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

Abstract

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.

Result: 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.

Conclusion: 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.

Significance: The results suggest that CKC can be used for SM1 cortex identification and for studies of proprioception even in patients implanted with magnetic material.

Keywords: Artifacts; Corticokinematic coherence; Functional mapping; Human brain; Magnetoencephalography; Proprioception; Signal-space separation.