhouni of the

$390 million program The

funding will come from taking a

“sliver” of each institute’s

over-all budget, Zerhouni says The

chair of a 2005 National

Acade-mies panel that recommended

the award’s creation is delighted

with the result “This is exactly

the sort of thing we were hoping

for,” says Thomas Cech,

presi-dent of the Howard Hughes

Medical Institute in Chevy

Chase, Maryland

The average age of a Ph.D

investigator winning his or her

first research grant, called an

R01, has risen from 37 to 42 in the past 25

years Nearly a decade ago, NIH abandoned a

smaller research award for young investigators

because it didn’t seem to help scientists get

R01s Now NIH is trying again

The Pathway to Independence award

com-bines traditional training and research grants

(Science, 9 December 2005, p 1601) The first

1 or 2 years cover the completion of a postdoc,

at $90,000 per year (including 8% for

over-head costs) Grantees who win a position as a

tenure-track assistant professor can then apply

for up to $250,000 a year for 3 more years for

research NIH says non–tenure track research

faculty members are also eligible The hope is

that these investigators will then be in a good

position to win R01s

The research portion of the grant will coverfull overhead costs, which can be as high as50% That feature should give universities astrong incentive to create positions for theseinvestigators, Zerhouni says “This is going tomake it a lot easier for postdocs to get a facultyposition because they’re bringing so muchmoney with them,” adds Alyson Reed, execu-tive director of the National PostdoctoralAssociation, which had also recommendedthe award’s creation

NIH hopes to award 150 to 200 fellowships

a year in the next 6 years to postdocs sored by their institutions “That’s enough toreally make a difference,” says Cech Indeed,NIH hopes that the new award will help boostthe share of R01s going to new investigatorsfrom 20% to 25% (see graph) Cech says it’salso important that non-U.S citizens are eligi-ble and that the grants can be transferred toother institutions

spon-NIH is still weighing another dation from the academies panel for a new-investigators R01 program with grants based

recommen-on experience rather than data NIH’s envirrecommen-on-mental health institute has begun a pilot proj-ect to test the idea

environ-–JOCELYN KAISER

BIOMEDICAL RESEARCH POLICY

A Sliding Share for New Investigators

3 FEBRUARY 2006 VOL 311 SCIENCE www.sciencemag.org594

NEWS OF THE WEEK

A halo in an image of a distant

galaxy rules out some

concep-tions of the frothy “quantum

foam” thought to make up

space and time at the smallest

scales, a team of physicists

claims If true, the observation

clamps the first experimental

limit on quantum gravity, the

highly theoretical f ield that

strives to mar r y quantum

mechanics and Einstein’s

gen-eral theory of relativity

Ironically, 3 years ago the

team shot down a similar claim

that quantum foam would

oblit-erate the optical artifact But the

new analysis takes into account a

physical effect the previous work

missed, and others say it appears sound “I

looked at it as carefully as I could, and I could not

find any obvious mistake,” says Eric Perlman, an

observational astrophysicist at the University of

Maryland, Baltimore County

The halo appears around a quasar—the

fiery heart of a galaxy—in an infrared image

the Hubble Space Telescope snapped in 1998

The “Airy ring” arises because light waves

dis-tort slightly as they bounce off the edges of a

telescope’s mirror, in ways that create rings

around any pointlike object

But the effect occurs only if the waves remain

neat and orderly as they travel the 4 billion

light-years from the quasar Quantum foam would

fuzz them out, say theoretical physicist Yee Jack

Ng and colleagues at the University of North

Carolina, Chapel Hill So the halo rules out the

most chaotic models of the foam, they argue in a

paper to be published in Physical Review Letters.

That’s a big claim, as most theorists agree that the

foam is an unavoidable consequence of melding

quantum uncertainty with Einstein’s notion that

spacetime is stretchy and dynamic

In 2003, astrophysicists Richard Lieu and

Lloyd Hillman of the University of Alabama,

Huntsville, also concluded that the halo

torpe-doed the notion of quantum foam Within the

minuscule foam, concepts of distance and

dura-tion lose precise meaning As a result, Lieu and

Hillman argued in the Astrophysical Journal,

quantum foam should create an uncertainty in

how far the light from the quasar had to travel to

reach Hubble That uncertainty should blur the

wave fronts and eliminate the ring

But Lieu and Hillman assumed that the

uncertainty would grow in proportion to the

dis-tance to the quasar Ng and colleagues pointed

out in the Astrophysical Journal that if the foam

varied randomly, then the uncertainty would

increase in proportion to the square root of the

distance, making the effect imperceptibly small

Now, Ng and colleagues have considereduncertainties not only in the distance the lighttravels but also in its direction, which changes

as the light scatters off the “bubbles” in thefoam The scattering greatly increases theblurring effect, Ng says So the presence of thering rules out a randomly varying quantumfoam after all Less random versions could stillexist, however, as fluctuations in the foammight conspire to reduce the blurring

