Validation of head movement correction and spatiotemporal signal space separation in magnetoencephalography.
OBJECTIVE
Our aim was to assess the effectiveness and reliability of spatiotemporal signal space separation (tSSS) and movement correction (MC) in magnetoencephalography (MEG) recordings disturbed by head movements and magnetized material on the head.


METHODS
We recorded MEG from 20 healthy adults in stationary (reference) head position and during controlled head movements. Nearby magnetic interference sources were simulated by attaching magnetized particles on the subject's head. Auditory and somatosensory stimuli were presented. MC, tSSS and averaging were performed to obtain auditory (AEF) and somatosensory (SEF) evoked fields. Neuronal sources were modeled as equivalent current dipoles. MC was also validated by reconstructing signals generated by current dipoles in a phantom.


RESULTS
After MC, the AEF and SEF responses recorded during intermittent head movements were similar in amplitude to the reference recordings and differed by 5-7mm in source location. The tSSS method removed artifacts due to the attached magnetized particles but did not affect the reference data.


CONCLUSIONS
The methods are able to reliably recover MEG responses contaminated by movements and magnetic artifacts on the head.


CONCLUSIONS
The combination of tSSS and MC methods is especially useful in clinical measurements, where movements and magnetic disturbances are commonly present.
Elekta Oy, Helsinki, Finland.
Jukka
J
Nenonen
Jussi
J
Nurminen
Dubravko
D
Kičić
Rozaliya
R
Bikmullina
Pantelis
P
Lioumis
Veikko
V
Jousmäki
Samu
S
Taulu
Lauri
L
Parkkonen
Miikka
M
Putaala
Seppo
S
Kähkönen
D000328:Adult; D016477:Artifacts; D001931:Brain Mapping / Q000379:methods*; D005072:Evoked Potentials, Auditory / Q000502:physiology; D005073:Evoked Potentials, Somatosensory / Q000502:physiology; D005260:Female; D019416:Head Movements / Q000502:physiology*; D006801:Humans; D060328:Magnetic Phenomena; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D059906:Neuroimaging / Q000379:methods; D015203:Reproducibility of Results; D013028:Space Perception / Q000502:physiology*; D062211:Spatio-Temporal Analysis