Reliable recording and analysis of MEG-based corticokinematic coherence in the presence of strong magnetic artifacts.
OBJECTIVE
Corticokinematic coherence (CKC) is the coupling between magnetoencephalographic (MEG) signals and limb kinematics during fast movements. Our objective was to assess the robustness of CKC-based identification of the primary sensorimotor (SM1) cortex of subjects producing strong magnetic artifacts when the MEG signals were cleaned with temporal signal space separation (tSSS).


METHODS
We recorded MEG during active and passive forefinger movements and during median-nerve stimulation in the following conditions: (1) artifact-free, (2) a magnetic wire attached to the scalp at C3 location, and (3) a magnetic wire attached behind the lower central incisors. Data were pre-processed with tSSS and analyzed using standard CKC methods, somatosensory evoked fields (SEFs), and dipole modeling.


RESULTS
Artifacts were effectively suppressed by tSSS, enabling successful identification of the SM1 cortex in all subjects based on CKC and SEFs. The sources were in artifact conditions ∼5 mm away from the sources identified in artifact-free conditions.


CONCLUSIONS
tSSS suppressed artifacts strongly enough to enable reliable identification of the SM1 cortex on the basis of CKC mapping, with localization accuracy comparable to SEF-based mapping.


CONCLUSIONS
The results suggest that CKC can be used for SM1 cortex identification and for studies of proprioception even in patients implanted with magnetic material.
Brain Research Unit, Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, PO Box 15100, FI-00076 Aalto, Espoo, Finland. Electronic address: mathieu.bourguignon@aalto.fi.
Mathieu
M
Bourguignon
NatMEG, Department of Clinical Neuroscience, Karolinska Institutet, Nobels väg 9, 171 77 Stockholm, Sweden.
Stephen
S
Whitmarsh
Brain Research Unit, Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, PO Box 15100, FI-00076 Aalto, Espoo, Finland.
Harri
H
Piitulainen
Brain Research Unit, Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, PO Box 15100, FI-00076 Aalto, Espoo, Finland.
Riitta
R
Hari
Brain Research Unit, Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, PO Box 15100, FI-00076 Aalto, Espoo, Finland.
Veikko
V
Jousmäki
NatMEG, Department of Clinical Neuroscience, Karolinska Institutet, Nobels väg 9, 171 77 Stockholm, Sweden.
Daniel
D
Lundqvist
D000328:Adult; D016477:Artifacts; D001696:Biomechanical Phenomena / Q000502:physiology; D004558:Electric Stimulation / Q000379:methods; D005073:Evoked Potentials, Somatosensory / Q000502:physiology; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods / Q000592:standards*; D059346:Magnets / Q000009:adverse effects*; D008297:Male; D008475:Median Nerve / Q000502:physiology; D008875:Middle Aged; D009068:Movement / Q000502:physiology; D013003:Somatosensory Cortex / Q000502:physiology*
Artifacts; Corticokinematic coherence; Functional mapping; Human brain; Magnetoencephalography; Proprioception; Signal-space separation