"When we direct our attention to such specific locations or events -- in this case, the bicyclist off to the side -- we tend to more quickly discriminate or detect changes there than at other locations in our visual field that are not so attended," Woldorff said.
Previous studies, including several by the Duke researchers, have associated such attentional processes with brain activity that occurs in what is called the "frontal-parietal attentional control network." This network comprises areas of nerve cells located in the front portion and the upper rear, or parietal, portion of the brain.
Previous studies also have indicated that areas of the visual cortex, located in the lower rear part of the brain, preferentially process information coming from locations or objects in the visual field where attention is directed.
Those studies have additionally suggested that the frontal-parietal network may induce this improved processing in the visual areas by means of some "biasing" or enhancing signal.
But "little is known about the timing and sequence of activations within this frontal-parietal network and their temporal relationship to any such biasing," the Duke scientists said in their report.
They said the uncertainty about such characteristics is due mainly to specific technical limitations of two of the main technologies currently used to monitor brain activity in humans: functional magnetic resonance imaging (fMRI) and event-related potential (ERP) recordings.
Although fMRI can pinpoint the locations of such brain activity by measuring changes in regional blood flow associated with increased neural activity, the technology is "very limited as
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Contact: Monte Basgall
monte.basgall@duke.edu
919-681-8057
Duke University
3-Jan-2007