Spatial dependence of the nonlinear BOLD response at short stimulus duration
- Pfeuffer, J.
- McCullough , J.
- de Moortele , P.
- Ugurbil, K.
- Hu, X.
DOIAbstract
Most functional magnetic resonance imaging studies use linear models to predict the measured response by convolution of an impulse response with the stimulus profile. Using very short visual presentation times (<2 s), deviation from the linear model in the measured BOLD data from the human brain was found for the response integral, amplitude, and width. In this study, high temporal and spatial resolution were used to quantify nonlinear effects and investigate the spatial dependence. Data at 4 Tesla showed at short stimulus duration a nonlinearity, i.e., deviation from a linear model, with an index up to 400, whereas data at 7 Tesla exhibited a nonlinearity index up to 40. The effect was more pronounced for response amplitude than for respon...
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