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• Effects of single-session transcranial random noise stimulation (tRNS) over the left DLPFC on pain were assessed. • Pain expectation and perception decreased immediately after tRNS. • Analgesic effects of tRNS were mediated by modulating pain expectation. The dorsolateral prefrontal cortex (DLPFC) has been increasingly used as a neuromodulatory target in pain management. Transcranial random noise stimulation (tRNS) was shown to effectively elevate cortical excitability. Hence, this study aimed to characterize how tRNS over the left DLPFC affects pain expectation and perception, as well as the efficacy of conditioned-pain modulation (CPM) that reflects the function of the endogenous pain-inhibitory pathway. Using a randomized, double-blinded, and sham-controlled design, healthy participants were randomly recruited to receive tRNS with a direct current offset or sham stimulation. Their expectations and perceptions of painful electrocutaneous stimuli, as well as CPM efficacy were assessed before, immediately after, and 30 min after tRNS. Compared with sham stimulation, perceived-pain ratings to the painful stimuli, and expected-pain ratings before painful stimuli, attenuated immediately after tRNS, whereas this analgesic effect was ineffective 30 min after tRNS. Importantly, the immediate analgesia induced by tRNS could be accounted for by tRNS effect on attenuating expected-pain ratings before certain painful stimuli. However, CPM efficacy was not significantly affected by tRNS. These results demonstrate analgesia immediately after applying tRNS over the left DLPFC. This study provides evidence for analgesia of DLPFC-tRNS on an experimental pain model. [ABSTRACT FROM AUTHOR]

Many studies have shown effects of anodal transcranial direct current stimulation (a-tDCS) and high-frequency transcranial random noise stimulation (tRNS) on elevating cortical excitability. Moreover, tRNS with a direct current (DC)-offset is more likely to lead to increases in cortical excitability than solely tRNS. While a-tDCS over primary motor cortex (M1) has been shown to attenuate pain perception, tRNS + DC-offset may prove as an effective means for pain relief. This study aimed to examine effects of a-tDCS and high-frequency tRNS + DC-offset over M1 on pain expectation and perception, and assess whether these effects could be influenced by the certainty of pain expectation. Using a double-blinded and sham-controlled design, 150 healthy participants were recruited to receive a single-session a-tDCS, high-frequency tRNS + DC-offset, or sham stimulation over M1. The expectation and perception of electrical stimulation in certain and uncertain contexts were assessed at baseline, immediately after, and 30 min after stimulation. Compared with sham stimulation, a-tDCS induced immediate analgesic effects that were greater when the stimulation outcome was expected with uncertainty; tRNS induced immediate and sustained analgesic effects that were mediated by decreasing pain expectation. Nevertheless, we found no strong evidence for tRNS being more effective for attenuating pain than a-tDCS. The analgesic effects of a-tDCS and tRNS showed different temporal courses, which could be related to the more sustained effectiveness of high-frequency tRNS + DC-offset in elevating cortical excitability. Moreover, expectations of pain intensity should be taken into consideration to maximize the benefits of neuromodulation. • Effects of a-tDCS and high-frequency tRNS + DC-offset on pain were assessed. • A single-session a-tDCS induced immediate analgesic effects. • A single-session tRNS induced both immediate and sustained analgesic effects. • Analgesic effects of a-tDCS were greater when pain was expected with uncertainty. • Analgesic effects of tRNS were mediated by decreasing pain expectation. [ABSTRACT FROM AUTHOR]

