Explained variance in the blood-oxygen-level dependent (BOLD) functional magnetic resonance imaging (fMRI) signal in the simulations and in data.

(A) Variance in the measured BOLD signal explained by broadband, gamma, and alpha changes in the electrocorticographic (ECoG) data. The colored box plots show the variance explained by each of the 7 model types: black bar = median, upper and lower boxes = quartiles, and error bars = data range excluding outliers (outliers plotted as red plusses). The R² was cross-validated (split between subjects for BOLD and stimulus repetitions for ECoG) to ensure that the R² can be compared between models with different numbers of explanatory variables. Gray dashed lines indicate the noise floor (R² when shuffling the BOLD labels in the training data), and the solid gray lines indicate the data-to-data reliability for the BOLD signal. Bottom: the regression coefficients show whether the broadband, gamma, and alpha signals were positive or negative predictors of the BOLD signal. A red * in the lower plot indicates whether regression coefficients differed significantly from 0 by a bootstrap test (p < 0.05). (B) The same as A but for the 13 V2/V3 electrodes. (C) The same as A but for the 9 simulations fitted to V1 data. The R² was cross-validated (split between even and odd stimulus repetitions). D) Same as C, except for the 13 simulations fitted to the V2/V3 data. (Code to download data and reproduce this figure can be found on https://github.com/dorahermes/Paper_Hermes_2017_PLOSBiology).