Reliable recording and analysis of MEG-based corticokinematic coherence in the presence of strong magnetic artifacts

- MEG-based corticokinematic coherence (CKC) reliably locates the primary sensorimotor (SM1) cortex.
- In subjects wearing magnetized material, temporal signal-space separation effectively cleans the MEG data.
- In the presence of such artifacts, CKC still locates the SM1 cortex with ∼5 mm accuracy and allows reliable studies of proprioception.

ObjectiveCorticokinematic 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).MethodsWe 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.ResultArtifacts 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.ConclusiontSSS 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.SignificanceThe results suggest that CKC can be used for SM1 cortex identification and for studies of proprioception even in patients implanted with magnetic material.