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Schlagwörter:
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Zusammenfassung:
Most fMRI studies are based on the detection of a positive BOLD response (PBR). A few previous human studies indicated the existence of negatively responding voxels in brain regions remote from the focus of PBR (1, 2, and others). Recent studies in the anesthetized cat (3) and monkey (4) have demonstrated adjacent PBR and negative BOLD response (NBR). In this study we demonstrate sustained (different from the "initial dip") negative BOLD response (NBR) that occurs concurrently with and is coupled to the positive response, via a mechanism that involves a reduction in blood flow (CBF) to the less demanding regions in the human brain.
