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Posted November 2011 by C. Michel

New publication:

published in: Brain, 2011;134: 2887-97

Electroencephalographic source imaging: a prospective study of 152 

operated epileptic patients. 

by: V. Brodbeck, L. Spinelli, AM Lascano , M Wissmeier , MI Vargas, S. Vulliemoz, C .Pollo, K. Schaller, CM Michel and M. Seeck. 

This study presents a cohort of 152 operated patients where electric source imaging (ESI) was applied as part of the pre-surgical work-up allowing a comparison with the results from other imaging methods. Patients with >1 year postoperative follow-up were studied prospectively. The sensitivity and specificity of each imaging method was defined by comparing the localization of the source maximum with the resected zone and surgical outcome. Electric source imaging had a sensitivity of 84% and a specificity of 88% if the electroencephalogram was recorded with a large number of electrodes (128-256 channels) and the individual magnetic resonance image was used as head model. These values compared favorably with those of structural magnetic resonance imaging (76% sensitivity, 53% specificity), positron emission tomography (69% sensitivity, 44% specificity) and ictal/interictal single-photon emission-computed tomography (58% sensitivity, 47% specificity). The sensitivity and specificity of electric source imaging decreased to 57% and 59%, respectively, with low number of electrodes (<32 channels) and a template head model. This study demonstrated the validity and clinical utility of electric source imaging in a large prospective study. Given the low cost and high flexibility of electroencephalographic systems even with high channel counts, we conclude that electric source imaging is a highly valuable tool in pre-surgical epilepsy evaluation.



Posted September 2011 by C. Michel

New publication:


Right Parietal Brain Activity Precedes Perceptual Alternation During Binocular Rivalry
    by Juliane Britz, Michael A. Pitts and Christoph M. Michel
    in:  Human Brain Mapping 2011; 32(9): 1432-42.
      
    Study selected for the cover 

    In this study we investigated perceptual reversals for intermittently presented stimuli during binocular rivalry and physical alternation while the ongoing EEG was recorded from 64 channels. EEG topographies immediately preceding stimulus-onset were analyzed and two topographies doubly dissociated perceptual reversals from non-reversals. The estimated intracranial generators associated with these topographies were stronger in right inferior parietal cortex and weaker bilaterally in the ventral stream before perceptual reversals. No such differences were found for physical alternation of the same stimuli. These results replicate and extend findings from a previous study with the Necker cube and suggest common neural mechanisms associated with perceptual reversals during binocular rivalry and ambiguous figure perception. For both types of multi-stable stimuli, the dorsal stream is more active preceding perceptual reversals. Activity in the ventral stream, however, differed for binocular rivalry compared to ambiguous figures. The results from the two studies suggest a causal role for the right inferior parietal cortex in generating perceptual reversals regardless of the type of multi-stable stimulus, while activity in the ventral stream appears to depend on the particular type of stimulus.


Posted June 2011 by C. Michel

New publication:

Functional Development of 

Large-Scale Sensorimotor Cortical

Networks in the Brain

    by Charles Quairiaux, Pierre Mégevand, 
    Jozsef Z. Kiss, and Christoph M. Michel
    in:  J Neurosci. 2011 Jun 29;31(26):9574-84.
    This paper studied the functional development of large-scale neuronal networks in the postnatal rat sensorimotor system. Using epicranial multielectrode grids that span most of the cortical surface and intracortical electrodes, we show that sensory evoked cortical responses continuously maturate throughout the first 3 weeks with the strongest developmental changes occurring in a very short time around postnatal day 13. In a narrow time window of ∼48 h, a new early, sharp surface-positive component emerges that coincides with subsequent propagation of activity to sensory and motor areas of both hemispheres. Our data show that this new component developing at the end of the second week corresponds principally to functional maturation of the supragranular cortical layers and appears to be crucial for the functional associations in the large-scale sensorimotor cortical network. It goes along with the onset of whisking behavior, as well as major synaptic and functional changes within the S1 cortex that are known to develop during this period.



New MRI compatible EEG systems installed     

posted Mai 2011 by C. Michel


             

The functional brain mapping lab is proud to announce the installation of two 256-channel EEG systems that can be used for simultaneous EEG-fMRI studies.

The systems are from Electrical Geodesics Inc. (EGI, http://www.egi.com/). Both systems are combined with 3Tesla MRI systems from Siemens, one at the University Hospital for clinical studies http://epilepsie.hug-ge.ch/, the other at the University Medical Center for cognitive studies http://bbl.unige.ch/.

The systems are based on the HydroCel Geodesic Sensor Net technology that allow a very fast application of the 256 electrodes without using any paste and without skin abrasion.

The new systems will facilitate the use of high density EEG in the MRI and will thus increase the spatial resolution of the EEG recorded in the scanner and the precision of electrical neuroimaging techniques applied to the EEG data.

