Fig. 7.

Accounting for vascular lags can further improve the resolution of fMRI oscillations. (A) Responses of early-responding and late-responding voxels across stimulus frequencies in an individual subject. The phase delays persist across conditions, and the fMRI response is larger in the later-responding voxels. (B) Early- and late-responding voxels plotted for a subject in experiment 3. At 0.75 Hz, the lags across voxels introduce phase cancellation of the fMRI response. The shaded region shows the SE across cycles. (C) The mean oscillatory response across all subjects in experiment 3 declines more in late-responding voxels and is stronger in early-responding voxels at high frequencies. The black dashed line is the prediction of the canonical linear model. (D) Mean time series across subjects in experiment 3 demonstrates that analyzing the early voxels separately results in larger oscillations than are detectable when averaging across the whole V1 ROI (n = 5 subjects, 60 runs). The shaded region is standard error across runs. (E) Heterogeneous spatial distribution of lags in individual voxels. The image is from a representative subject. Color indicates the phase lag in each voxel in the localizer run.