Universal and differential effects of prefrontal transcranial electrical stimulation on convergent and divergent thinking.

Therapies for major depressive episodes (MDEs) in major depressive disorder (MDD) and bipolar disorder (BD) have limited efficacy and tolerability. Transcranial electrical stimulation (tES), including transcranial direct current (tDCS), alternating current (tACS), and random noise stimulation (tRNS), has been investigated as a non-invasive alternative, but existing reviews are outdated or narrow in scope. A systematic review of tES modalities for MDE in MDD and BD was conducted, alongside a meta-analysis restricted to tDCS RCTs. Eligible participants had MDD or BD diagnosed per standardised criteria. The primary outcome was change in depression severity; secondary outcomes were response and remission. Moderator and sensitivity analyses were performed post hoc. Thirty-four tES trials met inclusion criteria; 31 used tDCS (n=1833 at endpoint) and were eligible for meta-analysis. Pooled results showed active tDCS produced a moderate reduction in depressive symptoms versus sham (Hedges' g=0.387, 95% CI: 0.192-0.582), with no significant effect on response (OR=1.397) or remission (OR=1.138). Larger effects were observed in bipolar depression, monotherapy samples, and studies using F3/F4 electrode placement. No publication bias was detected. Risk of bias ratings influenced effect sizes. tDCS demonstrates statistical superiority to sham for symptom reduction, but effects do not reliably translate to response or remission, and heterogeneity remains substantial. Efficacy varies by clinical and methodological factors. tDCS is a safe, moderately effective option for MDEs. Future trials should improve methodological rigor, refine montage selection, and evaluate longer or multi-channel protocols.

Low intensity transcranial electric stimulation: Safety, ethical, legal regulatory and application guidelines (2017-2025: An update) - endorsed by the European Society for Brain Stimulation (ESBS) and by the International Federation for Clinical Neurophysiology (IFCN).

Brain stimulation prevents neural downregulation and optimizes learning.

Sleep is essentially contributing to human health and well-being through multiple biological functions, including restoration and biosynthesis, brain clearance, energy metabolism, immunological and endocrine processing, synaptic plasticity, memory consolidation, and regulation of cognitive and emotional processes. Sleep disturbances are highly prevalent and are both a symptom and a contributing risk factor for psychiatric, neurological, and somatic disorders. Given the limitations of pharmacological interventions, noninvasive neuromodulation techniques ranging from noninvasive transcranial [transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), transcranial alternating current stimulation (tACS), transcranial random noise stimulation (tRNS), temporal interference stimulation (tTIS), and transcranial ultrasound stimulation (TUS)] to peripheral sensory (auditory, olfactory, visual, tactile, vestibular) and electrical nerve (galvanic vestibular, transcutaneous vagus nerve, and median nerve) stimulation have gained increasing attention as potential tools to modulate sleep physiology. These techniques offer promising avenues for both therapeutic applications and fundamental research into sleep-dependent neuroplasticity, interregional communication, and oscillatory activity. However, sleep is not a uniform state but a highly complex and dynamic phenomenon, with intricate macrostructural [e.g., non-rapid eye movement (NREM)-rapid eye movement (REM) sleep balance, sleep efficiency] and microstructural (e.g., hierarchically nested slow waves and spindles) characteristics that contribute to a variety of functions. This complexity necessitates precise targeting strategies, often employing real-time brain state-dependent stimulation, to modulate specific sleep-related processes effectively. In this review, we summarize the functions of sleep and the available noninvasive tools for its modulation, addressing key methodological challenges and providing recommendations for best practices in sleep neuromodulation.