• Participants were asked to rate the pleasantness of musical chords. • hf-tRNS (1.5 mA, offset 0) was applied over the left/right auditory cortex. • Dissonant chords were rated as less pleasant than consonant chords. • hf-tRNS did not influence pleasantness of musical chords. • Unilateral temporal stimulation does not modulate musical pleasantness. The "consonance effect" is the pleasant and unpleasant evaluation attributed to consonant and dissonant music, respectively. Different studies in this domain revealed a left-hemispheric superiority for dissonance and a right-hemispheric superiority for consonance. We investigated the causal relationship between the consonance effect and the activity of the cerebral hemispheres by applying high frequency transcranial Random Noise Stimulation (hf-tRNS) over the left or right auditory cortex in a group of 24 healthy volunteers. Results confirm the consonance effect, dissonant chords being judged as more unpleasant than consonant chords, and show that hf-tRNS does not influence the pleasantness evaluations of chords. We speculate that the auditory cortex is directly involved in consonance and dissonance processing, but that pleasantness evaluations could take place in the anterior areas of the brain. This is the first evidence concerning the effects of the modulatory activity in each cerebral hemisphere and the consonance effect. [ABSTRACT FROM AUTHOR]

Extensive behavioural evidence has shown that older people have declined ability in facial emotion perception. Recent work has begun to examine the neural mechanism that contribute to this, and potential tools to support emotion perception during aging. The aim of this study was to investigate whether high frequency tRNS applied to the inferior frontal cortex would enhance facial expression perception in older adults. Healthy aged adults (60+ years) were randomly assigned to receive active high-frequency or sham tRNS targeted at bilateral inferior frontal cortices. Each group completed tests of facial identity perception, facial happiness perception and facial anger perception. These tasks were completed before and after stimulation. The results showed that, compared to the sham group, the active tRNS group showed greater gains in performance after stimulation in anger perception (relative to performance before stimulation). The same tRNS stimulation did not significantly change performance on the two other face perception tasks assessing facial identity and facial happiness perception. Examination of how inter-individual variability related to changes in anger perception following tRNS indicated that the degree of performance change in anger perception following active tRNS to inferior frontal cortex was predicted by baseline ability and gender of older adult participants. The findings suggest that high frequency tRNS may be a potential tool to aid anger perception in typical aging, but flag that performance variability and gender may interact with stimulation leading to different outcomes. [ABSTRACT FROM AUTHOR]

Numerosity and duration are thought to share common magnitude-based mechanisms in brain regions including the right parietal and frontal cortices like the supplementary motor area, SMA. Numerosity and duration are, however, also different in several intrinsic features. For instance, in a quantification context, numerosity is known for being more automatically accessed than temporal events, and durations are by definition sequential whereas numerosity can be both sequential and simultaneous. Moreover, numerosity and duration processing diverge in terms of their neuronal correlates. Whether these observed neuronal specificities can be accounted for by differences in automaticity or presentation-mode is however not clear. To address this issue, we used brain stimulation (transcranial random noise stimulation, tRNS) to the right parietal cortex or the SMA combined with experimental stimuli differing in their level of automaticity (numerosity and duration) and presentation mode (sequential or simultaneous). Compared to a no stimulation group, performance changed in duration but not in numerosity categorisation following right parietal but not SMA stimulation. These results indicate that the right parietal cortex is critical for duration processing, and suggest that tRNS has a stronger effect on less automatic processes such as duration. [ABSTRACT FROM AUTHOR]

Transcranial electrical stimulation (tES), including transcranial direct and alternating current stimulation (tDCS, tACS) are non-invasive brain stimulation techniques increasingly used for modulation of central nervous system excitability in humans. Here we address methodological issues required for tES application. This review covers technical aspects of tES, as well as applications like exploration of brain physiology, modelling approaches, tES in cognitive neurosciences, and interventional approaches. It aims to help the reader to appropriately design and conduct studies involving these brain stimulation techniques, understand limitations and avoid shortcomings, which might hamper the scientific rigor and potential applications in the clinical domain. [ABSTRACT FROM AUTHOR]

