More comprehensive proprioceptive stimulation of the hand amplifies its cortical processing

Corticokinematic coherence (CKC) quantifies the phase coupling between limb kinematics and cortical neurophysiological signals reflecting proprioceptive feedback to the primary sensorimotor (SM1) cortex. We studied CKC to proprioceptive stimulation (i.e. movement-actuator-evoked movements) of right-hand digits (index, middle, ring and little) performed simultaneously or separately. CKC was computed between magnetoencephalography (MEG) and finger acceleration signals. The strongest CKC was obtained by stimulating the fingers simultaneously at fixed 3-Hz frequency, and can, therefore, be recommended as design for fast functional localization of the hand area in the primary sensorimotor (SM1) cortex using MEG. The peaks of CKC sources were concentrated in the hand region of the SM1 cortex, but did not follow consistent somatotopic order. This result suggests that spatial specificity of MEG is not sufficient to separate proprioceptive finger representations of the same hand adequately or that their representations are overlapping.