We conducted this experiment with the aim of investigating the effects of different noise levels from ventilation fans on the growth and slaughter performance, meat quality, blood parameters, and feeding behavior of geese from 21 to 70 days of age. A total of 108 male geese (21-day-old) were randomly assigned to one of three conditions: a control group (no additional fan noise), low-noise treatment (65-75 dB), and high-noise treatment (85-95 dB). Each treatment included six replicates, with six geese per replicate. The results showed that neither ventilation fan noise level significantly affected growth performance, feeding behavior, slaughter performance, or major meat quality traits (p > 0.05). Compared with the control group, noise exposure significantly reduced circulating adrenocorticotropic hormone and corticosterone concentrations (p < 0.05), and the low-noise group exhibited significantly reduced cortisol concentrations (p < 0.05), while the high-noise group had increased cortisol concentrations. Under noise exposure conditions, no statistically significant effects were observed on superoxide dismutase, total antioxidant capacity, malondialdehyde concentration, catalase, and glutathione peroxidase activities compared with the control group (p > 0.05). Overall, prolonged noise stimulation (65-75 dB and 85-95 dB) alleviated stress responses in commercial geese aged 21-70 days, without negatively affecting their growth performance, slaughter performance, meat quality, or feeding behavior.

Prolonged cognitive imbalance, induced by directing attention to one visual field, can paradoxically enhance performance in the opposite, nonattended visual field. This effect is likely driven by the brain's homeostatic mechanisms that regulate excitation and inhibition between hemispheres in homotopic attention processing regions. Here, we employed transcranial random noise stimulation (tRNS) to modulate cortical excitability and probe its role in interhemispheric dynamics controlling visual attention. Specifically, we used a procedure called attentional isolation, where neurotypical participants covertly focused their visual attention in one hemifield (the attended visual field) for 30 min. Performance changes in both the unattended (opposite) visual field and the attended visual field were measured following this manipulation. We applied tRNS over the right or left frontoparietal cortex to modulate the excitability of one hemisphere relative to the other during attention isolation, probing the neural mechanisms underlying the observed contralateral performance shift. Our results showed improved performance in the previously unattended visual field following the attentional isolation period after sham stimulation. However, tRNS revealed a functional dissociation between the hemispheres: Right hemisphere active stimulation abolished the performance improvement, while left hemisphere stimulation preserved it. These findings suggest distinct roles for the left and right hemispheres in modulating paradoxical visual performance shifts and may inform the development of novel neurorehabilitation strategies for clinical populations.

Effects of personalized vs. non-personalized neurostimulation protocols in improving speech and limb reaction times.

Harnessing plasticity potential of the brain: A perspective on transcranial random noise stimulation for learning.

Auditory imagery depends on temporal-cortical mechanisms that generate and sustain internal sound representations. If these mechanisms are causally involved, externally perturbing temporal cortex should alter the quality of imagery. We tested whether bilateral high-frequency transcranial random noise stimulation (hf-tRNS) over temporal cortex alters the vividness and control of auditory imagery. Forty-nine healthy adults completed two sessions on separate days, receiving Active hf-tRNS in one session and Sham in the other (order counterbalanced). The Bucknell Auditory Imagery Scale (BAIS; Vividness and Control subscales) was administered as two parallel half-forms to avoid item repetition; across the two sessions each participant completed the full BAIS, and the half-form paired with the Active session was counterbalanced across participants. Results showed reduced Control ratings under Active hf-tRNS compared with Sham, while Vividness showed a similar but weaker pattern. The effect was independent of which half was completed during Active hf-tRNS, the day-to-half mapping, the stimulation order, or prior musical training. These findings indicate that bilateral hf-tRNS can transiently disrupt the volitional control of internally generated auditory representations, plausibly by perturbing temporal-cortical dynamics that support auditory imagery.

Accurately decoding emotions from facial and vocal cues is essential to successful social interaction. The human mirror neuron system (hMNS) is thought to support this through sensorimotor simulation of observed emotional expressions. While prior studies linked hMNS activity-indexed by mu rhythm desynchronization (mu-ERD)-to emotional action perception, causal evidence with dynamic, multimodal social stimuli remains limited. We investigated whether transcranial random noise stimulation (tRNS) to the inferior frontal cortex (IFC), a key node of the hMNS, enhances perception of static and dynamic emotional displays. Fifty-two participants received active or sham tRNS over the IFC. Consistent with pre-registered predictions, active tRNS led to better performance on static emotion perception tasks compared to sham, with no group difference on a static identity-matching control task-validating stimulation specificity. Extending prior work, active tRNS led to faster response times and greater mu-ERD measured by EEG during dynamic audio-visual emotion perception tasks, consistent with predictions relating to enhanced sensorimotor simulation. These findings suggest that tRNS to the IFC can augment rapid, embodied emotion perception-particularly when stimuli more closely approximate real-world social communication-and contribute to the causal mapping of the hMNS, opening new avenues for studying social-emotional function in neurotypical and clinical populations.

