Inter-Areal and Inter-Individual Variations in Diffusion-Weighted FMRI Signal

Toshihiko Aso¹, Shin-ichi Urayama¹, Hidenao Fukuyama¹, Denis Le Bihan, ¹²

Neuronal activation can be detected with heavily sensitized diffusion-fMRI (DfMRI). The striking temporal precedence of the diffusion response to BOLD in the visual cortex suggests a non-vascular source. A visual working memory task was implemented to investigate DfMRI responses outside visual cortex. We found very similar response patterns between well separated cortices showing temporal precedence over BOLD, while large individual variations were observed with BOLD responses. Discrepancies between DfMRI and BOLD responses were also observed, such as negative BOLD signals accompanying positive DfMRI responses supporting the assumption that the DfMRI and BOLD responses have different origins.