Objective The goals of this work are to report data regarding a large number of stimulation sessions and to use model analyses to explain the similarities or differences in the sensations induced by different parameters of tES application. Methods We analysed sensation data relative to 693 different tES sessions. In particular, we studied the effects on sensations induced by different types of current, categories of polarity and frequency, different timing, levels of current density and intensity, different electrode sizes and different electrode locations (areas). Results The application of random or fixed alternating current stimulation (i.e., tRNS and tACS) over the scalp induced less sensation compared with transcranial direct current stimulation (tDCS), regardless of the application parameters. Moreover, anodal tDCS induced more annoyance in comparison to other tES. Additionally, larger electrodes induced stronger sensations compared with smaller electrodes, and higher intensities were more strongly perceived. Timing of stimulation, montage and current density did not influence sensations perception. The analyses demonstrated that the induced sensations could be clustered on the basis of the type of somatosensory system activated. Finally and most important no adverse events were reported. Conclusion Induced sensations are modulated by electrode size and intensity and mainly pertain to the cutaneous receptor activity of the somatosensory system. Moreover, the procedure currently used to perform placebo stimulation may not be totally effective when compared with anodal tDCS. Significance The reported observations enrich the literature regarding the safety aspects of tES, confirming that it is a painless and safe technique. [ABSTRACT FROM AUTHOR]

Abstract: Background: Transcranial electric stimulation (tES) protocols are able to induce neuromodulation, offering important insights to focus and constrain theories of the relationship between brain and behavior. Previous studies have shown that different types of tES (i.e., direct current stimulation – tDCS, and random noise stimulation – tRNS) induce different facilitatory behavioral effects. However to date is not clear which is the optimal timing to apply tES in relation to the induction of robust facilitatory effects. Objective/hypothesis: The goal of this work was to investigate how different types of tES (tDCS and tRNS) can modulate behavioral performance in the healthy adult brain in relation to their timing of application. We applied tES protocols before (offline) or during (online) the execution of a visual perceptual learning (PL) task. PL is a form of implicit memory that is characterized by an improvement in sensory discrimination after repeated exposure to a particular type of stimulus and is considered a manifestation of neural plasticity. Our aim was to understand if the timing of tES is critical for the induction of differential neuromodulatory effects in the primary visual cortex (V1). Methods: We applied high-frequency tRNS, anodal tDCS and sham tDCS on V1 before or during the execution of an orientation discrimination task. The experimental design was between subjects and performance was measured in terms of d' values. Results: The ideal timing of application varied depending on the stimulation type. tRNS facilitated task performance only when it was applied during task execution, whereas anodal tDCS induced a larger facilitation if it was applied before task execution. Conclusion: The main result of this study is the finding that the timing of identical tES protocols yields opposite effects on performance. These results provide important guidelines for designing neuromodulation induction protocols and highlight the different optimal timing of the two excitatory techniques. [Copyright &y& Elsevier]

• Duration-tuned neural populations in the right SMG play a role in time perception. • Adaptation can elicit aftereffects in the perceived duration of time intervals. • hf-tRNS revealed the causal role of the right SMG in subjective experience of time. Neural populations in the supramarginal gyrus (SMG) of the right hemisphere have been shown to be involved in processing the subjective experience of time, particularly because of their selectivity to specific temporal durations. To directly investigate this relationship, we applied high-frequency transcranial Random Noise Stimulation (hf-tRNS) on the right SMG during a duration judgment task: 24 participants were required to judge the duration of a test visual stimulus (350, 450, 550, 650 ms) as shorter or longer than the duration of a reference auditory stimulus (500 ms). In half of the trials this procedure was preceded by a visual adaptation paradigm, used as a tool to manipulate the subjective experience of time: for 12 participants the adaptor was shorter than the test (250 ms), and for 12 participants it was longer than the test (750 ms). All participants performed an online hf-tRNS session and a sham control session. For each participant and for each condition, the Point of Subjective Equality (PSE) was calculated and results revealed an expected negative aftereffect in the group exposed to a longer adaptor. Moreover, hf-tRNS modulated participants' performance with respect to sham, confirming the involvement of the right SMG in temporal experience. Importantly, only in the group exposed to the longer adaptor, PSE values were higher during stimulation than during sham, only after the adaptation procedure (no difference emerged in trials without adaptation). This pattern of results confirms recent neuroimaging findings, and adds a direct evidence of the causal role of this area in subjective time experience. [ABSTRACT FROM AUTHOR]