Event-related desynchronization and synchronization in MEG: Framework for analysis and illustrative datasets related to discrimination of frequency-modulated tones.
We introduce a complete framework for the calculation of statistically significant event-related desynchronization and synchronization (ERD/ERS) in the time-frequency plane for magnetoencephalographic (MEG) data, and provide free Internet access to software and illustrative datasets related to a classification task of frequency-modulated (FM) tones. Event-related changes in MEG were analysed on the basis of the normal component of the magnetic field acquired by the 148 magnetometers of the hardware configuration of our whole-head MEG device, and by computing planar gradients in longitudinal and latitudinal direction. Time-frequency energy density for the magnetometer as well as the two gradient configurations is first approximated using short-time Fourier transform. Subsequently, detailed information is obtained from high-resolution time-frequency maps for the most interesting sensors by means of the computationally much more demanding matching pursuit parametrization. We argue that the ERD/ERS maps are easier to interpret in the gradient approaches and discuss the superior resolution of the matching pursuit time-frequency representation compared to short-time Fourier and wavelet transforms. Experimental results are accompanied by the following resources, available from http://brain.fuw.edu.pl/MEG: (a) 48 high-resolution figures presenting the results of four subjects in all applicable settings, (b) raw datasets, and (c) complete software environment, allowing to recompute these figures from the raw datasets.
Zygierewicz
J
J
Department of Biomedical Physics, Institute of Experimental Physics, Warsaw University, ul. Hoza 69, 00-681 Warszawa, Poland. jarekz@fuw.edu.pl <jarekz@fuw.edu.pl>
Sieluzycki
C
C
König
R
R
Durka
P J
PJ
D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D003344:Cortical Synchronization / Q000379:methods*; D016208:Databases, Factual; D004192:Discrimination, Psychological / Q000502:physiology*; D005072:Evoked Potentials, Auditory; D006801:Humans; D015225:Magnetoencephalography