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Transcutaneous spinal direct current stimulation (tsDCS) is an effective non-invasive spinal cord electrical stimulation technique to induce neuromodulation of local and distal neural circuits of the central nervous system (CNS). Applied to the spinal cord lumbosacral region, tsDCS changes electrophysiological responses of the motor, proprioceptive and nociceptive pathways, alters the performance of some lower limb motor tasks and can even modulate the behavior of supramedullary neuronal networks. In this study an experimental protocol was conducted to verify if tsDCS (5 mA, 20 minutes) of two different polarizations, applied over the lumbosacral region (tenth thoracic vertebrae (T10)), can induce changes in postural sway oscillations of young healthy individuals during quiet standing. A novel initialization of the electrical stimulation was developed to improve subject blinding to the different stimulus conditions including the sham trials. Measures of postural sway, both global and structural, were computed before, during and following the DC stimulation period. The results indicated that, for the adopted conditions, tsDCS did not induce statistically significant changes in postural sway of young healthy individuals during quiet standing.

Interindividual anatomical differences in the human cortex can lead to suboptimal current directions and may result in response variability of transcranial electrical stimulation methods. These differences in brain anatomy require individualized electrode stimulation montages to induce an optimal current density in the targeted area of each individual subject. We aimed to explore the possible modulatory effects of 140 Hz transcranial alternating current stimulation (tACS) on the somatosensory cortex using personalized multi-electrode stimulation montages. In two randomized experiments using either tactile finger or median nerve stimulation, we measured by evoked potentials the plasticity aftereffects and oscillatory power changes after 140 Hz tACS at 1.0 mA as compared to sham stimulation (n = 17, male = 9). We found a decrease in the power of oscillatory mu-rhythms during and immediately after tactile discrimination tasks, indicating an engagement of the somatosensory system during stimulus encoding. On a group level both the oscillatory power and the evoked potential amplitudes were not modulated by tACS neither after tactile finger stimulation nor after median nerve stimulation as compared to sham stimulation. On an individual level we could however demonstrate that lower angular difference (i.e., differences between the injected current vector in the target region and the source orientation vector) is associated with significantly higher changes in both P20/N20 and N30/P30 source activities. Our findings suggest that the higher the directionality of the injected current correlates to the dipole orientation the greater the tACS-induced aftereffects are.

Anxiety disorders are among the most prevalent mental disorders. Present treatments such as cognitive behavior therapy and pharmacological treatments show only moderate success, which emphasizes the importance for the development of new treatment protocols. Non-invasive brain stimulation methods such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) have been probed as therapeutic option for anxiety disorders in recent years. Mechanistic information about their mode of action, and most efficient protocols is however limited. Here the fear extinction model can serve as a model of exposure therapies for studying therapeutic mechanisms, and development of appropriate intervention protocols. We systematically reviewed 30 research articles that investigated the impact of rTMS and tDCS on fear memory and extinction in animal models and humans, in clinical and healthy populations. The results of these studies suggest that tDCS and rTMS can be efficient methods to modulate fear memory and extinction. Furthermore, excitability-enhancing stimulation applied over the vmPFC showed the strongest potential to enhance fear extinction. We further discuss factors that determine the efficacy of rTMS and tDCS in the context of the fear extinction model and provide future directions to optimize parameters and protocols of stimulation for research and treatment.

Transcranial magnetic stimulation is an increasingly popular FDA-approved treatment for resistant depression, migraines, and OCD. Research is also underway for its use in various other psychiatric and medical disorders. Although rare, seizures are a potential adverse event of TMS treatment. In this article, we discuss TMS-related seizures with the various coils used to deliver TMS, the risk factors associated with seizures, the differential diagnosis of its presentations, the effects of sleep deprivation and alcohol use on seizures, as well as seizure risks with protocols for traditional TMS, theta-burst stimulation, and accelerated TMS. A discussion is presented comparing the potential risk of seizures with various psychotropic medications versus TMS. Included are case reports of TMS seizures in the child/adolescent patient, bipolar disorder patients, patients with a history of a traumatic brain injury, and those with epilepsy. Reports are also shared on TMS use without seizures in patients with a history of head injuries and TMS's continued use if patients have a seizure during their TMS treatment. Findings generated in this review suggest the following. Seizures, if present, are usually self-limiting. Most treatment recommendations for TMS-related seizures are supportive in nature. The risk of TMS-related seizures is <1% overall. TMS has successfully been used in patients with epilepsy, traumatic brain injuries, and those with a prior TMS-related seizure. The rate of TMS-related seizures is comparable to that of most psychotropic medications. While having a seizure is a rare but serious adverse effect of TMS, the benefits of treating refractory depression with TMS may outweigh the risk of suicidal ideation and other significant complications of depression.