“In my view, this is a compelling ment,” says Demos Kazanas, a theoreticalastrophysicist at NASA’s Goddard Space FlightCenter in Greenbelt, Maryland GiovanniAmelino-Camelia, a quantum gravity theorist

argu-at the University of Rome “La Sapienza” inItaly, says, “I’m starting to believe that I shouldinvest in this” line of inquiry

As for Hillman, who died in 2005, andLieu, “their suggestion was a good one, even

if their argument was flawed,” Ng says.Researchers can test the idea by looking forhalos in images of other quasars, and larger tel-escopes should be able to detect smaller effects

of the foam and probe other theoretical models

–ADRIAN CHO

Ring Around a Quasar May Deflate Quantum Foam After All

THEORETICAL PHYSICS

Bandwagon Builds for Energy Research

Influential Washington policymakers havedecided that bolstering U.S technical know-how and tackling energy challenges should gohand in hand Their solutions are featured in aseries of recent legislative proposals, includ-ing the bipartisan Protecting America’s Com-petitive Edge (PACE) package, introduced inthe Senate last week The more-than-$70-billion package, like several other bills intro-duced in December, includes more money for

researchers and science educators funded bythe Department of Energy (DOE)

The rapid economic development in Indiaand China, a stagnant U.S manufacturing base,and the poor performance by U.S students onstandardized tests in math and science havespurred a surfeit of recent legislative plans totackle domestic competitiveness Meanwhile,the rising demand for oil, tensions in the Mid-dle East, and concerns about carbon emissions

are pushing lawmakers to ate the development of new energytechnologies Both challengeswere mentioned in a NationalAcademies report released last fall

acceler-(Science, 21 October 2005, p 423).

Previewing his State of the Unionaddress earlier this week, Presi-dent George W Bush told Bob

Schieffer of CBS News that an

effort “to promote and activelyadvance new technologies” couldmake the U.S “independent fromforeign sources of oil.”

That rhetoric signals thedemise of an era in which “con-gressional support of science wasbuilt on the pillars of defense andhealth,” says former Massachu-setts Institute of Technology presi-dent Charles Vest, who predicts

t h a t e n e rg y - e nv i r o n m e n t ,

U.S INNOVATION

Bubble burster Irislike “Airy ring” around quasar PKS 1413+135

(black dot, center) may nix some versions of quantum foam.

Sunny and hot forecast New funding proposals would boostenergy research for areas such as photovoltaics and inherentlysafe nuclear power (shown here, a decommissioned plant in

competitiveness-innovation, and health will be

the new drivers of research funding

Some would like to recreate the excitement

of the Apollo space program in the 1960s by

picking a challenging technological target that

could weld research with national priorities

Norman Augustine, former chair and CEO of

Lockheed Martin, chaired the academies’

panel, which considered a so-called National

Energy Initiative Likewise, lawmakers

craft-ing the PACE act at one point toyed with

target-ing development in specific energy areas such

as nuclear energy But the “decision was to let

that happen [naturally],” says PACE co-sponsor

Senator Pete Domenici (R–NM)

That approach is fine with Augustine A focus

on energy “happens to coincide with physics,

engineering, and math,” he says Both PACE and

the academies report also call for a 10%-a-year

boost in federal funding for basic research

PACE would give DOE an increased role in

encouraging college students to major in science

and engineering and improving training for

sci-ence and math teachers at all levels through new

scholarships It also calls on DOE’s national

lab-oratories to support summer internship

pro-grams for gifted students Insiders say Raymond

Orbach, head of DOE’s Office of Science and a

former university president, helped persuade

lawmakers to give DOE a larger national role in

science education

One proposal in several of the bills is a

new DOE research agency modeled on the

Pentagon’s Defense Advanced Research

Pro-jects Agency Aimed at encouraging risky,

high-payoff energy science, the new agency,

dubbed ARPA-E, would recruit academic

and industrial leaders for short periods to

craft and manage innovative research

initia-tives Nobelist Steve Chu, director of DOE’s

Lawrence Berkeley National Laboratory in

California, says that such an agency would

help “bridge the funding gap” that now exists

between well-established yet risky science,

such as fusion research, and basic work with

hard-to-anticipate benef its, such as that in

particle physics ARPA-E is also part of a

package of bills introduced in December by

Representative Bart Gordon (D–TN),

rank-ing Democrat on the House Science

Commit-tee, and a recent proposal by Senate

Democ-rats Although not mentioned by name, the

approach is also endorsed in a December

innovation bill introduced by Senators John

Ensign (R–NV) and Joe Lieberman (D–CT)

These legislative proposals may reflect a

convergence of thinking in Congress But

sup-porters will also need to convince spending

panels Advocates don’t see that as an

insur-mountable obstacle PACE co-sponsor Senator

Lamar Alexander (R–TN), for example, calls

PACE’s multibillion-dollar cost “a small price

for a high standard of living.”

