Fig. S1.

Phase-shift properties of the fMRI response. (A) Simulation with a canonical model. The oscillation around the plateau is expected to become extremely small when the stimulus frequency is 0.5 Hz. (B) Schematic of expected phase delays. When the HRF is convolved with oscillatory neural activity, and the period of neuronal activity fluctuations is short relative to the duration of the HRF, the phase of the response can shift substantially relative to the input oscillation. a.u., arbitrary units. (C) Simulation of the expected response at different stimulation frequencies with a range of HRFs. For each HRF, the phase of the response differs across stimulation frequencies, because the phase wraps relative to the stimulation frequency. The phase shifts induced by these physiologically plausible hemodynamics are in the same range as those we observed in the data, with precise values varying depending on the shape of the HRF.