Temporal Dynamics of the BOLD Impulse Response

J. A. de Zwart, A. C. Silva, P. van Gelderen, P. Kellman, M. Fukunaga, R. Chu, A. P. Koretsky, J. H. Duyn LFMI, NINDS, National Institutes of Health, Bethesda, MD, United States, LCE, NHLBI, National Institutes of Health, Bethesda, MD, United States Introduction BOLD fMRI allows an indirect measurement of neuronal activity. Its contrast mechanism is based on the intravascular change in deoxyhemoglobin concentration and its transit through the cerebral vasculature. This has implications for its spatial and temporal resolution which are believed to be a few mm [1] and 4-7 s [2], respectively. In this study, we hypothesized that the BOLD temporal and spatial resolution are both limited by vascular transit effects. We use a previously described model of the venous architecture [3] to simulate the impulse response function of vascular transit, and compared the results with high resolution impulse response measurements in humans.