Research

Brain connectivity measures: computation and comparison

¹⁴ Faculty of Mathematics, University of Belgrade, Group For Intelligent Systems Studentski Trg 16, 11000, Belgrade, Serbia
¹⁵ Faculty of Transportation and Traffic Engineering, University of Belgrade, Vojvode Stepe 305, 11000, Belgrade, Serbia

^* e-mail: aljosha.jovanovich@gmail.com

Received: 1 January 2013
Accepted: 9 May 2013
Published online: 9 May 2013

Abstract

In this article computation and comparison of causality measures which are used in determination of brain connectivity patterns is investigated. Main analyzed examples included published computation and comparisons of Directed Transfer Function ‐ DTF and Partial Directed Coherence ‐ PDC. It proved that serious methodology mistakes were involved in measure computations and comparisons. It is shown that the neighborhood of zero is of accented importance in such evaluations and that the issues of semantic stability have to be treated with more attention. Published results on the relationship of these two important measures are partly unstable with small changes of zero threshold and pictures of involved brain structures deduced from the cited articles have to be corrected. Analysis of the operators involved in evaluation and comparisons is given with suggestions for their improvement and complementary additional actions.