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Schizophrenia reassessed as fixation on self

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Schizophrenia reassessed as fixation on self

Jan. 23, 2009
Courtesy Massachusetts
Institute of Technology
and World Science staff

Schiz­o­phre­nia may blur the bound­a­ry be­tween in­ter­nal and ex­ter­nal real­i­ties by over­ac­ti­vat­ing a brain sys­tem in­volved in self-re­flec­tion, caus­ing an ex­ag­ger­at­ed fo­cus on self, a study has found.

The tra­di­tion­al view of schiz­o­phre­nia is that the dis­turbed thoughts, per­cep­tions and emo­tions char­ac­ter­iz­ing the men­tal ill­ness result from dis­con­nec­tions among the brain re­gions that con­trol these dif­fer­ent func­tions.

But the new stu­dy found that schiz­o­phre­nia al­so in­volves ex­cess con­nec­ti­vity be­tween brain re­gions in­volved in self-re­flec­tion which be­come ac­tive when we think of noth­ing in par­tic­u­lar, or of our­selves.

“Peo­ple nor­mally sup­press this ‘de­fault’ sys­tem when they per­form chal­leng­ing tasks. But we found that pa­tients with schiz­o­phre­nia don’t,” said John D. Ga­bri­e­li of the Mas­sa­chu­setts In­sti­tute of Tech­nol­o­gy, one of 13 au­thors of the study, published Jan. 19 in the ad­vance on­line is­sue of the research journal Pro­ceed­ings of the Na­tional Acad­e­my of Sci­ences.

The findings “may re­flect an in­abil­ity of peo­ple with schiz­o­phre­nia to di­rect men­tal re­sources away from in­ter­nal thoughts and feel­ings and to­ward the ex­ter­nal world,” said MIT’s Su­san Whitfield-Ga­bri­e­li, al­so a co-author.

John Ga­bri­e­li added that he hopes the re­search might lead to ways of pre­dict­ing or mon­i­tor­ing in­di­vid­ual pa­tients’ re­sponse to treat­ments for the ill­ness, which oc­curs in about one per­cent of peo­ple.

Schiz­o­phre­nia is largely ge­net­ic. First-degree rel­a­tives of pa­tients (their par­ents, broth­ers, sis­ters, or chil­dren) are 10 times more likely to de­vel­op the dis­ease than the gen­er­al popula­t­ion. Which genes are re­spon­si­ble are largely un­known.

The re­search­ers stud­ied three matched groups of 13 sub­jects each: schiz­o­phre­nia pa­tients, non­psy­chot­ic first-degree rel­a­tives of pa­tients and healthy nonrel­a­tives. They chose re­cently di­ag­nosed pa­tients, so that dif­fer­ences in pri­or treat­ment or psy­chot­ic episodes would­n’t bi­as the re­sults.

The par­ti­ci­pants were brain-scanned us­ing a widely used tech­nique known as func­tion­al mag­net­ic res­o­nance im­ag­ing, while rest­ing and while per­forming easy or hard mem­o­ry tasks.

The re­search­ers fo­cused on the “de­fault” sys­tem, a net­work of brain re­gions whose ac­ti­vity drops when peo­ple per­form hard men­tal tasks. This net­work in­cludes ar­eas of the out­er brain known as the me­di­al pre­fron­tal cor­tex and the pos­te­ri­or cin­gu­late cor­tex, as­so­ci­at­ed with self-re­flec­tion and mem­o­ries about the self. The net­work ap­pears to be­come linked to­geth­er and ac­tive when the mind wan­ders.

The sci­en­tists found that in the schiz­o­phre­nia pa­tients, the de­fault sys­tem was both hyperac­tive and hy­per­con­nected dur­ing rest, and it re­mained so as they per­formed the mem­o­ry tasks. In oth­er words, the pa­tients were less able than healthy sub­jects to sup­press the net­work’s ac­ti­vity dur­ing the task. Interest­ingly, the less the sup­pression and the great­er the con­nec­ti­vity, the worse they per­formed on the hard mem­o­ry task, and the worse their symp­toms.

The hyperac­tive de­fault sys­tem could al­so help to ex­plain hal­lu­cina­t­ions and par­a­noia by mak­ing neu­tral ex­ter­nal stim­u­li seem in­ap­pro­pri­ately self-relevant, the in­ves­ti­ga­tors said. For in­stance, if brain re­gions whose ac­ti­vity nor­mally sig­ni­fies self-fo­cus are ac­tive while lis­ten­ing to a voice on tel­e­vi­sion, the per­son may per­ceive that the voice is speak­ing di­rectly to them.

The de­fault sys­tem was al­so overac­tive, though less so, in first-degree rel­a­tives of schiz­o­phre­nia pa­tients who did­n’t them­selves have the dis­ease, the re­search­ers said. This sug­gests overac­tiva­t­ion of the de­fault sys­tem may be linked to the ge­net­ic cause of the dis­ease rath­er than to its con­se­quenc­es, they added. The de­fault sys­tem is a hot top­ic in brain im­ag­ing, said John Ga­bri­e­li, partly be­cause it’s easy to meas­ure and is af­fect­ed in dif­fer­ent ways by dif­fer­ent dis­or­ders.

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