Transcranial Static Magnetic Field Stimulation Research Articles

TMS-EEG signatures of the effects of transcranial static magnetic field stimulation (tSMS) on cortical excitability

In transcranial static magnetic field stimulation (tSMS), a strong and small magnet placed over the head can modulate cortical functions below the magnet as well as those in the region remote from the magnet. We studied the neuromodulation induced by tSMS using transcranial magnetic stimulation (TMS) combined with simultaneous electroencephalography (EEG) to clarify the neurophysiological underpinnings of tSMS. tSMS or sham stimulation was applied over the left primary motor cortex (M1) for 20 min in 15 healthy subjects. Single pulse TMS was delivered over the left M1 before and after the intervention, while recording EEG. The amplitude around the P30 of the TMS-evoked potentials (TEPs) in the left primary sensorimotor area (SM1) significantly decreased after the real tSMS, and that around the N60 of the TEPs in the right SM1 significantly increased after the real tSMS. In addition, the alpha power of the TMS-induced oscillatory responses (IORs) in the left and right SM1 significantly decreased after the real tSMS. TMS-EEG is a powerful tool for studying local and global cortical reactivity to external stimuli at high temporal resolution. tSMS altered TEPs and IORs both at the stimulated cortex and at the contralateral cortex. These findings would be related to the neurophysiological mechanisms underlying the neuromodulation induced by tSMS.

Transcranial static magnetic field stimulation of the supplementary motor area decreases corticospinal excitability in the motor cortex: a pilot study

Transcranial static magnetic field stimulation (tSMS) is a non-invasive brain stimulation technique that is portable and easy to use. Long-term, home-based treatments with tSMS of the supplementary motor area (SMA) are promising for movement disorders and other brain diseases. The aim of the present work was to investigate the potential of SMA-tSMS for reducing corticospinal excitability. We completed an open pilot study in which twenty right-handed healthy subjects (8 females; age: 31.3 ± 5.4 years) completed two 30-min sessions (at least one week apart) of SMA-tSMS. We assessed corticospinal excitability by applying transcranial magnetic stimulation (TMS) over the primary motor cortex, recording 30 motor evoked potentials (MEPs) from either the left or right first dorsal interosseous (FDI, ‘hotspot’ muscle) and extensor carpi radialis (ECR, ‘offspot’ muscle) in each session before and after (up to 30 min) tSMS. We observed moderate-to-extreme level of Bayesian evidence for a reduction of MEP amplitude after 30 min of tSMS over SMA compared to baseline. Thus, tSMS applied over SMA may reduce corticospinal excitability. These findings, if confirmed with double-blind, placebo-controlled experiments, support the potential of targeting the SMA for neuromodulating a large motor network in future therapeutic applications of tSMS.

Tackling social anxiety with targeted brain stimulation: investigating the effects of transcranial static magnetic field stimulation on self-focused attention.

Previous studies suggested that self-focused attention (SFA), implicated in social anxiety disorder (SAD), correlates with heightened activity in the right frontopolar area (rFPA), which is the right prefrontal cortex just behind the forehead. Transcranial static magnetic field stimulation (tSMS) is a non-invasive brain stimulation method capable of temporarily suppressing brain function beneath the magnet. We explored whether tSMS on individuals with tendencies toward SAD elicited (1) suppressing rFPA activation during the resting-state and (2) reducing SFA during a subsequent speech task. Twenty-three university students with social anxiety performed two speech tasks. Between tasks, the tSMS group received neodymium magnet stimulation while the sham group received fake magnet stimulation on the rFPA for 20 min. Resting-state rFPA activities was measured using functional near-infrared spectroscopy (fNIRS), while SFA (body sensations and observer perspective), field perspective, and detached mindfulness (DM) perspective were assessed via questionnaires during both speech tasks. The observer perspective means SFA to self-imagery from others' viewpoint, while the field and DM perspectives mean appropriately focusing on the external environment. The results indicated that tSMS intervention decreased rFPA activity from pre- to post-intervention rest. Then, tSMS reduced SFA to bodily sensations and increased DM perspective from pre- to post-intervention speech, especially in those with high levels of social anxiety. Furthermore, tSMS enhanced the field perspective regardless of social anxiety tendency. The results suggest that tSMS may suppress overactivity in rFPA, reduce SFA to body sensation, and increase adaptive attention in highly socially anxious individuals. Our study suggests the possibility of the clinical application of tSMS for treating SAD.

