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Abstract:
In a previous study, we have shown that in human subjects it is possible to detect blood oxygenation level dependent (BOLD) signal changes evoked by a visual stimulus presented only for 5 ms. Moreover, we observed that at this ultrashort stimulus duration a) the response is highly non-linear compared to 50ms, 250ms and 1s stimulus b) the extrapolated intercept at 0ms stimulus duration was not zero. That is, below specific stimulus duration
the hemodynamic response remains constant. In this study, we have expanded our previous investigation on the temporal behaviour of the BOLD response by zooming into the time scale of stimulus durations as short as 0.1 to 5ms, in order to evaluate if there is indeed a minimum hemodynamic
response. Moreover, in order to gain insights about the dynamics of neural response at ultrashort stimulus durations, we also performed VEP recordings to complement the fMRI data.
