The BOLD signal is linked to neural activity through the canonical hemodynamic response function (HRF), often assumed to be static across both brain area and brain state. We employed simultaneous EEG-FMRI recordings to investigate the hemodynamic response to neural activity in the alpha, beta, and gamma frequency bands. We find that the shape of the HRF depends on both brain region, and brain state. Default mode network (DMN) BOLD signals are linked to alpha synchronization, while occipital BOLD signals are linked to alpha/beta desynchronization and gamma synchronization. Connectivity estimates assuming a canonical HRF may be biased by HRF differences across region and state.
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