Static Magnetic Field Stimulation Enhances Shunting Inhibition via a SLC26 Family Cl- Channel, Inducing Intrinsic Plasticity.

Magnetic fields are being used for detailed anatomical and functional examination of the human brain. In addition, evidence for their efficacy in treatment of brain dysfunctions is accumulating. Transcranial static magnetic field stimulation (tSMS) is a recently developed technique for noninvasively modifying brain functions. In tSMS, a strong and small magnet when placed over the skull can temporarily suppress brain functions. Its modulatory effects persist beyond the time of stimulation. However, the neurophysiological mechanisms underlying tSMS-induced plasticity remain unclear. Here, using acute motor cortical slice preparation obtained from male C57BL/6N mice, we show that tSMS alters the intrinsic electrical properties of neurons by altering the activity of chloride (Cl-) channels in neurons. Exposure of mouse pyramidal neurons to a static magnetic field (SMF) at a strength similar to human tSMS temporarily decreased their excitability and induced transient neuronal swelling. The effects of SMF were blocked by DIDS and GlyH-101, but not by NPPB, consistent with the pharmacological profile of SLC26A11, a transporter protein with Cl- channel activity. Whole-cell voltage-clamp recordings of the GlyH-101-sensitive Cl- current component showed significant enhancement of the component at both subthreshold and depolarized membrane potentials after SMF application, resulting in shunting inhibition and reduced repetitive action potential (AP) firing at the respective potentials. Thus, this study provides the first neurophysiological evidence for the inhibitory effect of tSMS on neuronal activity and advances our mechanistic understanding of noninvasive human neuromodulation.

Transcranial static magnetic field stimulation over hMT+ inhibits visual motion discriminability

Visuomotor performance acting on a moving target is fundamentally based on visual motion discriminability, and its neural basis is presumed to be human MT (hMT+), a motion vision center of the dorsal visual pathway. In this study, we investigated whether and how the accuracy and speed of motion discrimination are affected by applying transcranial static magnetic field stimulation (tSMS) to hMT+, which reduces cortical excitability. Sixteen participants performed a motion direction discrimination (MDD) task using a random dot kinematogram before (Pre-test) and during (During-test) application of the tSMS over left hMT+. The correct rate of the MDD task was significantly lower in the During-test compared to the Pre-test, an effect not seen with the sham condition. The inhibition effects were observed only for the right visual field corresponding to hMT+ in the stimulated hemisphere. On the other hand, no modulatory effect of tSMS was observed in the reaction time. We, therefore, demonstrated the inhibitory effect of tSMS on the left hMT+ impairs the accuracy but not the speed of motion information processing in the contralateral visual field.

Noninvasive modulation of human corticostriatal activity

Corticostriatal activity is an appealing target for nonpharmacological treatments of brain disorders. In humans, corticostriatal activity may be modulated with noninvasive brain stimulation (NIBS). However, a NIBS protocol with a sound neuroimaging measure demonstrating a change in corticostriatal activity is currently lacking. Here, we combine transcranial static magnetic field stimulation (tSMS) with resting-state functional MRI (fMRI). We first present and validate the ISAAC analysis, a well-principled framework that disambiguates functional connectivity between regions from local activity within regions. All measures of the framework suggested that the region along the medial cortex displaying greater functional connectivity with the striatum is the supplementary motor area (SMA), where we applied tSMS. We then use a data-driven version of the framework to show that tSMS of the SMA modulates the local activity in the SMA proper, in the adjacent sensorimotor cortex, and in the motor striatum. We finally use a model-driven version of the framework to clarify that the tSMS-induced modulation of striatal activity can be primarily explained by a change in the shared activity between the modulated motor cortical areas and the motor striatum. These results suggest that corticostriatal activity can be targeted, monitored, and modulated noninvasively in humans.

The Supplementary Motor Area and Automatic Cognitive Control: Lack of Evidence from Two Neuromodulation Techniques.