–ELI KINTISCH

NEWS OF THE WEEK

TOKYO—A University of Tokyo chemist hasbeen stripped of his teaching duties and hisgraduate students following an investigationunprecedented in Japanese academia Lastweek, university officials announced that agroup led by Kazunari Taira has been unable toreproduce findings from four key papers Tairamaintains he has done nothing wrong asidefrom failing to ensure that experimental datawere properly recorded The headline-grabbing case is likely to spur other institu-

tions to establish procedures for handling conduct allegations

mis-An investigation began last spring after theRNA Society of Japan wrote to the universityraising questions about 11 papers that appeared

between 1998 and 2004 in Nature, Nature

Biotechnology, the Proceedings of the National Academy of Sciences, and other journals The

society acted on reports from scientists in Japanand from overseas saying they could not repli-cate the group’s results, sources say HiroakiKawasaki, a research associate in Taira’s lab,was first author on 10 of the 11 papers Tairawas corresponding author of nine papers; heand Kawasaki were co-authors of the other two

A panel led by Yoichiro Matsumoto, amechanical engineer in the Graduate School

of Engineering, was formed to probe theRNA Society’s concerns In an interim reportreleased last September, the committeeannounced that a number of specialists con-tacted by the panel claimed they were unable

to reproduce Taira’s results The committee

then selected four papers for a closer look andfound that the group could not produce rawdata or notebooks to support the f indings

(Science, 23 September 2005, p 1973).

Taira insisted that he could repeat the ments, so the committee asked him to do so.Kawasaki claimed to have replicated the find-ings in one of the papers, but the panel found that

experi-he had used materials different from thosedescribed in the original paper Taira says moretime is needed to work on the other experiments.However, at a 27 January media briefing, Mat-sumoto said bluntly, “At this time, there is noevidence the experiments can be repeated.”

Junichi Hamada, a university vice dent, said at the press briefing that both Tairaand Kawasaki will now face a disciplinarycommittee and could be dismissed In themeantime, the Graduate School of Engineer-ing has relieved Taira of teaching duties andtransferred his 25 graduate students to otherteams His own research has ground to a halt,and he says he will have to restart his career

presi-“from scratch.”

“If I was just making up data, I wouldn’thave had to work the 100 hours a week I wasworking,” says Taira, whose recent studiesinvolve RNA But he concedes that his group

is having trouble reproducing some results

The investigation was the first ever by theUniversity of Tokyo, widely considered to beJapan’s most prestigious The university ismulling the establishment of a permanentcommittee or office to address research mis-conduct, says panel chair Matsumoto

Observers say they are pleased with theoutcome “The University of Tokyo should behighly praised for its handling of this investi-gation,” says Norihiro Okada, a molecularbiologist at the Tokyo Institute of Technologyand one of the members of the RNA Societywho urged an inquiry

Okada and others believe that the case hasfocused attention on the need for more policing

of misconduct RIKEN, the nation’s premiercollection of basic research institutes, is ahead

of the game Its auditing and complianceoffice, created last April, now has the authority

to investigate any hints of misconduct EachRIKEN group must now make experimentalrecords available for inspection for 5 years afterpublication, and the contributions and respon-sibilities of every author must be made clear.Office director Fumikazu Kabe says the policymight have to be modified for adoption by uni-versities, “but it probably is something theycould use as an example.”

