Evidence for a slow water diffusion pool swelling during activation of human visual cortex
Le Bihan D, Urayama S, Aso T, Hanakawa T, Fukuyama H
Kyoto University Graduate School of Medicine, CEA
SynopsisA transient decrease of water diffusion has been reported during activation of visual cortex. We have investigated signal changes at different degrees of diffusion sensitization using a 2-compartment diffusion model. At 3T activation of visual cortex was detected in our 6 subjects though a diffusion-weighted signal increase, but the signal change increased with b value. This increase was well modeled by a swelling of the slow diffusion pool (+0.56%) and a shrinking of the fast diffusion pool (-0.44%), suggesting a shift of water from the fast to the slow diffusion pools. Although the nature of the pools is still unclear diffusion-sensitized MRI might provide direct and quantitative access to a physiological surrogate of cortical activation.