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3D film captures line between consciousness and lights-out

June 10, 2011
Courtesy of the University of Manchester
and World Science staff

New 3D film clips show what hap­pens as a brain goes un­con­scious—of­fer­ing sci­en­tists what they call an un­prec­e­dent­ed peek in­to the phys­i­cal na­ture of that mys­te­ri­ous state, con­scious­ness.

Rea­son­ing that use­ful in­sights could come from an­y­thing that shows what sep­a­rates con­scious­ness from un­con­scious­ness, re­search­ers filmed brains with a new type of scan­ning de­vice while an an­es­thet­ic took ef­fect on vol­un­teers.

An image from the fEITER brain scan­ning de­vice. (Cour­tesy U. of Man­chest­er)


An­es­the­si­olog­ist Bri­an Pol­lard of the Un­ivers­ity of Man­ches­ter, U.K. said the real-time im­ages seem to show that los­ing con­scious­ness in­volves a change in elec­tri­cal ac­ti­vity deep in the brain. The pro­cess al­ters the ac­ti­vity of cer­tain groups of nerve cells and hin­ders com­mu­nica­t­ion be­tween dif­fer­ent parts of the brain, he ex­plained.

He added that the find­ings seem to sup­port a hy­poth­e­sis put for­ward by Su­san Green­field of the Un­ivers­ity of Ox­ford about the na­ture of con­scious­ness. Green­field sug­gests con­scious­ness arises from dif­fer­ent groups of brain cells, called neu­ral as­sem­blies, that work ef­fi­ciently to­geth­er, or not, de­pend­ing on the avail­a­ble stimula­t­ions. Con­scious­ness is not an all-or-none state but more like a dim­mer switch, she ar­gues, chang­ing ac­cord­ing to growth, mood or drugs. 

When some­one is anes­thetized, Pol­lard said, it seems small neu­ral as­sem­blies ei­ther work less well to­geth­er or in­hib­it com­mu­nica­t­ion with oth­er neu­ral as­sem­blies. “Our find­ings sug­gest that un­con­scious­ness may be the in­crease of in­hib­itory as­sem­blies across the brain’s cor­tex,” the out­er and more ad­vanced re­gion of the brain, he said. “These find­ings lend sup­port to Green­field’s hy­poth­e­sis.”

The team used a new im­ag­ing meth­od, in­vented at the uni­ver­sity, whose name is a mouth­ful even by the stan­dards of the al­ready long acronyms now used for some brain-scan­ning teh­niques. It’s called func­tion­al elec­tri­cal im­ped­ance to­mog­ra­phy by evoked re­sponse, or fEITER. It’s de­signed to en­a­ble high-speed im­ag­ing and mon­i­tor­ing of elec­tri­cal ac­ti­vity deep with­in the brain.

“We have looked at 20 healthy vol­un­teers and are now look­ing at 20 anes­thetized pa­tients sched­uled for surgery,” said Pol­lard, who pre­s­ented re­sults at the Eu­ro­pe­an An­aes­the­sia Con­gress in Am­ster­dam June 11. “We are able to see 3-D im­ages of the brain’s con­duc­ti­vity change, and those where the pa­tient is be­com­ing anes­thetized are most in­ter­est­ing.”

“We have been able to see a real time loss of con­scious­ness in an­a­tom­ic­ally dis­tinct re­gions of the brain for the first time,” he added. “We still do not know ex­actly what hap­pens with­in the brain as un­con­scious­ness oc­curs, but this is anoth­er step in the di­rec­tion of un­der­stand­ing the brain and its func­tions.”

The new im­ag­ing meth­od could “make a huge im­pact on many ar­eas of im­ag­ing in med­i­cine. It should help us to bet­ter un­der­stand an­es­the­sia, seda­t­ion and un­con­scious­ness, al­though its place in med­i­cine is more likely to be in di­ag­nos­ing changes to the brain that oc­cur as a re­sult of, for ex­am­ple, head in­ju­ry, stroke and de­men­tia,” he added. “The big­gest hur­dle is work­ing out what we are see­ing and ex­actly what it means.”


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A new 3D film shows what happens as a brain goes unconscious—offering scientists what they call an unprecedented peek into the physical workings of that mysterious state, consciousness. Reasoning that useful insights could come from anything that shows what separates consciousness from unconsciousness, researchers made the movie with brain scanning equipment while an anaesthetic took effect on volunteer patients. Anaesthesiologist Brian Pollard of The University of Manchester, U.K. said the real-time images seem to show that losing consciousness involves a change in electrical activity deep in the brain. The process alters the activity of certain groups of nerve cells and hinders communication between different parts of the brain, he explained. He added that the findings seem to support a hypothesis put forward by Susan Greenfield of the University of Oxford about the nature of consciousness. Greenfield suggests consciousness arises from different groups of brain cells, called neural assemblies, that work efficiently together, or not, depending on the available stimulations. Consciousness is not an all-or-none state but more like a dimmer switch, she argues, changing according to growth, mood or drugs. When someone is anaesthetised, Pollard said, it seems small neural assemblies either work less well together or inhibit communication with other neural assemblies. “Our findings suggest that unconsciousness may be the increase of inhibitory assemblies across the brain’s cortex,” the outer and more sophisticated region of the brain, he said. “These findings lend support to Greenfield’s hypothesis.” The team used a newly developed imaging method whose name is a mouthful, even by the standards of the already long acronyms now used for some brain-scanning tehniques. It’s called functional electrical impedance tomography by evoked response, or fEITER. It’s designed to enable high-speed imaging and monitoring of electrical activity deep within the brain. “We have looked at 20 healthy volunteers and are now looking at 20 anaesthetised patients scheduled for surgery,” said Pollard, who is scheduled to present results at the European Anaesthesiology Congress in Amsterdam June 11. “We are able to see 3-D images of the brain’s conductivity change, and those where the patient is becoming anaesthetised are most interesting.” “We have been able to see a real time loss of consciousness in anatomically distinct regions of the brain for the first time,” he added. “We still do not know exactly what happens within the brain as unconsciousness occurs, but this is another step in the direction of understanding the brain and its functions.” The new imaging method could “make a huge impact on many areas of imaging in medicine. It should help us to better understand anaesthesia, sedation and unconsciousness, although its place in medicine is more likely to be in diagnosing changes to the brain that occur as a result of, for example, head injury, stroke and dementia,” he added. “The biggest hurdle is working out what we are seeing and exactly what it means.”