Abstract
Corticokinematic coherence (CKC) between magnetoencephalographic and movement signals using an accelerometer is useful for the functional localization of the primary sensorimotor cortex (SM1). However, it is difficult to determine the tongue CKC because an accelerometer yields excessive magnetic artifacts. Here, we introduce a novel approach for measuring the tongue CKC using a deep learning-assisted motion capture system with videography, and compare it with an accelerometer in a control task measuring finger movement. Twelve healthy volunteers performed rhythmical side-to-side tongue movements in the whole-head magnetoencephalographic system, which were simultaneously recorded using a video camera and examined using a deep learning-assisted motion capture system. In the control task, right finger CKC measurements were simultaneously evaluated via motion capture and an accelerometer. The right finger CKC with motion capture was significant at the movement frequency peaks or its harmonics over the contralateral hemisphere; the motion-captured CKC was 84.9% similar to that with the accelerometer. The tongue CKC was significant at the movement frequency peaks or its harmonics over both hemispheres. The CKC sources of the tongue were considerably lateral and inferior to those of the finger. Thus, the CKC with deep learning-assisted motion capture can evaluate the functional localization of the tongue SM1.
Highlights
Corticokinematic coherence (CKC) between magnetoencephalographic and movement signals using an accelerometer is useful for the functional localization of the primary sensorimotor cortex (SM1)
Previous studies have shown that the CKC mainly reflects the proprioceptive input into the SM111–13; this feature is comparable to the strongest deflections observed in the cortical movement evoked fields (MEFs) associated with voluntary finger movements[14,15,16]
The peak CKC of the tongue was observed over the left hemisphere (CKC value: 0.43) and right hemisphere (CKC value: 0.46) at 3.3 Hz, around the harmonic frequency band of tongue movements (Fig. 2A[1,2])
Summary
Corticokinematic coherence (CKC) between magnetoencephalographic and movement signals using an accelerometer is useful for the functional localization of the primary sensorimotor cortex (SM1). A recording time of at least 10 min was required to examine the cortical representation of the tongue regions using these approaches In these approaches, it is technically challenging to set the EMG electrodes on narrow and wet tongue regions because placing electrodes on the tongue could result in discomfort in the subjects, and there is a risk of swallowing the electrode. Motion capture has been performed by placing tracking markers on the target regions of the s ubject[17,18,19,20,21] Applying this approach to tongues present technical problems because tracking markers set on wet tongue regions can be displaced during tasks involving tongue movements. While setting objects on the tongue, it is important to reduce the risk of infections such as COVID-19 to the experimenter via the saliva
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