Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6023587 | NeuroImage | 2016 | 13 Pages |
â¢Motion causes spurious effects using common artifact correction in EEG-fMRI analysis.â¢Spurious motion effects resemble neurophysiological plausible effects.â¢Minor task-related motion can cause spurious task-related EEG effects.â¢Motion-BOLD and EEG-BOLD correlations are largely overlapping after convolution with the HRF.
Simultaneous EEG-fMRI provides an increasingly attractive research tool to investigate cognitive processes with high temporal and spatial resolution. However, artifacts in EEG data introduced by the MR scanner still remain a major obstacle. This study, employing commonly used artifact correction steps, shows that head motion, one overlooked major source of artifacts in EEG-fMRI data, can cause plausible EEG effects and EEG-BOLD correlations. Specifically, low-frequency EEG (<Â 20Â Hz) is strongly correlated with in-scanner movement. Accordingly, minor head motion (<Â 0.2Â mm) induces spurious effects in a twofold manner: Small differences in task-correlated motion elicit spurious low-frequency effects, and, as motion concurrently influences fMRI data, EEG-BOLD correlations closely match motion-fMRI correlations. We demonstrate these effects in a memory encoding experiment showing that obtained theta power (~Â 3-7Â Hz) effects and channel-level theta-BOLD correlations reflect motion in the scanner. These findings highlight an important caveat that needs to be addressed by future EEG-fMRI studies.