Evaluating causal relations in neural systems: Granger causality, directedtransfer function and statistical assessment of significance

We consider the question of evaluating causal relations among neurobiologic al signals. In particular, we study the relation between the directed trans fer function (DTF) and the well-accepted Granger causality, and show that D TF can be interpreted within the framework of Granger causality. In additio n, we propose a method to assess the significance of causality measures. Fi nally, we demonstrate the applications of these measures to simulated data and actual neurobiological recordings.