Figure 2. Conditional Pairwise Granger Causality In a Three Neuron Network.

If pairwise Granger causality were applied to determine the connectivity of both of these network configurations the results for both would resemble panel a). Using pairwise Granger causality alone, it is not possible to differentiate between these network configurations. Conditional Granger causality is needed to determine if the connection from X to Z is real or mediated through Y by determining how well Z can be predicted by X with versus without the inclusion of Y.