Cognitive deficits in schizophrenia significantly hinder functional outcomes and often remain unresponsive to conventional treatments. While initial evidence suggested potential pro-cognitive effects of electrical brain stimulation in schizophrenia, recent meta-analyses have not supported these findings, warranting further investigation on intervention optimization. This sham-controlled crossover study explored cognitive and emotional effects of bilateral dorsolateral prefrontal cortex (DLPFC) anodal transcranial direct current stimulation (tDCS) and high-frequency transcranial random noise stimulation (tRNS) in schizophrenia. Thirty-six male patients with schizophrenia participated in a crossover trial, receiving three sessions (tDCS, tRNS, sham) in counterbalanced order with 1-week intervals. tDCS and tRNS sessions involved 20-min 2 mA anodal stimulation and 2 mA 100-640 Hz random noise stimulation targeting the left and right DLPFCs (F3-F4) with two extracephalic return electrodes. Executive functions (working memory, spatial planning) were assessed during stimulation, and emotional changes were measured with the Positive and Negative Affect Schedule (PANAS) pre- and post-stimulation. Additionally, side effects and blinding efficacy were evaluated. Both bilateral DLPFC anodal tDCS and high-frequency tRNS significantly improved planning performance (mean problems solved, mean number of moves) compared to sham, with tRNS additionally enhancing working memory accuracy and strategy score. Both interventions increased positive affect and reduced negative affect after the intervention, with tRNS showing greater enhancement of positive emotions. Reduced negative affect after tRNS was correlated with improved executive planning. Side effects were minimal, and blinding was effective for the sham condition. Bilateral DLPFC anodal tDCS and high-frequency tRNS show promise as adjunctive treatments for schizophrenia, especially for cognitive deficits, with broader cognitive and emotional benefits observed with tRNS. ClinicalTrials.gov Identifier: NCT06155786 https://clinicaltrials.gov/study/NCT06155786 .

To assess the combined effect of high-definition transcranial random noise stimulation (HD-tRNS) of bilateral auditory cortex and acoustic stimulation (AS) on auditory evoked potentials and tinnitus perception. A double-blind, randomized, controlled, within-subject crossover trial was conducted with thirteen adults with chronic tinnitus. Each participant completed four sessions, at least 48 h apart, consisting of active HD-tRNS + AS, active HD-tRNS alone, sham HD-tRNS + sham AS and sham HD-tRNS alone. Auditory evoked potentials (including mismatch negativity) and tinnitus characteristics were measured before and after each session. Active electric and bimodal stimulation significantly modulated auditory evoked potentials, unlike their sham equivalents. Bimodal stimulation produced significant changes in MMN amplitude that countered the tinnitus-related alteration in processing intensity deviants. However, these effects did not survive family-wise correction in this complex design. Bimodal and bimodal-sham stimulation reduced objective loudness by >3 dB. HD-tRNS, particularly when combined with AS, may induce changes in auditory-system excitability and acutely alter neural processing and loudness perception in tinnitus. Combining acoustic and electric stimulation is a promising approach for basic research and clinical applications in auditory neuroscience, providing new insights into neuroplasticity in an altered auditory system. This is the first study to measure the modifiability of evoked neural correlates in tinnitus.