Source monitoring refers to the ability to identify the origin of a memory, for example, whether you remember saying something or thinking about it, and confusions of these sources have been associated with the experience of auditory verbal hallucinations (AVHs). Both AVHs and source confusions are reported to originate from dysfunctional brain activations in the prefrontal cortex (PFC) and the superior temporal gyrus (STG); specifically, it is assumed that a hypoactive PFC and a hyperactive STG gives rise to AVHs and source confusions. We set out to test this assumption by trying to mimic this hypertemporal/hypofrontal model in healthy individuals with transcranial direct current stimulation (tDCS): the inhibitory cathode was placed over the left PFC and the excitatory anode over the left dorsolateral STG. Participants completed a reality monitoring task (distinguishing between external and internal memory sources) and an internal source monitoring task (distinguishing between two or more internal memory sources) in two separate experiments (offline vs. online tDCS). In the offline experiment (n = 34), both source monitoring tasks were completed after tDCS stimulation, and in the online experiment (n = 27) source monitoring tasks were completed while simultaneously being stimulated with tDCS. We found that internal source monitoring abilities were significantly enhanced during active online tDCS, while reality monitoring abilities were unaffected by stimulation in both experiments. We speculate, based on combining the present findings with previous studies, that there might be different brain areas involved in reality and internal source monitoring. While internal source monitoring seems to involve speech production areas, specifically Broca's area, as suggested in the present study, reality monitoring seems to rely more on the STG and DLPFC, as shown in other studies of the field.

Stimulation of deeper brain structures by transcranial magnetic stimulation (TMS) plays a role in the study of reward and motivation mechanisms, which may be beneficial in the treatment of several neurological and psychiatric disorders. However, electric field distributions induced in the brain by deep transcranial magnetic stimulation (dTMS) are still unknown. In this paper, the double cone coil, H-coil and Halo-circular assembly (HCA) coil which have been proposed for dTMS have been numerically designed. The distributions of magnetic flux density, induced electric field in an anatomically based realistic head model by applying the dTMS coils were numerically calculated by the impedance method. Results were compared with that of standard figure-of-eight (Fo8) coil. Simulation results show that double cone, H- and HCA coils have significantly deep field penetration compared to the conventional Fo8 coil, at the expense of induced higher and wider spread electrical fields in superficial cortical regions. Double cone and HCA coils have better ability to stimulate deep brain subregions compared to that of the H-coil. In the mean time, both double cone and HCA coils increase risk for optical nerve excitation. Our results suggest although the dTMS coils offer new tool with potential for both research and clinical applications for psychiatric and neurological disorders associated with dysfunctions of deep brain regions, the selection of the most suitable coil settings for a specific clinical application should be based on a balanced evaluation between stimulation depth and focality.

Studies have confirmed that low-frequency repetitive transcranial magnetic stimulation can decrease the activity of cortical neurons, and high-frequency repetitive transcranial magnetic stimulation can increase the excitability of cortical neurons. However, there are few studies concerning the use of different frequencies of repetitive transcranial magnetic stimulation on the recovery of upper-limb motor function after cerebral infarction. We hypothesized that different frequencies of repetitive transcranial magnetic stimulation in patients with cerebral infarction would produce different effects on the recovery of upper-limb motor function. This study enrolled 127 patients with upper-limb dysfunction during the subacute phase of cerebral infarction. These patients were randomly assigned to three groups. The low-frequency group comprised 42 patients who were treated with 1 Hz repetitive transcranial magnetic stimulation on the contralateral hemisphere primary motor cortex (M1). The high-frequency group comprised 43 patients who were treated with 10 Hz repetitive transcranial magnetic stimulation on ipsilateral M1. Finally, the sham group comprised 42 patients who were treated with 10 Hz of false stimulation on ipsilateral M1. A total of 135 seconds of stimulation was applied in the sham group and high-frequency group. At 2 weeks after treatment, cortical latency of motor-evoked potentials and central motor conduction time were significantly lower compared with before treatment. Moreover, motor function scores were significantly improved. The above indices for the low- and high-frequency groups were significantly different compared with the sham group. However, there was no significant difference between the low- and high-frequency groups. The results show that low- and high-frequency repetitive transcranial magnetic stimulation can similarly improve upper-limb motor function in patients with cerebral infarction.

