Toshihiko Aso1, Cyril Poupon1, Shin-ichi Urayama2, Hidenao Fukuyama2, Denis Le Bihan2,3
1NeuroSpin, I2BM/DSV/CEA, Gif-sur-yvette, France; 2Human Brain Research Center, Kyoto University Graduate School of Medicine, Kyoto, Japan; 3NeuroSpin, I2BM/DSV/CEA, Gif-sur-yvette,, France
Visual activation can be detected with heavily sensitized diffusion-fMRI (DfMRI). The striking temporal precedence of the diffusion response to BOLD suggests a non-vascular source. However, a residual tissue T2 component sensitive to vascular (BOLD) effects also remains present in the DfMRI signal.The purpose of this study was to build a DhRF response function optimized for DfMRI taking into account both diffusion and vascular dynamics, and to evaluate it in an ultra-short event-related stimulation mode. This DhRF was shown to better predict activation in DfMRI data than the usual HRF, offering an improved sensitivity and specifity. The overall temporal precedence of the DfMRI signal over BOLD-fMRI was confirmed with those ultra-short event-related paradigms.