Emerging evidence highlights the potential role of auditory stimulation in enhancing sleep-dependent memory consolidation. Pink noise appears to be an effective auditory stimulus for enhancing memory consolidation, likely due to its wide-range influence on brain oscillations. However, the specific underlying mechanisms by which pink noise enhances memory consolidation remain unclear. This perspective article presents a novel hypothesis exploring how pink noise, delivered through closed-loop auditory stimulation, may facilitate memory consolidation. Specifically, we suggest that pink noise may reach the hippocampus via the rapid auditory pathway, potentially increasing the likelihood of sharp-wave ripple (SW-R) generation. By increasing hippocampal ripple activity, the overall likelihood of synchronization with spindles and slow oscillations is also increased, enhancing hippocampal–cortical coupling. This suggests that pink noise might indirectly support slow oscillation-ripple-spindle coordination to promote systems-level consolidation and interregional information transfer. This, in turn, could enable long-term memory storage and support abstraction and generalization. Our hypothesis emphasizes a bottom-up mechanism originating from the hippocampus. Although this hypothesis currently lacks direct support from subcortical recordings, it builds on existing knowledge of sleep rhythms, hippocampal auditory pathways, and the known effects of SW-R modulation on memory formation. This perspective offers a framework for future work investigating the mechanisms by which pink noise stimulation can lead to memory enhancement.

Exercise and primary motor cortex (M1) stimulation may alleviate pain by enhancing the endogenous pain-inhibitory system, with its efficacy assessed through conditioned pain modulation (CPM). This study examined whether combining exercise with M1-targeted transcranial electrical stimulation enhances CPM more effectively than either intervention alone. Two randomized, sham-controlled experiments were conducted. In Experiment 1 (N = 70), participants completed a 3-min isometric handgrip exercise or quiet rest. In Experiment 2 (N = 140), participants received 20 min of M1-targeted transcranial random noise stimulation with direct current offset (tRNS + DC-offset) or sham stimulation, followed by either exercise or rest. CPM was assessed at baseline, immediately after, and 30 min post-intervention. Results showed that exercise alone did not significantly enhance CPM efficacy. In contrast, M1-targeted tRNS + DC-offset significantly enhanced CPM efficacy at both post-intervention time points. Critically, individuals with low baseline CPM showed greater benefits from the combination of tRNS + DC-offset and exercise compared to either exercise alone or tRNS + DC-offset alone, particularly at 30 min post-intervention. These results highlight the potential of combining motor cortex stimulation with exercise to optimize endogenous pain inhibition, particularly as a personalized, nonpharmacological intervention for individuals with impaired pain modulation.

Background/Objectives: Transcranial electrical stimulation (tES) shows potential for enhancing attention and learning, yet its effects in applied contexts remain underexplored. This study investigated whether transcranial direct current stimulation (tDCS) either alone or in combination with high-frequency transcranial random noise stimulation (hf-tRNS) over the right inferior frontal gyrus (rIFG) could enhance performance in a visual search task requiring target identification and change detection, compared with a low-current control condition. Methods: Sixty-four participants were randomly assigned to receive tDCS alone (2.0 mA), tDCS with hf-tRNS (1.8 mA DC offset combined with 100–500 Hz noise at ±0.18 mA), or low-current control stimulation during training. The task involved identifying vehicles and detecting changes between image presentations. Performance accuracy and EEG oscillatory power were assessed at baseline and post-stimulation. Results: ANCOVA revealed significant effects of stimulation on target identification accuracy (F(2,60) = 3.27, p = 0.045, ηp2 = 0.098), with tDCS showing greater improvement than the low-current control condition (p = 0.017). No significant effects were found for change detection for any stimulation condition, or for either the target or change detection for hf-tRNS. Baseline performance moderated stimulation effects: low performers receiving tDCS showed the greatest improvements (F(2,26) = 3.80, p = 0.036, ηp2 = 0.226), surpassing even high-baseline performers post-training. EEG analyses revealed that participants who showed greater decreases in frontal theta power demonstrated larger improvements in accuracy with tDCS alone (r = −0.634, p = 0.005) but not with hf-tRNS or the control. Conclusions: tDCS over rIFG selectively enhanced target identification accuracy in a complex visual search, particularly benefiting individuals with lower-baseline performance. These findings suggest tDCS may facilitate training in lower-performing novice populations.

