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AuthorSpencer G.S.
AuthorSmith J.A.
AuthorChowdhury M.E.H.
AuthorBowtell R.
AuthorMullinger K.J.
Available date2019-09-30T07:47:43Z
Publication Date2018
Publication NameNeuroImage
ResourceScopus
ISSN1053-8119
URIhttp://dx.doi.org/10.1016/j.neuroimage.2018.02.034
URIhttp://hdl.handle.net/10576/11975
AbstractMotion artefacts (MAs) are induced within EEG data collected simultaneously with fMRI when the subject's head rotates relative to the magnetic field. The effects of these artefacts have generally been ameliorated by removing periods of data during which large artefact voltages appear in the EEG traces. However, even when combined with other standard post-processing methods, this strategy does not remove smaller MAs which can dominate the neuronal signals of interest. A number of methods are therefore being developed to characterise the MA by measuring reference signals and then using these in artefact correction. These methods generally assume that the head and EEG cap, plus any attached sensors, form a rigid body which can be characterised by a standard set of six motion parameters. Here we investigate the motion of the head/EEG cap system to provide a better understanding of MAs. We focus on the reference layer artefact subtraction (RLAS) approach, as this allows measurement of a separate reference signal for each electrode that is being used to measure brain activity. Through a series of experiments on phantoms and subjects, we find that movement of the EEG cap relative to the phantom and skin on the forehead is relatively small and that this non-rigid body movement does not appear to cause considerable discrepancy in artefacts between the scalp and reference signals. However, differences in the amplitude of these signals is observed which may be due to differences in geometry of the system from which the reference signals are measured compared with the brain signals. In addition, we find that there is non-rigid body movement of the skull and skin which produces an additional MA component for a head shake, which is not present for a head nod. This results in a large discrepancy in the amplitude and temporal profile of the MA measured on the scalp and reference layer, reducing the efficacy of MA correction based on the reference signals. Together our data suggest that the efficacy of the correction of MA using any reference-based system is likely to differ for different types of head movement with head shake being the hardest to correct. This provides new information to inform the development of hardware and post-processing methods for removing MAs from EEG data acquired simultaneously with fMRI data. 2018
SponsorThis work was funded by an MRC Confidence in Concept Award MC_PC_15033 , awarded through the University of Nottingham . This work was carried out using the facilities of the Sir Peter Mansfield Imaging Centre (SPMIC). The establishment of the SPMIC was funded by MRC grant MR/M009122/1 . The Centre's facilities have also been funded by EPSRC , HEFCE , Wellcome and the University of Nottingham . Appendix A
Languageen
PublisherAcademic Press Inc.
SubjectArtefact correction
Motion artefacts
Motion characterisation
Simultaneous EEG-fMRI
TitleExploring the origins of EEG motion artefacts during simultaneous fMRI acquisition: Implications for motion artefact correction
TypeArticle
Pagination188-198
Volume Number173
dc.accessType Open Access


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