Transcranial direct current stimulation (tDCS) is used to modulate brain function, and can modulate motor and postural control. While the acute effect of tDCS is well documented on patients, little is still known whether tDCS can alter the motor control of healthy trained participants. This study aimed to assess the acute effect of tDCS on postural control of parkour practitioners, known for their good balance abilities and their neuromuscular specificities that make them good candidates for tDCS intervention. Eighteen parkour practitioners were tested on three occasions in the laboratory for each stimulation condition (2 mA; 20 minutes)-primary motor cortex (M1), dorsolateral prefrontal cortex (dlPFC) and sham (placebo). Postural control was evaluated PRE and POST each stimulation by measuring Center of Pressure (CoP) displacements on a force platform during static conditions (bipedal and unipedal stance). Following M1 stimulation, significant decreases were observed in CoP area in unipedal (from 607.1 ± 297.9 mm.sup.2 to 451.1 ± 173.9 mm.sup.2, P = 0.003) and bipedal (from 157.5 ± 74.1 mm.sup.2 to 117.6 ± 59.8 mm.sup.2 P<0.001) stances. As well, the CoP total length was significantly reduced in bipedal (from 3416.8 ± 295.4 mm to 3280.6 ± 306.2 mm, P = 0.005) as well as in unipedal stance (from 4259.6 ± 398.4 mm to 3846.5 ± 468.9 mm, P<0.001), only after M1 stimulation. Relative pre-post changes observed after M1 stimulation were negatively correlated to experience in parkour only after unipedal stance (r = 0.715, P<0.001), meaning that the more participants were trained the less tDCS was effective. No significant changes were noticed after sham and dlPFC stimulation. These results suggested that the modulation of gait performance in athletes following an acute intervention of tDCS is specific to the targeted brain region, and that postures with reduced base of support (such as unipedal stance) were more sensitive to tDCS.

Objectives This systematic review and meta-analysis aim to summarize and analyze the available evidence of non-invasive brain stimulation/spinal cord stimulation on gait, balance and/or lower limb motor recovery in stroke patients. Methods The PubMed database was searched from its inception through to 31/03/2021 for randomized controlled trials investigating repetitive transcranial magnetic stimulation or transcranial/trans-spinal direct current/alternating current stimulation for improving gait, balance and/or lower limb motor function in stroke patients. Results Overall, 25 appropriate studies (including 657 stroke subjects) were found. The data indicates that non-invasive brain stimulation/spinal cord stimulation is effective in supporting recovery. However, the effects are inhomogeneous across studies: (1) transcranial/trans-spinal direct current/alternating current stimulation induce greater effects than repetitive transcranial magnetic stimulation, and (2) bilateral application of non-invasive brain stimulation is superior to unilateral stimulation. Conclusions The current evidence encourages further research and suggests that more individualized approaches are necessary for increasing effect sizes in stroke patients.

Transcranial magnetic stimulation (TMS) is emerging as a potential broad-spectrum therapy for addiction. In this Opinion article, Diana and colleagues discuss the neural foundations of TMS and discuss possible mechanisms underlying the beneficial effects observed in people with addictions. Substance use disorders (SUDs) are one of the leading causes of morbidity and mortality worldwide. In spite of considerable advances in understanding the neural underpinnings of SUDs, therapeutic options remain limited. Recent studies have highlighted the potential of transcranial magnetic stimulation (TMS) as an innovative, safe and cost-effective treatment for some SUDs. Repetitive TMS (rTMS) influences neural activity in the short and long term by mechanisms involving neuroplasticity both locally, under the stimulating coil, and at the network level, throughout the brain. The long-term neurophysiological changes induced by rTMS have the potential to affect behaviours relating to drug craving, intake and relapse. Here, we review TMS mechanisms and evidence that rTMS is opening new avenues in addiction treatments.