Several clinical and experimental studies by our group in collaboration with other centers have demonstrated the usefulness of a spatial analysis of the EEG in the scanner and a direct comparison with the fMRI:

Experimental studies:

Van de Ville D., Britz J, Michel CM. EEG microstate sequences in healthy humans at rest reveal scale-free dynamics. Proc Natl Acad Sci U S A, 2010; 107: 18179-18184.

Britz J, Van De Ville, D, Michel CM. BOLD correlates of EEG topography reveal rapid resting-state network dynamics. Neuroimage, 2010, 52:1162-70.

 Clinical studies:

Vulliemoz S, Rodionov R, Carmichael DW, Thornton R, Guye M, Lhatoo SD, Michel CM, Duncan JS, Lemieux L. Continuous EEG source imaging enhances analysis of EEG-fMRI in focal epilepsy. Neuroimage, 2010; 49: 3219-3229.

Vulliemoz S, Thornton R, Rodionov R, Carmichael DW, Guye M, Lhatoo S, McEvoy AW, Spinelli L, Michel CM, Duncan JS, Lemieux L. The spatio-temporal mapping of epileptic networks: combination of EEG-fMRI and EEG source imaging. Neuroimage. 2009; 46: 834-843.

Siniatchkin, M., Groening, K., Moehring, J., Moeller, F., Boor, R., Brodbeck, V., Michel, CM., Rodionov, R., Lemieux, L., Stephani, U. Neuronal networks in children with continuous spikes and waves during slow sleep. Brain, 133: 2798-2813.

Rodionov R, Siniatchkin M, Michel CM, Liston, AD, Thornton R, Guye M, Carmichael DW, Lemieux L. Looking for neuronal currents using MRI: an EEG-fMRI investigation of fast MR signal changes time-locked to frequent focal epileptic discharges. Neuroimage, 2010; 50:1109-1117.

Groening K, Brodbeck V, Moeller F, Wolff S, van Baalen A, Michel CM, Jansen O, Boor R, Wiegand G, Stephani U, Siniatchkin M. Combination of EEG-fMRI and EEG source analysis improves interpretation of spike-associated activation networks in paediatric pharmacoresistant focal epilepsies. Neuroimage, 2009; 46: 827-833.

Reviews:

Michel CM, Brandeis D. The sources and temporal dynamics of scalp electric fields. In: Ullsperger, S. Debener (Eds.) Simultaneous EEG and fMRI: Recording, Analysis, and Application, Oxford University Press, 2010, pp. 3-20.

Vulliemoz S, Lemieux L, Daunizeau J, Michel CM, Duncan JS. The combination of EEG Source Imaging and EEG-correlated functional MRI to map epileptic networks. Epilepsia, 2010; 51:491-505.


CARTOOL: The complete reference

posted March 2011 by C. Michel

Cartool, programmed by Denis BRUNET is an academic software package for the spatio-temporal analysis of EEG. It is freely available on this site. The main features of the software are now described in a paper published in a special issue of the journal "Computational Intelligence and Neuroscience". This special issue, edited by Sylvain Baillet, Karl Friston, and Robert Oostenveld is entitled "Academic Software Applications for Electromagnetic Brain Mapping Using MEG and EEG". It will contain several papers describing different software packages.

The paper on Cartool is written by Denis Brunet, Micah M. Murray, and Christoph M. Michel and is entitled:

Spatiotemporal Analysis of Multichannel EEG: CARTOOL

You may directly access the article at the following location:

http://www.hindawi.com/journals/cin/2011/813870.html

Please cite the article as follows:

Brunet, D., Murray M.M., Michel C.M. Spatiotemporal Analysis of Multichannel EEG: CARTOOL. Computational Intelligence and Neuroscience, Volume 2011 (2011).

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EEG-defined functional microstates as building blocks of consciousness

posted Jan 7, 2011 6:39 AM by Denis Brunet

Spontaneous EEG is characterized by a few prototypical maps that fluctuate over time as a sequence of quasi-stable epochs of around 100 ms duration. Already 30 years ago, Dietrich Lehmann proposed that these stable electric microstastates represent the basic building blocks of content of consciousness. Using combined EEG-fMRI we could now show that these EEG microstates correlate with some of the well-known fMRI resting states. Moreover, we could demonstrate that the EEG microstate sequence shows scale-free, monofractal temporal dynamics. We propose that this this scale-free dynamics of might be the basis for the rapid reorganization and adaptation of the functional networks of the brain that is required for conscious mental activities.

To read more:

Van de Ville D., Britz J, Michel CM. EEG microstate sequences in healthy humans at rest reveal scale-free dynamics. Proc Natl Acad Sci U S A, 2010; 107: 18179-18184.

Britz J, Van De Ville, D, Michel CM. BOLD correlates of EEG topography reveal rapid resting-state network dynamics. Neuroimage, 2010, 52:1162-1170.

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