Transcranial static magnetic field stimulation - new non-invasive brain stimulation tool

Abstract

Recent research has shown that the human motor cortex can be modulated by the application of static magnetic fields through the scalp. Transcranial static magnetic field stimulation (tSMS) has since received significant attention as a new non-invasive brain stimulation (NIBS) technique alongside conventional methods, such as repetitive transcranial magnetic stimulation and transcranial direct current stimulation. The advantages of the strong neodymium, iron and boron (NdFeB) magnet used in tSMS over other NIBS methods include the ease of use, absence of uncomfortable sensations for subjects, a lack of necessity for high operational skills and expensive devices, and conclusive sham stimulation allowing for controlled experiments and randomized controlled clinical trials. Hence, tSMS may be a new potential NIBS tool to modulate cerebral excitability.

Static magnetic field stimulation applied over the cervical spinal cord can decrease corticospinal excitability in finger muscle

“…It is well known that the intensity of a static magnetic field dramatically decreases with increasing distance from the magnet ( Paulus, 2011 , Rivadulla et al, 2014 , Kirimoto et al, 2016b ). For example, the intensity of the magnet axis was approximately 0.48 Tesla at the magnet surface (distance 0 cm), whereas it would drop to 0.15 Tesla at a distance of 2 cm ( Paulus, 2011 ).…”

“…Thus, the present study may be the first human study to show that neural excitability can be modulated even at a distance of 4–5 cm. At this distance, a static magnetic field of around 50 mTesla would likely act on the spinal cord ( Kirimoto et al, 2016a , Kirimoto et al, 2016b ). Although that is much weaker than normally used in human cortical studies, many animal or in vitro studies have confirmed that such weak static magnetic fields can alter neural excitability or function ( Kholodov, 1974 , Ben Yakir-Blumkin et al, 2014 ).…”

“…The duration of the magnet or sham stimulation was 15 min, and the subjects were asked to relax during the intervention and TMS measurements. The 15 min duration was chosen as the median value of the durations used in previous tSMS studies, which ranged from 10 to 20 min (10 min: Gonzalez-Rosa et al, 2015, 15 min: Kirimoto et al, 2014 , Kirimoto et al, 2016a , Kirimoto et al, 2016b , 20 min: Oliviero et al, 2011 , Nojima et al, 2015 ).

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“…Local applications of static magnetic fields to the human cortex modulates cortical excitability ( Oliviero et al, 2011 , Kirimoto et al, 2014 , Gonzalez-Rosa et al, 2015 , Nojima et al, 2015 , Kirimoto et al, 2016a , Kirimoto et al, 2016b , Nojima et al, 2016 ). Oliviero et al (2011) were the first to report that transcranial static magnetic field stimulation (tSMS) using small, strong magnets over the human motor cortex decreased excitability of the motor cortex.…”

Accuracy in Pinch Force Control Can Be Altered by Static Magnetic Field Stimulation Over the Primary Motor Cortex

“…The objective of this study was to investigate whether tSMS over M1 can alter voluntary ballistic force control, and if so, how this occurs. Because only the suppression effects of tSMS on neural excitability have previously been shown , it is possible that motor commands required to reach a predetermined force level decay through tSMS‐affected M1. In this case, tSMS of M1 could weaken voluntary force output.…”