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What is consciousness? Study aims to settle debate

Research would also subject claims of “out of body” experiences to strict test

May 20, 2007
Special to World Science  

In sci­ence, plen­ty of prob­lems are hard. But per­haps just one is so grue­somely try­ing that sci­en­tists them­selves have termed it, well, “the hard prob­lem.” How does con­scious­ness arise—the liv­ing, aware ex­pe­ri­ence of be­ing?

Some the­o­ries hold that it comes from, or is even iden­ti­cal to, elec­tri­cal and chem­i­cal pro­cesses known to un­fold in the brain. Oth­ers say it arises else­where: in some even sub­tler, yet-un­dis­cov­ered brain pro­cesses, or per­haps a mind-stuff quite dis­tinct from the brain—some call it a soul.

Ces­sa­tion of brain ac­tiv­i­ty is rec­og­nized when a device known as an elec­tro­en­ce­pha­lo­gram, set up to re­cord the brain's elec­tr­ical activity, de­tects no activity be­yond the in­her­ent in­ter­nal noise of the ma­chine it­self. The read­out from the de­vice then ap­pears as flat line.


Few on ei­ther side claim to have fi­nal an­swers. But they of­ten ar­gue pas­sion­ately over who’s at least in the right play­ing field.

Now a group of re­search­ers has be­gun a study that they say might set­tle the is­sue. “We can ac­tu­ally test this, and put and end to all these de­bates,” said Sam Par­nia, a crit­i­cal care doc­tor at Weill Cor­nell Med­i­cal Cen­ter in New York. 

Par­nia has spent years stu­dying re­ports that some car­di­ac-ar­rest pa­tients keep hav­ing clear, dis­tinct thought pro­cesses af­ter they’re clin­ic­ally dead and de­tect­a­ble brain ac­ti­vity has ceased. Pa­tients com­monly re­count these men­tal ex­pe­ri­ences, which of­ten in­clude see­ing a light at the end of a tun­nel, af­ter be­ing re­vived.

Parnia and colleagues aim to put these re­ports to a test: spe­cif­ic sounds will be played to such pa­tients, and they’ll be asked to re­call the sounds af­ter re­viv­ing. If they do, it would con­firm the ac­counts of thoughts with­out brain ac­ti­vity—sup­port­ing the claims that “con­scious­ness is a sep­a­rate, yet un­disco­vered sci­en­tif­ic ent­ity” from the brain, Par­nia wrote in a pa­per in the the April 23 ad­vance on­line edi­tion of the re­search jour­nal Med­i­cal Hy­pothe­ses.

The study “looks like an in­ter­est­ing pro­pos­al,” wrote Da­vid Chal­mers, a phi­los­o­pher and di­rec­tor of the Cen­tre for Con­scious­ness at the Aus­tral­ian Na­tional Un­ivers­ity in Can­ber­ra, Aus­tral­ia, in an e­mail. If the claims are con­firmed, it would “pose an in­ter­est­ing chal­lenge for sci­en­tists to ex­plain,” re­marked Chal­mers, au­thor of sev­er­al books on con­scious­ness.

But it probably would­n’t set­tle the most bas­ic, long­stand­ing dis­pute: wheth­er mind and brain are dif­fer­ent things, Chal­mers added. For in­stance, even if pa­tients’ claims are ver­i­fied, they “could be due to as­pects of brain func­tion­ing dur­ing car­di­ac ar­rest that are not cap­tured by the mea­sure­ments” Par­nia is us­ing, Chal­mers wrote. These mea­sure­ments are tak­en by elec­tro­en­ce­pha­lo­gram, a tech­nique in which sen­si­tive elec­trodes at­tached to the head rec­ord elec­tri­cal brain ac­ti­vity.

Par­nia said the tri­als be­gan on a pi­lot ba­sis in Jan­u­ary at two U.K. hos­pi­tals with 10 pa­tients; he aims to ex­pand the study to oth­er coun­tries and re­cruit over 1,000 pa­tients.

Per­haps the most strin­gent test in the study is al­so the one that ad­dresses the most ex­tra­or­di­nary no­tion. Crit­ic­ally ill pa­tients some­times re­port “out-of-body” ex­pe­ri­ences in which they feel they have floated out of their own bod­ies and are watch­ing them­selves from above.

Mark well: Par­nia is not test­ing wheth­er pa­tients gen­u­inely feel their minds have floated away. He wants to test wheth­er the minds ac­tu­ally do float away—a con­tro­ver­sial idea to say the least. His team plans to place pic­tures stra­te­gic­ally around pa­tients’ rooms where they’re vis­i­ble only from near the ceil­ing. Pa­tients would la­ter be asked about the im­ages. “Thus, the claims of con­scious awareness and out-of-body ex­pe­ri­ences will be tested in­de­pen­dent­ly,” he wrote in the pa­per.

