title: Contralateral dominance of corticomuscular coherence for both sides of the tongue during human tongue protrusion: an MEG study.
abstract: Sophisticated tongue movements contribute to speech and mastication. These movements are regulated by communication between the bilateral cortex and each tongue side. The functional connection between the cortex and tongue was investigated using oscillatory interactions between whole-head magnetoencephalographic (MEG) signals and electromyographic (EMG) signals from both tongue sides during human tongue protrusion compared to thumb data. MEG-EMG coherence was observed at 14-36 Hz and 2-10 Hz over both hemispheres for each tongue side. EMG-EMG coherence between tongue sides was also detected at the same frequency bands. Thumb coherence was detected at 15-33 Hz over the contralateral hemisphere. Tongue coherence at 14-36 Hz was larger over the contralateral vs. ipsilateral hemisphere for both tongue sides. Tongue cortical sources were located in the lower part of the central sulcus and were anterior and inferior to the thumb areas, agreeing with the classical homunculus. Cross-correlogram analysis showed the MEG signal preceded the EMG signal. The cortex-tongue time lag was shorter than the cortex-thumb time lag. The cortex-muscle time lag decreased systematically with distance. These results suggest that during tongue protrusions, descending motor commands are modulated by bilateral cortical oscillations, and each tongue side is dominated by the contralateral hemisphere.
authors.affiliation: Department of Oral Physiology, Graduate School of Dental Medicine, Hokkaido University, Kita-ku, Sapporo 060-8586, Japan. Electronic address: maezawa@den.hokudai.ac.jp.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Maezawa
authors.affiliation: Human Brain Research Center, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Mima
authors.affiliation: Department of Systems Neuroscience, School of Medicine, Sapporo Medical University, Chuo-ku, Sapporo 060-8556, Japan.
authors.forename: Shogo
authors.initials: S
authors.lastname: Yazawa
authors.affiliation: Human Brain Research Center, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan.
authors.forename: Masao
authors.initials: M
authors.lastname: Matsuhashi
authors.affiliation: Department of Pediatrics, Graduate School of Medicine, Hokkaido University, Kita-ku, Sapporo 060-8638, Japan.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Shiraishi
authors.affiliation: Department of Oral Physiology, Graduate School of Dental Medicine, Hokkaido University, Kita-ku, Sapporo 060-8586, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Hirai
authors.affiliation: Department of Oral Physiology, Graduate School of Dental Medicine, Hokkaido University, Kita-ku, Sapporo 060-8586, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Funahashi
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods*; D004576:Electromyography / Q000379:methods*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D013933:Thumb / Q000502:physiology; D014059:Tongue / Q000502:physiology*; D055815:Young Adult
keywords: Hypoglossal motor nucleus; Isometric muscle contraction; Magnetoencephalography; Neural oscillation; Primary motor cortex