The accuracy of predicted blood-oxygen-level dependent (BOLD) signals from electrocorticographic (ECoG) components.
The correlation between ECoG and BOLD was calculated for a V1 site and a V2 site. The locations of one sample electrode in V1 and one in V2 are indicated by the enlarged white discs on the cortical surface for subject 1. (A) In a foveal V1 site, the broadband ECoG amplitude accurately predicted the BOLD signal (left). Error bars show 68% confidence intervals across bootstraps. Narrowband gamma power (center) and alpha power (right) were uncorrelated with BOLD. (B) In a V2 site, the broadband ECoG was weakly correlated with BOLD (left). Narrowband gamma did not predict BOLD (middle). Alpha was negatively correlated with BOLD (right). Scatter plots for all other V1 and V2/V3 sites are shown in S5 Fig. (C-D) The same as A and B but for simulated neuronal population data fit to the V1 and V2 ECoG data. For all panels: data points are the bootstrapped median across 30 trials per stimulus (ECoG) and across scans (BOLD). The trend lines are least square fits to the 8 data points plotted. The R2 values are the coefficient of determination computed by cross-validation, with a regression fit to half the data and evaluated on the other half. The black outlines indicate the regressions that show reliable predictors of the BOLD signal—broadband in V1, broadband and alpha in V2/V3. (Code to download data and reproduce this figure can be found on https://github.com/dorahermes/Paper_Hermes_2017_PLOSBiology function ns_script09A_Fig8AB_Fig9AB.m and function ns_script07B_Fig7AB_Fig8CD.m).