The SMA is fundamental in planning voluntary movements and execution of some cognitive control operations. Specifically, the SMA has been known to play a dominant role in controlling goal-directed actions as well as those that are highly predicted (i.e., automatic). Yet, the essential contribution of SMA in goal-directed or automatic control of behavior is scarce. Our objective was to test the possible direct role of SMA in automatic and voluntary response inhibition. We separately applied two noninvasive brain stimulation (NIBS) inhibitory techniques over SMA: either continuous theta-burst stimulation using repetitive transcranial magnetic stimulation or transcranial static magnetic field stimulation. Each NIBS technique was performed in a randomized, crossover, sham-controlled design. Before applying NIBS, participants practiced a go/no-go learning task where associations between stimulus and stopping behaviors were created (initiation and inhibition). After applying each NIBS, participants performed a go/no-go task with reversed associations (automatic control) and the stop signal task (voluntary control). Learning associations between stimuli and response initiation/inhibition was achieved by participants and therefore automatized during training. However, no significant differences between real and sham NIBS were found in either automatic (go/no-go learning task) or voluntary inhibition (stop signal task), with Bayesian statistics providing moderate evidence of absence. In conclusion, our results are compatible with a nondirect involvement of SMA in automatic control of behavior. Further studies are needed to prove a noncausal link between prior neuroimaging findings relative to SMA controlling functions and the observed behavior.

Effects of transcranial static magnetic field stimulation over the left dorsolateral prefrontal cortex on random number generation

ObjectiveFocal application of transcranial static magnetic field stimulation (tSMS) is a neuromodulation technique, with predominantly inhibitory effects when applied to the motor, somatosensory or visual cortex. Whether this approach can also transiently interact with dorsolateral prefrontal cortex (DLPFC) function remains unclear. The suppression of habitual or competitive responses is one of the core executive functions linked to DLPFC function. This study aimed to assess the impact of tSMS on the prefrontal contributions to inhibitory control and response selection by means of a RNG task. MethodsWe applied 20 min of tSMS over the left DLPFC of healthy subjects, using a real/sham cross-over design, during performance of a RNG task. We used an index of randomness calculated with the measures of entropy and correlation to assess the impact of stimulation on DLPFC function. ResultsThe randomness index of the sequences generated during the tSMS intervention was significantly higher compared to those produced in the sham condition. ConclusionsOur results indicate that application of tSMS transiently modulates specific functional brain networks in DLPFC, which indicate a potential use of tSMS for treatment of neuropsychiatric disorders. SignificanceThis study provides evidence for the capacity of tSMS for modulating DLPFC function.

Effect size for the reduction of corticospinal excitability induced by transcranial static magnetic field stimulation

Effect size for the reduction of corticospinal excitability induced by transcranial static magnetic field stimulation

The effects of unilateral and bilateral transcranial static magnetic field stimulation over the premotor cortex on simple and choice reaction times

The effects of unilateral and bilateral transcranial static magnetic field stimulation over the premotor cortex on simple and choice reaction times

Static magnetic field stimulation over motor cortex modulates resting functional connectivity in humans

Focal application of transcranial static magnetic field stimulation (tSMS) over the human motor cortex induces local changes in cortical excitability. Whether tSMS can also induce distant network effects, and how these local and distant effects may vary over time, is currently unknown. In this study, we applied 10 min tSMS over the left motor cortex of healthy subjects using a real/sham parallel design. To measure tSMS effects at the sensori-motor network level, we used resting-state fMRI. Real tSMS, but not sham, reduced functional connectivity within the stimulated sensori-motor network. This effect of tSMS showed time-dependency, returning to sham levels after the first 5 min of fMRI scanning. With 10 min real tSMS over the motor cortex we did not observe effects in other functional networks examined (default mode and visual system networks). In conclusion, 10 min of tSMS over a location within the sensori-motor network reduces functional connectivity within the same functional network.

Distinct hemispherical responsiveness to transcranial static magnetic field stimulation?

Distinct hemispherical responsiveness to transcranial static magnetic field stimulation?

