The saccadic spike potential in magnetoencephalography
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1
University Medical Center Hamburg-Eppendorf,, Germany
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2
University of Osnabrück, Germany
Studying the neurophysiological basis of natural human vision faces the problem of strong eye movement induced electrical artifacts. The saccadic spike potential (SP) generates an electrical artifact that closely resembles neurophysiological gamma band activity in the electroencephalogram (EEG). This artifact is particularly problematic, since its occurrence is modulated by cognitive demands, even if subjects are instructed to fixate. It is speculated that the SP artifact is less problematic in magnetoencephalography (MEG) but evidence is missing. Here, we characterized the SP artifact induced in MEG measurements. To this end, we simultaneously recorded EEG, MEG, eye traces, and the electrooculogram. We compared the SP in MEG for a broad range of saccade size and direction and contrasted it to the well-known SP artifact in EEG. We found a saccade amplitude and direction dependent, lateralized SP, which most prominently affects the gamma frequency range. The SP in MEG was highest at frontal and temporal sensors but did not contaminate parietal sensors as in EEG. We further showed, that the SP characteristics of large-scale saccades are comparable to miniature saccades. Using beamforming and current equivalent dipole models, we identified the sources of the SP in the extra ocular muscles. In summary, the SP artifact is a serious problem also in MEG experiments. Our results provide a detailed description of the SP artifact in MEG data that constitutes a basis for assessing potential misinterpretations. Furthermore, we suggest that an analysis in source space is a good possibility to separate the SP artifacts from neurophysiological signals.
Keywords:
brain oscillations,
Saccadic spike potentials
Conference:
XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011.
Presentation Type:
Poster Presentation
Topic:
Poster Sessions: Quantitative Analysis of EEG, MEG & Brain Oscillations
Citation:
Carl
C,
Açık
A,
König
P,
Engel
AK and
Hipp
JF
(2011). The saccadic spike potential in magnetoencephalography.
Conference Abstract:
XI International Conference on Cognitive Neuroscience (ICON XI).
doi: 10.3389/conf.fnhum.2011.207.00142
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Received:
17 Nov 2011;
Published Online:
28 Nov 2011.
*
Correspondence:
Dr. Christine Carl, University Medical Center Hamburg-Eppendorf,, Hamburg, Germany, ccarl@uke.de