–DENNIS NORMILE

Panel Discredits Findings of Tokyo University Team

SCIENTIFIC CONDUCT

Case closed? A University of Tokyo panel has

|concluded that certain findings from chemist Kazunari Taira’s team could not be substantiated

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3 FEBRUARY 2006 VOL 311 SCIENCE www.sciencemag.org596

ANY DRIVER WILL AGREE THAT A YELLOW

light at a traffic intersection presents a

conun-drum Should one hit the brakes to stop or keep

going—speeding, if necessary, to beat the red

light? A number of factors could influence the

choice, including the degree of recklessness of

the driver, the urgency of the trip, and, not

least, whether a police car is in sight But the

key element in the decision is the person’s

estimate of how much time it will take for the

signal to turn red

Time is integral to myriad other questions

in everyday life: how long to grill one side of a

burger before flipping it, how long to let a

phone ring before hanging up, or how long to

wait during a pause in conversation before

treating it as a speaking cue In both people

and animals, the brain’s ability to keep track of

intervals is fundamental to innumerable

behaviors Some, such as walking and singing,

rely on timing on the order of tens to hundreds

of milliseconds Others, such as foraging and

making decisions, including the yellow-light

problem, involve judgment of intervals on the

scale of seconds to minutes and hours As

Warren Meck, a cognitive neuroscientist at

Duke University in Durham, North Carolina,

puts it: “Timing is everything.”

For decades, researchers have sought to

uncover the neural basis of time perception

They’ve been motivated in part by success at

understanding the circadian clock: the

biologi-cal timer that regulates the day-night cycle In

mammals, this 24-hour timepiece has a specific

home: the brain’s hypothalamus Not

surpris-ingly, scientists have hoped to discover a ized structure somewhere in the brain dedicated

local-to tracking shorter time intervals But now, ing researchers are all but abandoning thesearch for such an interval timer in any singleregion of the brain Instead, they are increas-ingly convinced that the brain judges intervals

tim-on short time scales—millisectim-onds to minutesand hours—with the help of a distributed net-work of neurons This shift is being driven by aslew of f indings from electrophysiologicalstudies on animals, behavioral experimentsinvolving patients with brain lesions, andneuroimaging studies of healthy people

In addition to identifying the differentbrain regions that play a role in timing, theseexperiments are prompting scientists toreexamine the classic view of how neuronskeep track of time And even though that hasnot yet led to a mechanistic account that sat-isfies everybody, researchers say the effort ishelping to take timing research beyond thespeculative realm of psychology into the

f irmer ter ritory of neuroscience “We’re

f inally getting some neural reality into thepicture,” says Russell Church, a psychologist

at Brown University, who has studied timingfor more than 30 years

A distributed timekeeper

Inspired by the hypothalamic circadian clock,researchers began looking for a short-time-scaleclock in the brain in the 1970s Some focused

on the hippocampus, assuming that time ception was related to memory Others searchedthe cerebellum By the mid-1990s, many wereconvinced that the clock was located in thebasal ganglia

per-Yet in recent years, neuroscientists havelinked multiple areas throughout the cortex totime perception Some evidence has comefrom neuronal recordings in animal brains

In 2003, for example, Michael Shadlen, a

neuroscientist at the University ofWashington, Seattle, and hisgraduate student Matthew Leonrepor ted training monkeys tomake eye movements based onduration judgments in the range of0.3 to 1 second The two foundthat neurons in the animals’ posterior parietalcortex increased their f iring rate based onhow much time had elapsed The results sug-gested that these neurons track the flow oftime relative to a remembered duration Otherteams of researchers, including one led byYoshio Sakurai of Kyoto University in Japan,and a group led by Carlos Brody at ColdSpring Harbor Laboratory in New York, haveobserved similar patterns of neuronal activity

in the prefrontal cortex of monkeys ing timing tasks

perform-Evidence for the involvement of differentcortical areas in timing has also come from

A Timely Debate

About the Brain

Neuroscientists have recently shown that multiple

brain regions are used to judge short intervals,

but fierce disagreement continues over how neurons

in those regions measure time

“We’re finally getting some neural reality into the picture.”

—Russell Church, Brown University

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studies of patients with brain lesions In 2002,

a team led by Giacomo Koch, then at Italy’s

University of Rome, reported on a patient with

a prefrontal cortical lesion who underestimated

durations of a few seconds—time to him

seemed to pass more quickly than it actually

did The same year, a g roup led by Marc

Wittmann of Ludwig Maximilians University

in Munich, Germany, described patients with

lesions in other cortical areas who also

under-estimated durations longer than 3.5 seconds

Then in 2003, Koch and his colleagues showed

that they could induce healthy subjects to

underestimate multisecond intervals by

sup-pressing their prefrontal cor tices with a

focused magnetic field

Some of the clearest evidence for a

dis-tributed picture of timing has come from

neuroimaging studies In one such study,

researchers in France asked 12 subjects to

compare the color and duration of two circles

presented one after the other on a computer

screen (Science, 5 March 2004, p 1506) Each

circle was colored one of three shades of

pur-ple and stayed on for one of three durations:

