Schizophrenia may well be themost mysterious of all mental ill-nesses. Psychiatrists long blamed

bad parenting, but the evidence nowÞngers faulty genes: four separate pa-pers in the November 1995 issue of Na-

ture Genetics singled out a suspiciousDNA sequence on chromosome six.(Two reports in the same issue failedto conÞrm the link.)

Even so, the mystery is far fromsolved. Although the damage may bedone early on, schizophrenic symp-tomsÑwhich include paranoia, delu-sions, social withdrawal, auditory andvisual hallucinations, and disorganizedthoughtsÑoften do not surface untiladulthood. Patients bear none of the tell-tale tumors or lesions that lie behindsome similarly disruptive disorders.

Having found little wrong in the formof a schizophrenicÕs brain, many work-ers are turning their studies towardfunction. David A. Silbersweig and Emi-ly Stern of the New York HospitalÐCor-nell University Medical Center, working

with colleagues at Hammersmith Hos-pital in London, devised a clever meansfor exposing the brainÕs blood ßow inthe act of hallucinating. They examinedsix schizophrenic men, all of whomheard voices and were unresponsive orunexposed to treatment; one had visualhallucinations as well. The team placedeach subject in a positron emission to-mography, or PET, scanning machineand asked him to press a button withhis right thumb when he hallucinated.

In the November 9, 1995, issue of Na-

ture, the group reported that tissues atthe brainÕs surface needed for hearingwere active in all the patients. In theman who had visual hallucinations, ac-tivity was also observed in the corticalareas involved in coordinating sightsand sounds. All the men had increasedblood ßow in another set of structures,positioned deeper in the brain, includ-ing the hippocampus, parahippocam-pal gyrus, cingulate gyrus, thalamusand striatum. ÒAll these interconnectedregions are involved in integrating

thoughts and emotion,Ó Silbersweig says.SigniÞcantly, the hallucinators did notexperience higher blood ßows in anarea used to distinguish between inter-nal and external stimuli.

Carol Tamminga of the Maryland Psy-chiatric Research Center has also foundevidence that hallucinations stem fromprocesses deep within the brain. At theannual meeting of the Society for Neu-roscience in San Diego last November,she described PET scans she took of 24volunteersÑhalf of them schizophrenicand the other half healthyÑafter theyreceived ketamine, a drug that prompt-ed psychotic symptoms in both groups.ÒThe activity in the anterior cingulategyrus greatly increased in both schizo-phrenics and normals,Ó Tamminganotes. ÒBut the schizophrenics showeda far greater increase.Ó

Next, Tamminga analyzed the eÝectsof haloperidol, an antipsychotic drug.Haloperidol blocks receptors in thebrain that bind to dopamine, a neuro-transmitter suspected of playing a keyrole in schizophrenia. As expected, themedication lowered neuronal activityin the frontal and cingulate regions ofthe cortex but increased blood ßow in

22 SCIENTIFIC AMERICAN February 1996

The conservative tide that has gripped America deridesprograms intended to foster ethnic or racial under-

standing as a threat to core social values. Conservativepundit Rush Limbaugh rails that multiculturalism is the“tool of revenge of many who have failed to assimilateand fit into mainstream American life.” During comingdecades, public debate will most likely focus on what ex-actly constitutes “mainstream American life.” The Lim-baughian backlash represents a reaction to an inexorabledemographic trend. White European Americans face thethreat of losing their majority status in U.S. society.

By the year 2055 groups now classified as minorities,taken together, will probably outnumber whites of Euro-pean descent—a result of immigration and higher fertility.

The crossover point will happen even sooner—in the year2030—for school-age children, according to researchersfrom the University of Florida. By that year, moreover, Lati-nos will become more numerous than blacks (graphs).

Joe R. Feagin, a professor of sociology at the Universityof Florida, foresees that these groups may achieve new-found power by the strength of their votes. The weight ofnumbers could create a rainbow majority that wouldchange the face of American politics. Whites will still bethe largest single group, but Feagin believes that complexbrokering among ethnic and racial coalitions may or maynot leave whites on top. “Whites can still rule as a minorityif the subgroups in a rainbow majority are at loggerheadswith one another,” Feagin says.

Divisiveness training classes mayhave already begun as a replacementfor multicultural education. Feaginpoints to books such as Alien Nation,authored by Forbes senior editor Pe-ter Brimelow. Alien Nation beginswith the statement that current immi-gration policy may be Adolf Hitler’srevenge on America—a human tidalwave that may destroy the country.“These writings are not so differentthan white supremacist publicationsanalyzing the need to restore white,racial hegemony,” Feagin remarks. Ifvisions of an alien nation prevail, arainbow majority may be supplantedby the monochrome realities of aneoapartheid. —Gary Stix

The Rainbow Majority

Schizophrenia RevisitedNew studies focus on malfunctions in the brain

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YEAR YEARSOURCE: Projections compiled from U.S. Census Bureau data by University of Florida researchers (Joe R. Feagin, Hernán Vera and Barbara A. Zsembik).

SOURCE: Projections compiled from U.S. Census Bureau data by University of Florida researchers. The blue trend line is extended to 2055, when whites may constitute less than 50 percent of the population.

