Localization of cardiac-induced signal change in fMRI

Signal detection in the analysis of blood oxygen level-dependent (BOLD) fun ctional magnetic resonance imaging (fMRI) may be greatly hindered by cardia c pulsatility artifacts. Vessel pulsation, cerebrospinal fluid movement, an d tissue deformation are all associated with the cardiac cycle and all can produce fMRI signal variance. Most cognitive fMRI studies do not utilize a method of cardiac-related noise reduction, in part because of the lack of i nformation on the regional significance and magnitude of cardiac-related si gnal variance in the brain. In this paper we present a topographical descri ption of the regions showing significant contributions of cardiac-related s ignal variance. The results are highly consistent across subjects and sugge st that reduced sensitivity due to cardiac-induced noise in the BOLD signal is systematically greater in specific areas, typically near major blood ve ssels. Significant effects of cardiac-related variability were found on ave rage in 27.5 +/- 8.0% of voxels. Strong influences were found along the ver tebrobasilar arterial system near the medial areas of the brain, along the middle cerebral artery near the anterior temporal lobes and in the insula, and along the anterior cerebral artery in the anterior interhemispheric fis sure in the medial frontal lobes. Significant effects were also observed in the sigmoid transverse and superior sagittal sinus regions. These results identify regions in which fMRI mill have reduced sensitivity due to increas ed signal variation produced by cardiac pulsatility.