Matching pursuit decomposition of MEG auditory evoked fields
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1
University of Warsaw, Poland
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2
Leibniz Institute for Neurobiology, Germany
Matching pursuit (MP) is an algorithm for adaptive approximation of signals in redundant time-frequency dictionaries, composed usually from Gabor functions, that is sines modulated by Gaussian envelopes [1]. The first illustration presents the decomposition of an average MEG evoked field (AEF, lower right panel), evoked by an auditory stimulus. Functions #1--#5, fitted to this signal in the first five iterations of MP, are plotted in red. Their sum (blue) is superimposed on the AEF in the lower left plot. The function fitted in the first iteration (#1) seems to represent the M100 component of the AEF; these results so far are reproducible across subjects.
MP decomposition of a signal can be also used to construct high-resolution estimates of it's time-frequency energy density, free of cross-terms. The next figure presents statistically significant changes of the time-frequency energy distribution relative to the baseline chosen from the pre-stimulus period. The subject's task was to classify the acoustic stimulus and communicate the classification by pressing a button on a response pad. The blue area marked “A” indicates beta and alpha desynchronization in the peri-movement time, “B” corresponds to the sensory evoked potential related to pressing of the button, region marked “C” is beta and alpha rebound.
Finally, there are several multivariate variants of the MP algorithm [2]. They can be used for joint decomposition of all the repetitions of AEF. This provides an insight into evolution of EF components across single evoked responses.
References
1. Matching Pursuit and Unification in EEG Analysis, P.J. Durka, Artech House 2007
2. Event-Related Desynchronization and Synchronization in MEG: Framework for Analysis and Illustrative Datasets Related to Discrimination of Frequency-Modulated Tones, J. Żygierewicz, C. Sielużycki, R. Koenig, P.J. Durka, Journal of Neuroscience Methods 168(1), pp.239-47, 2008.
Conference:
Neuroinformatics 2008, Stockholm, Sweden, 7 Sep - 9 Sep, 2008.
Presentation Type:
Poster Presentation
Topic:
Electrophysiology
Citation:
Goj
R,
Sieluzycki
C,
Zacharias
N,
Jörn
M,
Heil
P,
Zygierewicz
J and
König
R
(2008). Matching pursuit decomposition of MEG auditory evoked fields.
Front. Neuroinform.
Conference Abstract:
Neuroinformatics 2008.
doi: 10.3389/conf.neuro.11.2008.01.106
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Received:
28 Jul 2008;
Published Online:
28 Jul 2008.
*
Correspondence:
Roman Goj, University of Warsaw, Granz, Poland, roman.goj@gmail.com