Anxiety is a beneficial behavior that assists survival, although when high levels of anxiety persist it can hinder normal functioning. Despite numerous treatment options most individuals with Generalized Anxiety Disorder (GAD) continue to suffer from the disorder. A novel neuromodulatory treatment that safely and non-invasively alters pathological neural circuitry associated with GAD is required. Therefore, this study investigates the feasibility, safety, and effect of a new innovative High-Definition Transcranial Infraslow Gray Noise Stimulation (HD-tIGNS) targeting the anxiety network in people with GAD, in a delayed-start double-blinded randomized sham-controlled pilot trial (N = 22). HD-tIGNS was applied three times per week for three [delayed-start (following 3-weeks of actisham)], or six weeks (early-start). Anxiety questionnaires and electroencephalography were taken at baseline, mid-treatment, and post-treatment. On average, six participants were recruited per month with a mean treatment adherence of 99.5%, and an 8.3% dropout rate of enrolled participants. Clinically meaningful changes in GAD-7 were observed in 45% (early-start group) and 36% (delayed-start group) of participants following 6-weeks and 3-weeks of intervention respectively. No significant differences in brain activity or functional connectivity were observed. This study provides evidence supporting HD-tIGNS as a safe and feasible treatment approach for GAD, however future research should consider alternate network targets.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-27624-3.

Reducing attention bias toward negative emotional stimuli with transcranial random noise stimulation: a randomized, double-blind, sham-controlled, crossover study.

The aim of this article is to present current research and conclusions regarding the effectiveness, mechanisms of action, and clinical applications of neuromodulation methods-such as transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), transcranial alternating current stimulation (tACS), transcranial random noise stimulation (tRNS), and noisy galvanic vestibular stimulation (nGVS)-in the treatment of depressive and anxiety disorders, with particular emphasis on their neurobiological foundations. Neuromodulation represents a novel, promising therapeutic strategy in the treatment of affective and anxiety disorders, especially in patients resistant to pharmacotherapy and psychotherapy. Techniques using electrical and electromagnetic modulation have demonstrated antidepressant effects that may constitute an important component of the therapeutic approach in these disorders. Transcranial magnetic stimulation and transcranial direct current stimulation influence prefrontal–limbic circuits, normalizing functional connectivity through the regulation of cortical excitability and activation of signaling pathways involving brain-derived neurotrophic factor (BDNF). More recent techniques such as tACS and tRNS enable frequency-specific modulation of neuronal oscillations, showing promising results in treatment-resistant depression. The routine use of neuromodulation in depressive and anxiety disorders-particularly when other treatments have proven ineffective-may become a new therapeutic paradigm in psychiatry. However, further clinical studies are required to standardize stimulation parameters and assess the long-term efficacy of these methods.

Transcranial random noise stimulation (tRNS) is a non-invasive brain stimulation technique that modulates cortical excitability through stochastic resonance. While promising, its safety and efficacy in psychiatric disorders remain underexplored. To systematically evaluate the efficacy and safety of tRNS in various psychiatric disorders. A systematic review was conducted per PRISMA guidelines and registered on PROSPERO (CRD420251040192). Databases searched included CENTRAL-Cochrane Central Register of Controlled Trials, PubMed, Scopus, and Web of Science. Studies were included from their inception to 30th April, 2025. Studies involving tRNS in psychiatric populations, regardless of study design, were included. The risk of bias was assessed using JBI tools. 22 studies were included (642 individuals), spanning ADHD, depression, schizophrenia, dyslexia, and other conditions. Most studies used 20-minute tRNS sessions over 1-4 weeks. ADHD and dyslexia showed consistent improvements in overall executive function and reading & phonological skills, respectively. Schizophrenia studies demonstrated significant reductions in negative symptoms and auditory hallucinations. Effects in depression were mixed, with some studies reporting substantial symptom relief, while others found no significant benefit. Across disorders, tRNS was generally well-tolerated with only mild, transient adverse effects. tRNS appears to be a safe, well-tolerated, and potentially effective intervention for specific psychiatric symptoms, especially in ADHD, dyslexia, and schizophrenia. However, inconsistent protocols and mixed outcomes in mood disorders highlight the need for standardized protocols and further research.