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“Vegetative” patient can think, study suggests

Sept. 11, 2006
Special to World Science  

An out­ward­ly un­re­spon­sive pa­tient di­ag­nosed as be­ing in a veg­e­ta­tive state was ca­pa­ble of un­der­stand­ing and re­spond­ing to some in­struc­tions in a new brain-imaging stud­y, ac­cord­ing to re­search­ers.

Sci­en­tists said the finding sug­gests con­scious­ness ex­ists in some pa­tients who were thought to lack it. But they cau­tioned that this case might not ap­ply to oth­ers be­cause each brain in­ju­ry is dif­fer­ent.

Nonetheless, they said, it’s a step toward providing information for families of vegetative and comatose patients worldwide, who wonder daily whether their injured relative can understand them. 

A study published last year found that some nearly coma­tose pa­tients clas­si­fied as be­ing in a “mi­ni­mal­ly con­scious state” have signs of aware­ness

In the new research, Adri­an Ow­en of the Med­i­cal Re­search Coun­cil in Cam­bridge, U.K. and col­leagues used func­tion­al Mag­net­ic Res­o­nance Im­ag­ing tech­nol­o­gy to meas­ure the brain re­sponses of a pa­tient who was instead in a “per­sist­ent veg­e­ta­tive state.” 

The 23-year-old wom­an had suf­fered a se­vere trau­mat­ic brain in­ju­ry in a traf­fic ac­ci­dent. Af­ter an in­i­tial co­ma, she opened her eyes and showed nor­mal sleep-wake cy­cles, re­search­ers said. But she re­mained “un­re­spon­sive” and lack­ing in “spon­ta­neous, in­ten­tion­al be­hav­iors,” ac­cord­ing to doc­tors—markers of a veg­e­ta­tive state. She had been this way for five months at the time of the study. 

Her brain re­sponses to spo­ken sen­tences were sim­i­lar to those of healthy vol­un­teers, the re­search­ers re­ported, but these re­sponses are thought to be rel­a­tively au­to­mat­ic and have been elicited from oth­er un­con­scious sub­jects. 

In­ves­ti­gat­ing fur­ther, the au­thors asked the pa­tient to im­ag­ine her­self play­ing ten­nis and vis­it­ing all of the rooms in her house. Again, her brain re­sponses close­ly matched those of healthy vol­un­teers, they not­ed. The find­ings ap­pear in the Sept. 8 is­sue of the re­search jour­nal Sci­ence.

The “find­ings in­di­cate the ex­ist­ence of a rich men­tal life, in­clud­ing au­di­to­ry lan­guage pro­cess­ing and the abil­i­ty to per­form men­tal im­age­ry tasks,” wrote Li­o­nel Nac­cache of the Na­tion­al In­sti­tute for Health and Med­i­cal Re­search in Or­say, France, in a com­men­tary in the jour­nal.

But Nac­cache and Ow­en said it’s im­por­tant not to gen­er­al­ize from this sin­gle pa­tient to most oth­er veg­e­ta­tive-state pa­tients. “This is un­like­ly the case for all veg­e­ta­tive pa­tients. It’s such a het­er­o­ge­ne­ous group; they all have brain in­ju­ries of dif­fer­ent type­s,” Ow­en said.

Functional Magnetic Resonance Imaging, or fMRI, is a sys­tem for mea­sur­ing blood flow in the brain using ra­dio waves and a strong mag­ne­tic field.


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Homepage image: The brain of a healthy volunteer scanned by fMRI when the volunteer is asked to think of playing tennis.

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