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Mark W. Greenlee, Gabriele Frank, Oliver Baumann; Cortical activation during triple-step memory-guided saccadic eye movements as measured by fMRI. Journal of Vision 2006;6(6):499. doi: 10.1167/6.6.499.
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Blood oxygenation level dependent (BOLD) contrast was measured using event-related fMRI in subjects while they performed visually guided (VGS) and memory guided (MGS) triple-step saccades to three eccentric targets presented sequentially left or right of central fixation. Saccadic eye movements were recorded with a fiber-optic limbus-tracking technique in the MR scanner. Responses during VGS were compared to those evoked during MGS, in which the subject performed saccades to each of three remembered locations. To explore the role of dorsolateral prefrontal cortex (DLPFC) in the manipulation of the contents of working memory, the sequence of saccade targets in the MGS task was either constant or was manipulated in a color-sequence recoding phase. Saccade-related BOLD responses in prefrontal, premotor, parietal and occipital areas depend on the type of task performed. More pronounced activation in DLPFC was found only during the color-recoding phase of each trial for that condition and not during the maintenance of spatial locations. This finding suggests that DLPFC is primarily involved in the manipulation, and to a lesser extent, the maintenance of the contents of working memory. The results support the process-specific model of DLPFC, where the manipulation and reorganization of the contents of working memory is emphasized. Maintenance of the contents of visual working memory appears to be supported by neural populations in the parietal and occipital cortex.
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