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Stepping stone sampling for retrieving artifact-free electroencephalogram during functional magnetic resonance
Kimitaka Anami1, Takeyuki Mori, Fumiko Tanaka
1Department of Psychiatry, National Center Hospital for Mental, Nervous, and Muscular Disorders, National Center of Neurology and Psychiatry, Tokyo 187-8551, Japan. anami@ncnpmusashi.gr.jp
Neuroimage
|June 20, 2003
Summary
Researchers developed "stepping stone sampling" to overcome interference from ballistocardiogram and imaging artifacts during simultaneous electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) recordings. This method successfully retrieves EEG signals, even in the gamma band, during fMRI acquisition.
Area of Science:
- Neuroscience
- Biomedical Engineering
- Signal Processing
Background:
- Simultaneous electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) offer complementary insights into brain activity.
- Ballistocardiogram and fMRI-induced artifacts severely contaminate EEG signals, hindering data analysis.
- Existing methods struggle to effectively remove these large-amplitude artifacts, limiting the retrieval of high-fidelity EEG data.
Purpose of the Study:
- To develop a novel method for artifact reduction to enable high-quality simultaneous EEG-fMRI recording.
- To characterize the waveform of fMRI imaging artifacts for targeted signal processing.
- To validate the efficacy of the new method in retrieving clean EEG signals, including high-frequency components.
Main Methods:
- High-sampling rate (20,000 Hz) recording and low-pass filtering (3000 Hz) to analyze artifact waveforms.
- Modification of a blip-type echo planar sequence for targeted EEG sampling during artifact-free periods (1000 Hz digitization rate).
- Implementation of "stepping stone sampling" combined with artifact waveform subtraction for signal retrieval.
Main Results:
- The study elucidated that fMRI artifact peaks correspond to gradient components with distinct waveforms.
- "Stepping stone sampling" significantly reduced artifact amplitude during EEG acquisition.
- Retrieved EEG data showed high similarity in power distribution (DC to 120 Hz) to non-fMRI data, including gamma band activity.
- Successful retrieval of alpha activity, with observable changes during eyes-open/closed conditions, was demonstrated.
Conclusions:
- "Stepping stone sampling" is an effective technique for mitigating fMRI artifacts in simultaneous EEG recordings.
- The method allows for the retrieval of high-quality EEG signals across a wide frequency range, including gamma band.
- This advancement facilitates more robust and comprehensive neuroimaging research combining EEG and fMRI.