Narrow Results

An extension of transfer entropy, called partial transfer entropy (PTE), is proposed to detect causal effects among observed interacting systems, and particularly to distinguish direct from indirect causal effects. PTE is compared to a linear direct causality measure, the Partial Directed Coherence (PDC), on known linear stochastic systems and nonlinear deterministic systems. PTE performs equally well as PDC on the linear systems and better than PDC on the nonlinear systems, both being dependent on the selection of the measure specific parameters. PTE and PDC are applied to electroencephalograms of epileptic patients during the preictal, ictal and postictal states, and PTE turns out to detect better changes of the strength of the direct causality at specific pairs of electrodes and for the different states.