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Computational Intelligence and Neuroscience
Volume 2011 (2011), Article ID 938925, 14 pages
Research Article

Ragu: A Free Tool for the Analysis of EEG and MEG Event-Related Scalp Field Data Using Global Randomization Statistics

1Department of Psychiatric Neurophysiology, University Hospital of Psychiatry Bern, University of Bern, 3000 Bern 60, Bolligenstr. 111, Switzerland
2Neuroinformatics Department, Cuban Neuroscience Center, Havana 15202, Cuba

Received 30 September 2010; Revised 7 December 2010; Accepted 31 December 2010

Academic Editor: Sylvain Baillet

Copyright © 2011 Thomas Koenig et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We present a program (Ragu; Randomization Graphical User interface) for statistical analyses of multichannel event-related EEG and MEG experiments. Based on measures of scalp field differences including all sensors, and using powerful, assumption-free randomization statistics, the program yields robust, physiologically meaningful conclusions based on the entire, untransformed, and unbiased set of measurements. Ragu accommodates up to two within-subject factors and one between-subject factor with multiple levels each. Significance is computed as function of time and can be controlled for type II errors with overall analyses. Results are displayed in an intuitive visual interface that allows further exploration of the findings. A sample analysis of an ERP experiment illustrates the different possibilities offered by Ragu. The aim of Ragu is to maximize statistical power while minimizing the need for a-priori choices of models and parameters (like inverse models or sensors of interest) that interact with and bias statistics.