Neural Correlates of Semantic Interference and Phonological Facilitation in Picture Naming: A Systematic Review and Coordinate-Based Meta-analysis.

Semantic interference (SI) and phonological facilitation (PF) effects occur when multiple representations are co-activated simultaneously in complex naming paradigms, manipulating the context in which word production is set. Although the behavioral consequences of these psycholinguistic effects are well-known, the involved brain structures are still controversial. This paper aims to provide a systematic review and a coordinate-based meta-analysis of the available functional neuroimaging studies investigating SI and PF in picture naming paradigms. The included studies were fMRI experiments on healthy subjects, employing paradigms in which co-activations of representations were obtained by manipulating the naming context using semantically or phonologically related items. We examined the principal methodological aspects of the included studies, emphasizing the existing commonalities and discrepancies across single investigations. We then performed an exploratory coordinate-based meta-analysis of the reported activation peaks of neural response related to SI and PF. Our results consolidated previous findings regarding the involvement of the left inferior frontal gyrus and the left middle temporal gyrus in SI and brought out the role of bilateral inferior parietal regions in PF.

Multimodal approaches supporting the diagnosis, prognosis and investigation of neural correlates of disorders of consciousness: A systematic review.

The limits of the standard, behaviour-based clinical assessment of patients with disorders of consciousness (DoC) prompted the employment of functional neuroimaging, neurometabolic, neurophysiological and neurostimulation techniques, to detect brain-based covert markers of awareness. However, uni-modal approaches, consisting in employing just one of those techniques, are usually not sufficient to provide an exhaustive exploration of the neural underpinnings of residual awareness. This systematic review aimed at collecting the evidence from studies employing a multimodal approach, that is, combining more instruments to complement DoC diagnosis, prognosis and better investigating their neural correlates. Following the PRISMA guidelines, records from PubMed, EMBASE and Scopus were screened to select peer-review original articles in which a multi-modal approach was used for the assessment of adult patients with a diagnosis of DoC. Ninety-two observational studies and 32 case reports or case series met the inclusion criteria. Results highlighted a diagnostic and prognostic advantage of multi-modal approaches that involve electroencephalography-based (EEG-based) measurements together with neuroimaging or neurometabolic data or with neurostimulation. Multimodal assessment deepened the knowledge on the neural networks underlying consciousness, by showing correlations between the integrity of the default mode network and the different clinical diagnosis of DoC. However, except for studies using transcranial magnetic stimulation combined with electroencephalography, the integration of more than one technique in most of the cases occurs without an a priori-designed multi-modal diagnostic approach. Our review supports the feasibility and underlines the advantages of a multimodal approach for the diagnosis, prognosis and for the investigation of neural correlates of DoCs.

State-dependent effectiveness of cathodal transcranial direct current stimulation on cortical excitability.

The extensive use of transcranial direct current stimulation (tDCS) in experimental and clinical settings does not correspond to an in-depth understanding of its underlying neurophysiological mechanisms. In previous studies, we employed an integrated system of Transcranial Magnetic Stimulation and Electroencephalography (TMS-EEG) to track the effect of tDCS on cortical excitability. At rest, anodal tDCS (a-tDCS) over the right Posterior Parietal Cortex (rPPC) elicits a widespread increase in cortical excitability. In contrast, cathodal tDCS (c-tDCS) fails to modulate cortical excitability, being indistinguishable from sham stimulation. Here we investigated whether an endogenous task-induced activation during stimulation might change this pattern, improving c-tDCS effectiveness in modulating cortical excitability. In Experiment 1, we tested whether performance in a Visuospatial Working Memory Task (VWMT) and a modified Posner Cueing Task (mPCT), involving rPPC, could be modulated by c-tDCS. Thirty-eight participants were involved in a two-session experiment receiving either c-tDCS or sham during tasks execution. In Experiment 2, we recruited sixteen novel participants who performed the same paradigm but underwent TMS-EEG recordings pre- and 10 min post- sham stimulation and c-tDCS. Behavioral results showed that c-tDCS significantly modulated mPCT performance compared to sham. At a neurophysiological level, c-tDCS significantly reduced cortical excitability in a frontoparietal network likely involved in task execution. Taken together, our results provide evidence of the state dependence of c-tDCS in modulating cortical excitability effectively. The conceptual and applicative implications are discussed.

