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Abstract #2784

Hemodynamics and nonlinearities of BOLD response to ultrashort visual stimulation (5ms - 1s)

Ugurbil K, Yesilyurt B, Uludag K
Center for Magnetic Resonance Research, Max-Planck-Institute for biological Cybernetics

It has generally been suggested that one cannot temporally resolve alterations in neural activity in the range of milliseconds using BOLD signal since hemodynamic response evolves in seconds. However, in this study using ultrashort visual stimulus durations ranging from 5 milliseconds to 1 second we investigated the hemodynamic response and nonlinearity of BOLD response. We were able to show that 1) a BOLD response to stimulus durations as short as 5 ms is detectable in humans; b) BOLD responses to different stimulus durations are highly non-linear and c) non-linearities depend not only to stimulus duration but also on intensity.