The effects of 400 Hz anodal and cathodal transcranial pulsed current stimulation of the primary motor cortex (400 Hz a-tPCS M1, 400 Hz c-tPCS M1) on corticospinal excitability (CSE) and corticocortical excitability (CCE) remain underexplored. This study examined the effects of 400 Hz a-tPCS M1, 400 Hz c-tPCS M1, and sham stimulation on CSE, CCE, and hand dexterity, providing insights for potential clinical applications in motor deficits. In this double-blinded, randomized, counterbalanced crossover trial, 26 healthy young adults completed three experimental sessions: 400 Hz a-tPCS M1, 400 Hz c-tPCS M1, and sham stimulation, spaced 48 hours apart. Transcranial magnetic stimulation assessed CSE and CCE, while the Purdue Pegboard Test (PPT) evaluated hand dexterity. The results showed polarity-specific effects. A single session of 400 Hz a-tPCS M1 significantly increased CSE and improved hand dexterity, evidenced by faster PPT completion times (p < 0.05). Conversely, 400 Hz c-tPCS M1 reduced CSE but did not influence PPT performance (p > 0.05). Sham stimulation showed no significant changes. These findings suggest that 400 Hz a-tPCS M1 enhances motor excitability and dexterity, while 400 Hz c-tPCS M1 selectively reduces CSE. This study lays a foundation for exploring high-frequency tPCS in clinical motor rehabilitation.

backend=biber, style=alphabetic, sorting=ynt ]biblatex Objectives: This study compares the effects of two bifocal single session 400 Hz pulsed current stimulation (tPCS) montages, anodal tPCS over M1 with cathodal tPCS over the CB (a-tPCS M1–c-tPCS CB; Montage 1) and cathodal tPCS over M1 with anodal tPCS over the CB (c-tPCS M1–a-tPCS CB; Montage 2), on corticospinal excitability (CSE), corticocortical excitability (CCE), and hand dexterity. The findings aim to inform neuromodulation strategies for motor rehabilitation. Methods This double-blinded, randomized, counterbalanced crossover trial included 26 healthy young participants, each completing three sessions: Montage 1, Montage 2, and sham stimulation. Data were collected before and immediately after each stimulation session, with a minimum 48-hour washout period to prevent carryover effects. CSE and CCE were assessed using transcranial magnetic stimulation (TMS), while hand dexterity was evaluated using the Purdue Pegboard Test (PPT). Results A single session of Montage 1 (a-tPCS M1–c-tPCS CB) significantly enhanced CSE and improved motor performance, as demonstrated by faster completion times on the PPT (p < 0.05). In contrast, Montage 2 (c-tPCS M1–a-tPCS CB) significantly reduced CSE but did not significantly affect PPT performance (p > 0.05). Conclusions These findings suggest that Montage 1 enhances CSE and hand dexterity, supporting its potential application in motor rehabilitation. The primary mechanisms underlying this increase in CSE were enhanced facilitation and reduced inhibition. In contrast, Montage 2 decreased CSE but did not lead to significant changes in hand dexterity, emphasizing the need for further investigation into its neuromodulatory mechanisms and potential clinical applications. The reduction in facilitation and increased inhibition were the key factors contributing to the decrease in CSE.

Introduction: The underlying mechanisms of transcranial pulsed current stimulation (tPCS), a non-invasive neuromodulation technique, have attracted significant interest in recent years. However, the effects of anodal tPCS (a-tPCS) applied at alpha (8-12 Hz), beta (13-30 Hz), and gamma (30-100 Hz) frequencies remain underexplored. This study aimed to investigate the a-tPCS effects at 10, 25, and 80 Hz on cortical outcomes and adverse side effects. Methods: This double-blinded, randomized, counterbalanced crossover trial involved 15 healthy participants selected based on a power analysis. All participants completed four experimental sessions with 2mA stimulation for 20 minutes at randomized frequencies. Single-pulse and paired-pulse transcranial magnetic stimulation (TMS) over the primary motor cortex (M1) were applied pre- and post-assessments. A minimum 48-hour washout period was implemented to prevent carry-over effects between sessions. Results: The results indicated that a single session of a-tPCS at frequencies of 10, 25, and 80 Hz enhanced corticospinal excitability (CSE) compared to sham stimulation ( p < 0.05). The CSE-increased changes at 10 Hz (64.58%) and 25 Hz (44.82%) showed concurrent modulation of intracortical facilitation (ICF) and mild side effects during stimulation. However, the CSE-increased changes at 80 Hz (27.66%) coincided with a reduction in short intracortical inhibition (SICI), alongside minimal side effects and no phosphene perception. Conclusion: The results indicate that alpha-gamma range frequencies of a-tPCS increased CSE through glutamate-mediated pathways, whereas gamma-frequency stimulation may engage counter-regulatory GABAergic mechanisms. Thus, tPCS, as a neuromodulation technique that modulates neuroplasticity through frequency-dependent mechanisms, may offer a safer and more affordable option for vulnerable populations with fewer adverse effects. However, further research and clinical validation are needed to establish the efficacy of tPCS relative to other non-invasive brain stimulation techniques.

