Modulation of sensorimotor cortex by repetitive peripheral magnetic stimulation

Abstract

This study examines with transcranial magnetic stimulation (TMS) and with functional magnetic resonance imaging (fMRI) whether 20 min of repetitive peripheral magnetic stimulation (rPMS) has a facilitating effect on associated motor controlling regions. Trains of rPMS with a stimulus intensity of 150% of the motor threshold (MT) were applied over right hand flexor muscles of healthy volunteers. First, with TMS, 10 vs. 25 Hz rPMS was examined and compared to a control group. Single and paired pulse motor evoked potentials (MEPs) from flexor carpi radialis (FCR) and extensor carpi radialis (ECR) muscles were recorded at baseline (T0), post rPMS (T1), 30 min post (T2), 1 h post (T3) and 2 h post rPMS (T4). Then, with fMRI, 25 Hz rPMS was compared to sham stimulation by utilizing a finger tapping activation paradigm. Changes in bloodoxygen level dependent (BOLD) contrast were examined at baseline (PRE), post rPMS (POST1) and 1 h post rPMS (POST2). With TMS facilitation was observed in the target muscle (FCR) following 25 Hz rPMS: MEP recruitment curves (RCs) were increased at T1, T2 and T3, and intracortical facilitation (ICF) was increased at T1 and T2. No effects were observed following 10 Hz rPMS. With fMRI the BOLD contrast at the left sensorimotor area was increased at POST1. Compared to inductions protocols based on transcutaneous electrical stimulation and mechanical stimulation, the rPMS induced effects appeared shorter lasting.

Coupling Magnetically Induced Electric Fields to Neurons: Longitudinal and Transverse Activation

“…TMS is approved by the United States of America Food and Drug Administration for the treatment of depression and migraine, as well as for presurgical cortical mapping, and is under study for other neurological and psychiatric disorders (2,3). Magnetic stimulation of peripheral nerves, which is also cleared by the Food and Drug Administration, is used for nerve conduction testing, neuromodulation, and neurorehabilitation (4)(5)(6)(7). The mechanisms determining the neural response to magnetic stimulation are still unclear, and experimental studies rely heavily on indirect, noninvasive measurements such as brain imaging and downstream neuromuscular responses (8,9).…”

Coupling magnetically induced electric fields to neurons: longitudinal and transverse activation

“…TMS is approved by the U.S.A. Food and Drug Administration (FDA) for the treatment of depression and migraine, as well as for pre-surgical cortical mapping, and is under study for other neurological and psychiatric disorders (2,3). Magnetic stimulation of peripheral nerves, which is also FDA cleared, is used for nerve conduction testing, neuromodulation, and neurorehabilitation (4)(5)(6)(7). The mechanisms determining the neural response to magnetic stimulation are still unclear, and experimental studies rely heavily on indirect, non-invasive measurements such as brain imaging and downstream neuromuscular responses (8,9).…”

Modulation of motor cortex excitability by paired peripheral and transcranial magnetic stimulation

“…Suprathreshold, 20 Hz rPMS (2000 pulses in a single session) applied over cervical roots (C7/C8) led to prolongation of the CSP (Krause et al 2005, Krause andStraube 2008), increase amplitude of MEP and raised SICI (Krause and Straube 2008). However, the facilitation of corticospinal and intracortical excitability induced by rPMS is sensitive to the frequency and the total number of applied magnetic impulses with higher frequency and greater number of stimuli inducing more robust effects (Gallasch et al 2015).…”

“…Because the baseline SICI seems to be a determining factor of the modulatory effects of PAS (Murase et al 2015, Russmann et al 2009 future studies should evaluate the effects of GABA-ergic medication on motor cortex plasticity related with magnetic-PAS. The neuromodulatory effects of rPMS are sensitive to the frequency and the total number of applied stimuli (Gallasch et al 2015, Krause et al 2005, Krause and Straube 2008 therefore future research studies should also investigate whether employing higher frequencies and larger durations of rPMS in magnetic-PAS protocols could enhance M1 cortex facilitation.…”