Transient Modulation of Working Memory Performance and Event-Related Potentials by Transcranial Static Magnetic Field Stimulation over the Dorsolateral Prefrontal Cortex

Transcranial static magnetic field stimulation (tSMS) can modulate human cortical excitability and behavior. To better understand the neuromodulatory effect of tSMS, this study investigates whether tSMS applied over the left dorsolateral prefrontal cortex (DLPFC) modulates working memory (WM) performance and its associated event-related potentials (ERPs). Thirteen healthy participants received tSMS or sham stimulation over the left DLPFC for 26 min on different days. The participants performed a 2-back version of the n-back task before, during (20 min after the start of stimulation), immediately after, and 15 min after the stimulation. We examine reaction time for correct responses, d-prime reflecting WM performance, and the N2 and P3 components of ERPs. Our results show that there was no effect of tSMS on reaction time. The d-prime was reduced, and the N2 latency was prolonged immediately after tSMS. These findings indicate that tSMS over the left DLPFC affects WM performance and its associated electrophysiological signals, which can be considered an important step toward a greater understanding of tSMS and its use in studies of higher-order cognitive processes.

Null Effect of Transcranial Static Magnetic Field Stimulation over the Dorsolateral Prefrontal Cortex on Behavioral Performance in a Go/NoGo Task.

The purpose of this pilot study was to investigate whether transcranial static magnetic field stimulation (tSMS), which can modulate cortical excitability, would influence inhibitory control function when applied over the dorsolateral prefrontal cortex (DLPFC). Young healthy adults (n = 8, mean age ± SD = 24.4 ± 4.1, six females) received the following stimulations for 30 min on different days: (1) tSMS over the left DLPFC, (2) tSMS over the right DLPFC, and (3) sham stimulation over either the left or right DLPFC. The participants performed a Go/NoGo task before, immediately after, and 10 min after the stimulation. They were instructed to extend the right wrist in response to target stimuli. We recorded the electromyogram from the right wrist extensor muscles and analyzed erroneous responses (false alarm and missed target detection) and reaction times. As a result, 50% of the participants made erroneous responses, and there were five erroneous responses in total (0.003%). A series of statistical analyses revealed that tSMS did not affect the reaction time. These preliminary findings suggest the possibility that tSMS over the DLPFC is incapable of modulating inhibitory control and/or that the cognitive load imposed in this study was insufficient to detect the effect.

In vivo local transcranial static magnetic field stimulation alters motor behavior in normal rats

Transcranial static magnetic field stimulation (tSMS) has inhibitory neuromodulatory effects on the human brain. Most of the studies on static magnetic fields have been performed in vitro. To further understand the biological mechanisms of tSMS, we investigated the effects of in vivo tSMS on motor behavior in normal awake rats. The skull of a male Wistar rat was exposed and a polyethylene tube was attached to the skull using dental cement at the center of the motor cortex (n = 7) or the other cortex (n = 6). By attaching a cylindrical NdFeB neodymium magnet into the tube, in vivo tSMS (REAL) was performed. For SHAM, we applied a similar size non-magnetic stainless-steel cylinder. All rats received twice each SHAM and REAL stimulation every two days using a crossover design, and motor function was measured during the stimulation. Activity level and asymmetry of forelimb use were not affected, but less accurate movements in the horizontal ladder test were found in REAL stimulation of the motor cortex. This study shows that in vivo tSMS has inhibitory neuromodulatory effects on motor behavior depending on the stimulated region on the rat cortex.

Ten minutes of transcranial static magnetic field stimulation does not reliably modulate motor cortex excitability.

Recently, modulatory effects of static magnetic field stimulation (tSMS) on excitability of the motor cortex have been reported. In our previous study we failed to replicate these results. It was suggested that the lack of modulatory effects was due to the use of an auditory oddball task in our study. Thus, we aimed to evaluate the role of an oddball task on the effects of tSMS on motor cortex excitability. In a within-subject-design we compared 10 minutes tSMS with and without oddball task. In one of the two sessions subjects had to solve an auditory oddball task during the exposure to the magnet, whereas there was no task during exposure in the other session. Motor cortex excitability was measured before and after tSMS. No modulation was observed in any condition. However, when data were pooled regarding the order of the sessions, a trend for an increase of excitability was observed in the first session compared to the second session. We now can rule out that the auditory oddball task destroys tSMS effects, as postulated. Our results rather suggest that fluctuations in the amplitudes of single pulse motor evoked potentials may possibly mask weak modulatory effects but may also lead to false positive results if the number of subjects in a study is too low. In addition, there might be a habituation effect to the whole procedure, resulting in less variability when subjects underwent the same experiment twice.

