Precise temporal localizations are difficult in traditional fMRI studies due to the slow, diffuse, and indirect nature of the BOLD measurement and to spatial variations in the HRF. Our method of combining single-trial EEG variability with fMRI was able to circumvent this limitation by finding BOLD correlates of the electrophysiological response at multiple temporal offsets. Because we used EEG STV in our fMRI model design and orthogonalized to event-related regressors, our activations reveal the BOLD correlates of endogenous modulations in attention across trials. This method begins to unravel a complex cascade of neural events, including sensory processing, executive processing, motor planning, and default-mode activity, in high spatial and temporal resolution.
