Effect of HRF Spatial Variability on the Accuracy of Multivariate Granger Causal Networks Obtained from FMRI Data

Gopikrishna Deshpande¹, Xiaoping Hu¹

The hemodynamic response of fMRI is known to vary across brain regions. This has the potential to confound inferences about neuronal causality obtained from Granger causality analysis of fMRI. We investigated this aspect in a multivariate model using a simulated neuronal system. The results suggest that Granger causality inferred from fMRI data had accuracies well above chance and up to 90%, provided the data had low measurement noise, was sampled at a TR less 2 s, the causal influences were strong and the hemodynamic delay variation is within its normal physiological range.