0.5, 1, or 1.6 seconds In some trials, the

sub-jects had to indicate if the second circle was

bluer or redder than the first; in others they

judged if the second circle appeared for a

longer or shorter duration

Functional magnetic resonance imaging

scans of the volunteers showed activation of an

extensive network of brain areas during the

time estimation task; in contrast, only the

V4 area of the visual cortex lit up during the

color-judgment task Also, the various areas

that lit up during the timing task—including

the prefrontal and parietal cortices and the

basal ganglia—showed increases in activity as

the subjects paid more attention to time

“Although visual features such as color or

motion or form can be linked to

single-feature-specific processing areas, timing information

appears to be coded in a distributed network of

brain regions,” says Jennifer Coull, a cognitive

neuroscientist at the Centre National de la

Recherche Scientifique in Marseille, France,

and lead author of the study “Maybe we have

to integrate several sources of information in

order to estimate time because it is so much

less tangible to our senses than visual features.”

In the August issue of Human Brain Mapping,

a different French group led by Viviane Pouthas of

the Salpêtrière Hospital in Paris reported

activa-tion in a similar set of brain regions when subjects

timed intervals that were about 0.5 and 1.5

sec-onds long The researchers also observed that a

subset of these regions—including certain areas

of the cortex and the striatum—showed higher

activity when subjects estimated the longer

dura-tion Pouthas says this subset could be playing a

direct role in time estimation, distinct from other

components of the task such as recalling and

comparing intervals

How it works: The old and the new

Although most researchers are now vinced that timing involves multiple regions

con-of the brain, they disagree on how neuronsactually keep track of time Until recently, theprevailing theory had been that some neuronsrelease pulses of one or more neurotrans-mitters at periodic intervals while other neu-rons accumulate them, in the same way that acup placed under a steadily dripping faucetaccumulates drops of water As the receiving

neurons register more and more signals, thesense of time that has passed grows More-over, quantities of accumulated pulses corre-sponding to specific durations are recorded inlong-term memory, allowing an individual tocompare newly encountered time intervals tothose previously experienced

This account of time perception—known

as the pacemaker-accumulator model—hasheld sway since it was proposed in the 1970s

by the late John Gibbon, a psychologist atColumbia University Researchers have foundthe model to be a handy framework forexplaining a fundamental feature of timing,seen in both animals and humans, called thescalar property—which is that the amount oferror in estimating time intervals increaseslinearly with the duration being timed Themodel has also provided psychologists with agood handle on a variety of other behavioralfindings related to timing

But now it is being challenged by some astoo simplistic—and perhaps even fundamen-tally flawed One challenger is Meck, a pro-tégé of Gibbon and once a strong proponent

of the pacemaker model His g roup hasrecently put forth a new idea that has garneredsupport from many in the field but strong crit-icism from others

Meck spent the 1980s and the early 1990sseeking to identify the neural pieces of thepacemaker-accumulator model Althoughthis system could in theory operate in a spe-cific brain region, it could also involve multi-ple regions, as might be expected by the morerecently embraced idea of a distributed neu-ral network Working with Chara Malapani, aclinical psychiatrist at the New York Psychi-atric Institute in New York City, and others,Meck proposed in the mid-1990s that thebrain’s stopwatch was located in the basalganglia, comprising dopamine-secreting

“pacemaker” neurons in the substantia nigraand “accumulator” neurons in the striatum.Some of the evidence for this hypothesiscame from studies of Parkinson’s diseasepatients, whose poor performance on timingtasks was found to be linked to the loss ofdopamine-producing neurons Researchersfound that medicating these patients withL-DOPA, a drug that increases dopaminelevels, improved their timing

Even though the dopamine work seemed toput flesh on the pacemaker theory, the modelran into trouble a few years later At the time,Meck was already somewhat skeptical aboutthe capacity of neurons to linearly sum up tem-poral pulses over the course of seconds to min-utes Then one of his doctoral students,Matthew Matell, marshaled evidence from theneurobiological literature that convinced Meckthat dopamine could not drive neurons in thestriatum to fire in the simplistic way proposed

by the pacemaker model

M e c k a n d M a t e l l h ave d eve l o p e d a nalternative model in which the striatum readsout intervals from a snapshot of activityacross a network of cortical neurons Thedifferent neural populations in the cortex—all connected to neurons in the striatum—have f iring rates that oscillate at differentfrequencies At any given point, the pattern

of activity across the cortical network—thesynchronous firing by a certain ensemble of

Spread out Multiple brain regions are activated in

a time-estimation task (top); a few of these regions (bottom) show increased activation while estimating

longer intervals

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