Accuracy of predicted blood-oxygen-level dependent (BOLD) signals from simulated neuronal activity.

(A) Simulated BOLD (x-axis) versus measured BOLD (y-axis) for a V1 site. Each color corresponds to one stimulus condition (red dots, grating patterns; blue dots, noise patterns; black dot, uniform stimulus, or blank). Error bars indicate 68% confidence intervals, bootstrapped 100 times over 30 trials per stimulus for simulation and over repeated scans for BOLD data. (B) The same as A but for a V2 site. (C) The accuracy of BOLD predictions for all V1 and V2/V3 sites. Each site is indicated by a yellow dot. The orange lines show the medians and the red boxes the 0.25 and 0.75 quantiles. The thin, gray, solid lines show the BOLD data-to-data reliability, and the gray dashed lines show the accuracy when the BOLD data and trial conditions are shuffled in the training dataset. Accuracy is quantified as the coefficient of determination after subtracting the mean from the data and the predictions, and dividing each variable by its vector length. Because the simulations were fit to electrocorticographic (ECoG) data and tested on BOLD data, the predictions are cross-validated, and the coefficient of determination spans (−∞,1]. A value of −1 is expected when the data and predictions are unrelated and have equal variance, as in the case of the shuffled control analysis. (Code to reproduce this figure can be found on https://github.com/dorahermes/Paper_Hermes_2017_PLOSBiology function ns_script07.m).