Transcranial Static Magnetic Field Stimulation of the Motor Cortex in Children.

BackgroundNon-invasive neuromodulation is an emerging therapy for children with early brain injury but is difficult to apply to preschoolers when windows of developmental plasticity are optimal. Transcranial static magnetic field stimulation (tSMS) decreases primary motor cortex (M1) excitability in adults but effects on the developing brain are unstudied.Objective/HypothesisWe aimed to determine the effects of tSMS on cortical excitability and motor learning in healthy children. We hypothesized that tSMS over right M1 would reduce cortical excitability and inhibit contralateral motor learning.MethodsThis randomized, sham-controlled, double-blinded, three-arm, cross-over trial enrolled 24 healthy children aged 10–18 years. Transcranial Magnetic Stimulation (TMS) assessed cortical excitability via motor-evoked potential (MEP) amplitude and paired pulse measures. Motor learning was assessed via the Purdue Pegboard Test (PPT). A tSMS magnet (677 Newtons) or sham was held over left or right M1 for 30 min while participants trained the non-dominant hand. A linear mixed effect model was used to examine intervention effects.ResultsAll 72 tSMS sessions were well tolerated without serious adverse effects. Neither cortical excitability as measured by MEPs nor paired-pulse intracortical neurophysiology was altered by tSMS. Possible behavioral effects included contralateral tSMS inhibiting early motor learning (p < 0.01) and ipsilateral tSMS facilitating later stages of motor learning (p < 0.01) in the trained non-dominant hand.ConclusiontSMS is feasible in pediatric populations. Unlike adults, tSMS did not produce measurable changes in MEP amplitude. Possible effects of M1 tSMS on motor learning require further study. Our findings support further exploration of tSMS neuromodulation in young children with cerebral palsy.

Transcranial Static Magnetic Field Stimulation Over the Temporal Cortex Modulating the Right Ear Advantage in Dichotic Listening

Transcranial static magnetic field stimulation (tSMS) has proposed a new, promising, and simple non-invasive brain stimulation method. While several studies gained certain evidence about tSMS effects in the motor, somatosensory, and visual domains, there is still a controversial debate about its general effectiveness. In the present study, we investigated potential tSMS effects on auditory speech processing as measured by a dichotic listening (DL) task. Fifteen healthy participants received in randomized order on three different days one session of either sham, tSMS over the left, or tSMS over the right auditory cortex (AC). Under stimulation, participants performed a standard DL task with consonant-vowel syllables. Simultaneously, we recorded electroencephalogram from central sites (Fz, Cz, Pz). TSMS over the left AC changed the behavioral performance and modulated auditory evoked potentials. Stimulation of the left AC significantly reduced the right ear advantage during the DL task and the N1 component of auditory evoked potentials in response to these syllables. The preliminary results of the present exploratory study demonstrate the ability of tSMS to modulate human brain activity on a behavioral as well as physiologic level. Furthermore, tSMS effects on acoustic processing may have clinical implications by fostering potential approaches for a treatment of speech-related pathologies associated with hyperexcitability in the AC.

P76 Motor cortex excitability is not reliably modulated by transcranial static magnetic field stimulation

P76 Motor cortex excitability is not reliably modulated by transcranial static magnetic field stimulation

The effects of transcranial static magnetic fields stimulation over the supplementary motor area on anticipatory postural adjustments

We investigated the influence of transcranial static magnetic field stimulation (tSMS) over the supplementary motor area (SMA) on anticipatory postural adjustments (APAs), in which the activation of the postural muscles of the legs and trunk that control standing posture precedes the activation of the prime mover muscles during rapid shoulder flexion movement. Eighteen subjects performed a self-paced rapid shoulder flexion task before, during, and after tSMS. Electromyogram (EMG) activity was recorded from the deltoid anterior (AD) as the prime mover muscle and the biceps femoris (BF) as the postural muscle during the task. The EMG latency difference (ΔEMG onset) between the two muscles was calculated by subtracting the EMG burst onset of the BF from that of the AD. The ΔEMG onset was significantly shortened, but center-of-pressure parameters were not affected after tSMS stimulation. These findings suggest that tSMS applied over the SMA could inhibitively modulate APAs function.