Repetitive Passive Finger Movement Modulates Primary Somatosensory Cortex Excitability.

Ryoki Sasaki,Naofumi Otsuru,Shota Miyaguchi,Kei Saito,Sho Kojima,Yasuto Inukai,Hideaki Onishi,Shota Tsuiki

doi:10.3389/fnhum.2018.00332

Ryoki Sasaki, Naofumi Otsuru + Show 6 more

Open Access

https://doi.org/10.3389/fnhum.2018.00332

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Abstract

Somatosensory inputs induced by repetitive passive movement (RPM) modulate primary motor cortex (M1) excitability; however, it is unclear whether RPM affects primary somatosensory cortex (S1) excitability. In this study, we investigated whether RPM affects somatosensory evoked potentials (SEPs) and resting state brain oscillation, including alpha and beta bands, depend on RPM frequency. Nineteen healthy subjects participated in this study, and SEPs elicited by peripheral nerve electrical stimulation were recorded from the C3’ area in order to assess S1 excitability (Exp. 1: n = 15). We focused on prominent SEP components such as N20, P25 and P45-reflecting S1 activities. In addition, resting electroencephalograms (EEGs) were recorded from C3’ area to assess the internal state of the brain network at rest (Exp. 2: n = 15). Passive abduction/adduction of the right index finger was applied for 10 min at frequencies of 0.5, 1.0, 3.0, and 5.0 Hz in Exp. 1, and 1.0, 3.0, and 5.0 Hz in Exp. 2. No changes in N20 or P25 components were observed following RPM. The 3.0 Hz-RPM decreased the P45 component for 20 min (p < 0.05), but otherwise did not affect the P45 component. There was no difference in the alpha and beta bands before and after any RPM; however, a negative correlation was observed between the rate of change of beta power and P45 component at 3.0 Hz-RPM. Our findings indicated that the P45 component changes depending on the RPM frequency, suggesting that somatosensory inputs induced by RPM influences S1 excitability. Additionally, beta power enhancement appears to contribute to the P45 component depression in 3.0 Hz-RPM.

Highlights

Various types of repetitive somatosensory inputs are capable of evoking neuroplastic changes in the primary motor cortex (M1)
We showed that motor-evoked potentials (MEPs) decreased immediately after 0.5 Hz- and 1.0 Hz-repetitive passive movement (RPM), while 5.0 Hz-RPM induced a decrease that lasted for 15 min
This study investigated whether RPMs affect somatosensory evoked potentials (SEPs) and resting EEG, including alpha and beta bands, depending on movement frequency

Summary

Introduction

Various types of repetitive somatosensory inputs are capable of evoking neuroplastic changes in the primary motor cortex (M1). Previous studies have reported changes in motor-evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) over the M1 after a prolonged period of peripheral nerve electrical stimulation (Ridding et al, 2000; Kaelin-Lang et al, 2002; Sasaki et al, 2017a). Muscle vibration or water flow stimulation has been shown to modulate MEPs (Steyvers et al, 2003; Sato et al, 2015). These MEP changes induced by repetitive somatosensory inputs are believed to occur at the level of the cortex, because neither H-reflex nor F-wave amplitude, which selectively reflects spinal motoneuron excitability, differs following. RPMs may contribute to a rehabilitation approach in order to induce neuroplastic change in M1; the M1 excitability depression mechanism induced by RPM remains unclear

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