He ad­mit­ted some would find the idea out­land­ish. A study pub­lished in 2002 found that just elec­tric­ally stim­u­lat­ing spe­cif­ic brain ar­eas could trig­ger an out-of-body-like ex­pe­ri­ence—ev­i­dence to some that the sensa­t­ions are il­lu­so­ry.

Dan­iel Den­nett, di­rec­tor of the Cen­ter for Cog­ni­tive Stud­ies at Tufts Un­ivers­ity in Med­ford, Mass., wrote in an e­mail that he’s nev­er seen ev­i­dence that the events are an­ything more than hal­lu­cina­t­ions. The ex­pe­ri­ments, “if con­ducted with scru­pu­lous care,” will surely con­firm this, added Den­nett, a phil­o­so­pher who is al­so au­thor of sev­er­al books on con­scious­ness.

Yet, said Par­nia—in de­fense of the op­po­site view—pa­tients have ac­cu­rately re­ported events in their hos­pi­tal rooms that oc­curred dur­ing out-of-body ex­pe­ri­ences, while they were clin­ic­ally dead. “If we get 200 peo­ple, and all claim to have an out-of-body ex­pe­ri­ence but none can iden­ti­fy the im­ages, that would very much sup­port the idea that this is a false mem­o­ry,” Par­nia said. “If on the oth­er hand, 200 peo­ple iden­ti­fy these im­ages… then we’d have to ac­cept that may­be hu­man con­scious­ness, as bi­zarre as it may sound, could be non-local to the brain.”


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In science, plenty of problems are hard. But just one is so gruesomely trying that scientists themselves have termed it, well, “the hard problem.” How does consciousness arise—the living, aware experience of being? Some theories hold that it arises from, or is even identical to, electrical and chemical processes known to unfold in the brain. Others say it comes from something else: some yet-unknown, highly subtle brain processes, or perhaps a mind-stuff quite distinct from the brain—some call it a soul. Few on either side claim to have final answers. But they often argue passionately over who’s at least in the right playing field. Now a group of researchers have begun a study that they say might settle the issue. “We can actually test this, and put and end to all these debates,” said Sam Parnia, a critical care doctor at the Weill Cornell Medical Center in New York. Parnia has spent years studying reports that some cardiac-arrest patients keep having clear, distinct thought processes after they’re clinically dead and detectable brain activity has ceased. Patients commonly recount these mental experiences, which often include seeing a light at the end of a tunnel, after being revived. The study aims to put these reports to a test: specific sounds will be played to cardiac-arrest patients, and they’ll be asked to recall the sounds after reviving. If they do, it would confirm the accounts of thoughts without brain activity—indicating “consciousness is a separate, yet undiscovered scientific entity” from the brain, Parnia wrote in a paper in the the April 23 advance online edition of the research journal Medical Hypotheses. “It looks like an interesting proposal,” wrote David Chalmers, a philosopher and director of the Centre for Consciousness at the Australian National University in Canberra, Australia, in an email. If the claims are confirmed, it would “pose an interesting challenge for scientists to explain,” remarked Chalmers, author of several books on consciousness. But it probably wouldn’t settle the most basic, longstanding dispute, over whether mind and brain are different substances, Chalmers added. For instance, even if patients’ claims are verified, they “could be due to aspects of brain functioning during cardiac arrest that are not captured by the measurements” Parnia is using, Chalmers wrote. These measurements are taken by electroencephalogram, a technique in which sensitive electrodes attached to the head record electrical brain activity. Parnia said the trials began on a pilot basis in January at two U.K. hospitals with 10 patients; he aims to expand the study to other countries and recruit over 1,000 patients. Perhaps the most stringent test in the study is also the one that addresses the most extraordinary notion. Critically ill patients sometimes report “out-of-body” experiences in which they feel they have floated out of their own bodies and watch themselves from above. Mark well: Parnia is not testing whether patients genuinely feel their minds have floated out of their bodies. He wants to test whether the minds actually do float up. The idea is controversial to say the least. Parnia plans to place pictures strategically around patients’ rooms where they’re only visible from the ceiling. “Thus, the claims of conscious awareness and out-of-body experiences will be tested independently,” he wrote in the paper. He admitted some would find this outlandish. A study published in 2002 found that just electrically stimulating specific brain areas could trigger an out-of-body-like experience—evidence to some that the sensations are illusory, Parnia said in an interview. Daniel Dennett, director of the Center for Cognitive Studies at Tufts University in Medford, Mass., wrote in an email that he’s never seen any evidence that they’re anything other than hallucinations. Parnia’s experiments, “if conducted with scrupulous care,” will surely confirm this, added Dennett, also author of several books on consciousness. Yet Parnia said, in defense of the opposite view, that patients have accurately reported events in their hospital rooms that occurred during out-of-body experiences, while they were clinically dead. “If we get 200 people, and all claim to have an out-of-body experience but none can identify the images, that would very much support the idea that this is a false memory,” Parnia said. “If on the other hand, 200 people identify these images… then we’d have to accept that maybe human consciousness, as bizarre as it may sound, could be non-local to the brain.”