Inconsistent results are observed in the effects of transcranial direct current stimulation (tDCS) with different montages on motor learning. This study aimed to compare the effects of anodal and cathodal tDCS over primary motor cortex (M1) at different intensities (1 and 2 mA) on motor learning in healthy young adults. The participants were randomly divided to five groups: 1) 1mA M1 c-tDCS, 2) 1mA M1 a-tDCS, 3) 2 mA M1 c-tDCS, 4) 2 mA M1 a-tDCS and 5) M1 sham tDCS. The groups received 20-minute stimulation concurrent with serial response time test (SRTT) implicitly, while the tDCS was turned off after 30 seconds in the sham tDCS group. Response time (RT) and error rate (ER) during SRTT were assessed prior, during and 72 hours after the intervention. The results indicated that online learning occurred in all groups (P < 0.05), except in M1 c-tDCS (1 mA) (P>0.05). In addition, offline learning was observed in 1 mA M1 a-tDCS, 2mA M1 a-tDCS and 2 mA M1 c-tDCS as compared to sham tDCS and M1 c-tDCS (1 mA) groups (P < 0.05). On the other hand, 1 mA M1 c-tDCS group did not indicate any consolidation effect and even a trend toward negative offline learning. M1 a-tDCS with different intensities and also 2 mA M1 c-tDCS may be helpful for the enhancement of motor learning in young adults. Considering the deterioration effect of 1 mA M1 c-tDCS, it seems that caution should be applied in using it to improve motor learning.

Introduction: The rating of perceived exertion (RPE) is a widely used method for monitoring the load during training, as it provides insight into the subjective intensity of effort experienced during exercises. Considering the role of brain in monitoring and perception of the effort, several studies explored the effect of transcranial direct current stimulation (tDCS) on RPE in different populations. The aim of current study is to review the studies investigated the effect of tDCS on RPE in three groups including healthy untrained people, physically active persons and athletes. Method: Nine databases were searched for papers assessing the effect of tDCS on RPE. The data of included studies were extracted and methodological quality examined using the risk of bias 2 (ROB2) tool. Thirty-three studies met the inclusion criteria. Results: According to the meta-analysis, active a-tDCS significantly decreased the RPE compared to the sham-stimulation. The a-tDCS could decrease the RPE when it was applied over M1 or DLPF. Regarding the measurement tool, Borg’s scale 6-20 and OMNI scale could show an improvement in RPE scale. Conclusion: A-tDCS is a promising technique that can decrease improve the RPE. M1 and DLPFC are suggested as the target area of stimulation. From the tools that measure the RPE, Borg’s RPE 6-20 and OMNI scale could better show the effect of a-tDCS.

Transcranial pulsed current stimulation (tPCS) is a promising non-invasive brain stimulation technique that has gained considerable attention in recent years. The purpose of this review is to provide an overview of the existing literature on tPCS, examine the scope and nature of previous research, investigate its underlying mechanisms, and identify gaps in the literature. A search of online databases resulted in 36 published tPCS studies from inception until May 2023. These studies were categorized into three groups: human studies on healthy individuals, patient studies with pathological conditions, and animal studies. The findings suggest that tPCS has the potential to modulate brain excitability by entraining neural oscillations and utilizing stochastic resonance. However, the mechanisms underlying the effects of tPCS are not yet fully understood and require further investigation. Furthermore, the included studies indicate that tPCS may have therapeutic potential for neurological diseases. However, before tPCS can be applied in clinical settings, a better understanding of its mechanisms is crucial. In this regard, the tPCS studies were categorized into four types of research: basic, strategic, applied, and experimental research, to identify the nature of the literature and gaps. Analysis of these categories revealed that tPCS, with its diverse parameters, effects, and mechanisms, presents a wide range of research opportunities for future investigations.