P>When particular regions of the brain increase their neural activity in association with various actions or thought processes, they emit enhanced blood oxygen level dependent signals. The signals can be localized in the brain and translated into digital images that portray neural activity level as a ratio of oxygenated to de-oxygenated hemoglobin, the iron-containing pigment in red blood cells. Researchers then can quantify these signals to generate maps of various brain functions.

Fifty-two study participants were divided into four groups: "ultra-high-risk," where participants experience symptoms but the illness is not full-blown; early schizophrenia, where participants have had the illness less than five years; chronic schizophrenia, where participants have had the illness for more than five years; and healthy age-matched "controls," for comparison.

Those at ultra-high-risk had been pre-screened for schizophrenia symptoms, revealing that some were showing early emotional, affective and cognitive symptoms such as the blunting of emotion, poor personal relationships, poor hygiene, emotional detachment and false beliefs.

While undergoing fMRI scans, all participants responded to an executive decision test - so-called because decision making and task-appropriate response selection are required - displayed on a computer screen. This test, developed by the study team, requires push-button responses to certain colored squares, circles and objects from everyday life. Each visual cue is presented at a fraction of a second against a white background, and participants must ignore an auditory tone sounded when each cue is presented.

"Of particular interest was the neural activity generated by a series of infrequent circles that were designated as 'target' events, which participants were instructed to detect and respond to as quickly as possible by pressing a button," Belger said.

"Accurate and fast performance on this test requires both the mainte
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Contact: L.H. Lang
llang@med.unc.edu
919-843-9687
University of North Carolina School of Medicine
16-Mar-2005

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