[Futurework] Researchers measure consciousness through brain activity

[Steve Kurtz]

Dematerialized consciousness takes another hit. Steve http://www.world-science.net/othernews/130814_consciousness "Long before it's in the papers" August 14, 2013 RETURN TO THE WORLD SCIENCE HOME PAGE Researchers measure consciousness through brain activity Aug. 14, 2013 Courtesy of Science Translational Medicine and World Science staff A new study seems to back up pre­vi­ous pro­pos­als that the lev­el of com­plex­ity of your brain ac­ti­vity largely de­ter­mines wheth­er you’re con­scious or not. Sci­en­tists de­vel­oped a test of con­sciousness based on the con­cept—a test that does­n’t re­quire a pa­tient to ac­tu­ally do an­y­thing, they said. Con­scious­ness is elu­sive, but we know it’s what van­ishes when we fall in­to a deep sleep and reap­pears when we wake up. Doc­tors typ­ic­ally de­ter­mine if a per­son is con­scious by their abil­ity to pro­cess and re­spond to ex­ter­nal com­mands, such as “open your eyes” or “squeeze my hand.”  But these meth­ods are su­per­fi­cial, as re­search has shown in the last dec­ade that a brain to­tally dis­con­nect­ed from the out­side world may still have some aware­ness. This may hap­pen in brain-injured pa­tients who emerge from a co­ma but can’t move or un­der­stand in­struc­tions, for ex­am­ple. One the­o­ry is that in a con­scious brain, dif­fer­ent popula­t­ions of neu­rons, or nerve cells, car­ry out their own com­puta­t­ional roles, but can’t com­mu­ni­cate with oth­er neu­ron popula­t­ions. When the brain loses com­plex­ity, some sci­ent­ists pro­pose, neu­rons ei­ther start to be­have more si­m­i­larly al­to­geth­er (re­sult­ing in a loss of in­forma­t­ion), or their abil­ity to com­mu­ni­cate is im­paired (re­sult­ing in a loss of in­tegra­t­ion). For ex­am­ple, if you’re asleep and you hear a dog bark­ing, your brain will re­spond with ac­ti­vity in the au­di­to­ry cor­tex, the part of the brain that pro­cesses sound. But if you’re awake, the same sound might al­so in­duce thoughts of your own dog, or an­noy­ance at the loud­ness of the bark—re­sponses tied to ac­ti­vity in the brain’s mem­o­ry and emo­tion cen­ters.  These lat­er brain pro­cesses con­tain more in­forma­t­ion. Neu­ro­sci­en­tists have been try­ing to de­vel­op ways to meas­ure con­sciousness based on this brain com­plex­ity. In the stu­dy, Mar­cel­lo Mass­mini of the Uni­vers­ity of Mi­lan in Italy and col­leagues de­vised a tech­nique to meas­ure this brain com­plex­ity, or how much in­tegra­t­ion and in­forma­t­ion flow is hap­pening in the brain. Called the Per­turba­t­ional Com­plex­ity In­dex or PCI, their tech­nique in­volves mildly “shak­ing” the whole brain with a strong mag­net­ic stimula­t­ion and re­cord­ing the re­sponse of neu­rons. This da­ta can then be used to cal­cu­late how much in­forma­t­ion the brain is able to pro­duce as a whole.  The re­search­ers tested the tech­nique in pa­tients with brain in­ju­ries, pa­tients un­der an­es­the­sia with dif­fer­ent drugs, and in pa­tients who were awake, in deep sleep or dream­ing. The test re­flected the par­ti­ci­pants’ lev­el of con­sciousness un­der each of these con­di­tions, they found.  The re­sults sug­gest that dif­fer­ent lev­els of con­sciousness are tightly linked to the com­plex­ity of the brain re­sponse, they added. For ex­am­ple, find­ing a “PCI val­ue” above the sleep or an­es­the­sia lev­el in a pa­tient who is oth­erwise un­re­spon­sive would sug­gest she or he is con­scious to some ex­tent. Al­though more re­search is needed, the anal­y­sis could po­ten­tially be a use­ful tool at the hos­pi­tal bed­side for meas­ur­ing con­sciousness, they added. The find­ings are pub­lished in the Aug. 14 is­sue of the jour­nal Sci­ence Transla­t­ional Med­i­cine. * * * Send us a comment on this story, or send it to a friend

_______________________________________________
Futurework mailing list
Futurework@lists.uwaterloo.ca
https://lists.uwaterloo.ca/mailman/listinfo/futurework