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several regions in the middle of thebrain. Tamminga also recorded abnor-mal activity taking place in the cingulategyrus when schizophrenics attemptedto discriminate between similar sounds.Although the schizophrenic patientsperformed as well as normal subjectsdid on these auditory tests, they usedmore of their brain in the process.ÒSchizophrenics activated all the cor-rect areas and just a couple more,Ó Tam-minga states, Òbut they didnÕt use themin a normal fashion.Ó

Neuropathology also indicates func-tional problems in some of the samecerebral circuits. The cingulate gyrus inschizophrenics typically contains fewerGABA, or inhibitory, neuronsÑcells thathelp to Þlter incoming stimuliÑnotesFrancine Benes of McLean Hospital inBelmont, Mass., and Harvard MedicalSchool. Benes has investigated whetherexcess dopamine might cause this de-crease. She counted the contacts be-tween dopamine-releasing Þbers in thebrain and other excitatory and inhibito-ry neurons in postmortem tissue sam-ples taken from 10 schizophrenic and15 unaÝected people. In all the speci-mens, the dopamine Þbers made morecontacts with inhibitory neurons, butthe pattern was most pronounced in thecingulate gyrus of the schizophrenics.

Like other researchers, Benes suspectsthat the inhibitory neurons in schizo-phrenics are impairedÑa situation thatwould only be made worse by a delugeof incoming dopamine. ÒMy model pos-tulates that the medications we use totreat schizophrenia block the dopa-mine receptors on the inhibitory neu-rons, thus freeing them up to performmore eÛciently,Ó Benes explains.

The greatest number of contacts be-tween inhibitory neurons and dopamineÞbers in schizophrenics appeared inlayer II of the cingulate cortexÑa layerthat is actively developing near the timeof a normal birth. This discovery helpsto corroborate the theory that obstetriccomplications may increase the likeli-hood of an infant acquiring schizophre-nia later in life, Benes adds.

ÒThe consensus is that schizophreniais neurodevelopmental and that it verylikely involves some abnormality in theway the structures that mediate infor-mation processing are connected,Ó saysNancy Andreasen of the University ofIowa. For now, this theory cannot oÝermuch help to the 1 percent of the popu-lation worldwide aÝected by schizo-phrenia. But serious investigations intothe disease have only just begun: ÒOncewe Þnd the mechanism,Ó Andreasenbelieves, Òwe will be able to Þnd bettertreatments and maybe even means ofprevention.Ó ÑKristin Leutwyler

SCIENTIFIC AMERICAN February 1996 23

When the French government resumed testing nuclear weapons lastSeptember below the South Pacific atolls of Mururoa and Fangataufa, it

provoked an international uproar of surprising intensity. Attempting to quellit, French officials reduced the number of planned tests from eight to six andportrayed most of them as a necessary preliminary step to the country’s par-ticipation in a worldwide ban on testing, which negotiators hope to imple-ment by the end of this year. To nuclear experts outside France, however, theofficial rationale for the tests makes little sense.

By all accounts, one of the tests was to make sure that the TN-75, a newwarhead for submarine-launched ballistic missiles, worked well. This testtook place on October 1 under Fangataufa. It is the other five tests (of whichthree had been carried out by mid-December) whose purposes are some-what murky. According to Daniel LeRoy, counselor for nuclear affairs at theFrench Embassy in Washington, D.C., all these tests are to generate a lastburst of data. The information, he says, is necessary to help the country’s nu-clear scientists adapt to a post–cold war world in which trials involving nu-clear weaponry are limited to so-called aboveground experiments that donot entail nuclear blasts.

Last fall French president Jacques Chirac said a couple of tests in the serieswould be used mainly to study “mixing,” a potentially problematic phe-nomenon during the detonation sequence that saps energy from the overallyield. But experts say it is hard to imagine French scientists, who have al-ready conducted more than 200 tests, significantly advancing their under-standing of the phenomenonin this short series.

In a recent statement to thepress, Jacques Bouchard, di-rector of the military divisionof the French Atomic EnergyCommission, said French nu-clear-weapons designs hadbecome so sophisticated thatofficials could not have confi-dence the weapons wouldwork in the absence of test-ing. Simpler designs thatcould be trusted to workwithout having been testedwere needed, he noted, add-ing that the validation of suchdesigns was “one objectiveof the final test campaign.”

“These tests are being con-ducted to increase Frenchconfidence in their nucleardeterrent under a CTB [com-prehensive test ban],” says Christopher E. Paine of the Natural Resources De-fense Council (NRDC), a Washington, D.C., legal and research organization.

Puzzlingly enough, however, in interviews in 1994 with U.S. nuclear ex-perts, both Bouchard and his predecessor, Roger Baléras, asserted that thecountry would need 10 to 20 more tests to produce the robust weapons suit-ed to deployment under a CTB. Suzanna van Moyland, a researcher at theVerification Technology Information Center, suspects that the French are test-ing a new warhead variant in this final series. “They’d have the data alreadyif it wasn’t a new variant,” she reasons. “It would be a laborious, expensiveand politically risky venture just to get the same results again.”

Whatever the true purpose of this series, it has already accomplished some-thing unexpected, if unintended, according to Robert S. Norris of the NRDC.As recently as last summer, French officials had been insisting that a test-banagreement allow tests with yields up to several hundred tons. But “in an ironicway, Chirac’s decision to resume testing, and the outcry against it, has forcedthe French to retract their insistence on these permissible yields and adopt atrue, zero-yield test ban,” Norris declares. “That’s the most important thing.And nobody could have predicted it would happen.” —Glenn Zorpette

Going Out with a Bang

TAHITIANS protested the French resumptionof nuclear testing on nearby Mururoa.

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Copyright 1996 Scientific American, Inc.