Disentangling mechanisms of evoked EEG/MEG response generation: A critical view
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1
HU, Germany
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2
Charité-University Medicine Berlin, Germany
Evoked responses (ERs) are primary real-time measures of perceptual and cognitive activity in the human brain. Currently there is a continuing debate on which mechanisms contribute to the generation of ERs: First, in case of an "additive" mechanism stimuli evoke a response which is independent of the ongoing activity. The second mechanism is based on "phase resetting" where ongoing oscillations adjust their phase in response to the stimuli. Importantly, arguments supporting either of these two views are based mainly on macroscopic ERs recorded from the human scalp with EEG/MEG. Here, we use a modeling in order to show how the stimulus-driven phase reorganization of microscopic oscillations may affect the macroscopic measures derived from EEG/MEG. To this end, we simulated a large number of mutually coupled neuronal oscillators and analyzed the amplitude dynamics of the whole ensemble. We show that although at the microscopic level the external stimulation does not lead to a change in the mean level of activity (pure phase reset), the macroscopic response might be associated with a pronounced increase in both the single-trial amplitude and the average ER, which is usually taken as evidence for the additive model of ERs. Furthermore, we show that the magnitude of such amplitude increase is dependent on the pre-stimulus population synchrony and large pre-stimulus synchrony is not associated with amplitude increase in macroscopically measured activity in agreement with phase-reset model of ERs. In summary, we show that, unless the exact level of synchrony between the microscopic elements is known, the analysis of neuronal processes underlying evoked responses in EEG/MEG is inconclusive. Our analysis is applicable to a large body of experimental EEG/MEG research and provides a critical argument to the current discussion about the mechanisms of ER generation. Acknowledgments: DFG (SFB 618, B4) and Berlin Bernstein Center for Computational Neuroscience (C4).
Conference:
Biomag 2010 - 17th International Conference on Biomagnetism , Dubrovnik, Croatia, 28 Mar - 1 Apr, 2010.
Presentation Type:
Poster Presentation
Topic:
MEG Modeling
Citation:
Telenczuk
B,
Nikulin
V and
Curio
G
(2010). Disentangling mechanisms of evoked EEG/MEG response generation: A critical view.
Front. Neurosci.
Conference Abstract:
Biomag 2010 - 17th International Conference on Biomagnetism .
doi: 10.3389/conf.fnins.2010.06.00082
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Received:
22 Mar 2010;
Published Online:
22 Mar 2010.
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Correspondence:
Bartosz Telenczuk, HU, Berlin, Germany, b.telenczuk@biologie.hu-berlin.de