Betting on Non-Invasive Brain Stimulation to Treat Gambling Disorder: A Systematic Review and Meta-Analysis.

Gambling disorder (GD) is a behavioral addiction that severely impacts individuals' functioning, leading to high socioeconomic costs. Non-invasive brain stimulation (NiBS) has received attention for treating psychiatric and neurological conditions in recent decades, but there is no recommendation for its use for GD. Therefore, this study aimed to systematically review and analyze the available literature to determine the effectiveness of NiBS in treating GD. Following the PRISMA guidelines, we screened four electronic databases up to July 2022 and selected relevant English-written original articles. We included ten papers in the systematic review and seven in the meta-analysis. As only two studies employed a sham-controlled design, the pre-post standardized mean change (SMCC) was computed as effect size only for real stimulation. The results showed a significant effect of NiBS in reducing craving scores (SMCC = -0.69; 95% CI = [-1.2, -0.2], p = 0.010). Moreover, considering the GD's frequent comorbidity with mood disorders, we ran an exploratory analysis of the effects of NiBS on depressive symptoms, which showed significant decreases in post-treatment scores (SMCC = -0.71; 95% CI = [-1.1, -0.3], p < 0.001). These results provide initial evidence for developing NiBS as a feasible therapy for GD symptoms but further comprehensive research is needed to validate these findings. The limitations of the available literature are critically discussed.

Inter-Individual Variability in tDCS Effects: A Narrative Review on the Contribution of Stable, Variable, and Contextual Factors.

Due to its safety, portability, and cheapness, transcranial direct current stimulation (tDCS) use largely increased in research and clinical settings. Despite tDCS's wide application, previous works pointed out inconsistent and low replicable results, sometimes leading to extreme conclusions about tDCS's ineffectiveness in modulating behavioral performance across cognitive domains. Traditionally, this variability has been linked to significant differences in the stimulation protocols across studies, including stimulation parameters, target regions, and electrodes montage. Here, we reviewed and discussed evidence of heterogeneity emerging at the intra-study level, namely inter-individual differences that may influence the response to tDCS within each study. This source of variability has been largely neglected by literature, being results mainly analyzed at the group level. Previous research, however, highlighted that only a half-or less-of studies' participants could be classified as responders, being affected by tDCS in the expected direction. Stable and variable inter-individual differences, such as morphological and genetic features vs. hormonal/exogenous substance consumption, partially account for this heterogeneity. Moreover, variability comes from experiments' contextual elements, such as participants' engagement/baseline capacity and individual task difficulty. We concluded that increasing knowledge on inter-dividual differences rather than undermining tDCS effectiveness could enhance protocols' efficiency and reproducibility.

Effectiveness of noninvasive brain stimulation in the treatment of anxiety disorders: a meta-analysis of sham or behaviour-controlled studies.

BACKGROUND: The possibility of using noninvasive brain stimulation to treat mental disorders has received considerable attention recently. Repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) are considered to be effective treatments for depressive symptoms. However, no treatment recommendation is currently available for anxiety disorders, suggesting that evidence is still limited. We conducted a systematic review of the literature and a quantitative analysis of the effectiveness of rTMS and tDCS in the treatment of anxiety disorders. METHODS: Following PRISMA guidelines, we screened 3 electronic databases up to the end of February 2020 for English-language, peer-reviewed articles that included the following: a clinical sample of patients with an anxiety disorder, the use of a noninvasive brain stimulation technique, the inclusion of a control condition, and pre/post scores on a validated questionnaire that measured symptoms of anxiety. RESULTS: Eleven papers met the inclusion criteria, comprising 154 participants assigned to a stimulation condition and 164 to a sham or control group. We calculated Hedge's g for scores on disorder-specific and general anxiety questionnaires before and after treatment to determine effect size, and we conducted 2 independent random-effects meta-analyses. Considering the well-known comorbidity between anxiety and depression, we ran a third meta-analysis analyzing outcomes for depression scores. Results showed a significant effect of noninvasive brain stimulation in reducing scores on disorder-specific and general anxiety questionnaires, as well as depressive symptoms, in the real stimulation compared to the control condition. LIMITATIONS: Few studies met the inclusion criteria; more evidence is needed to strengthen conclusions about the effectiveness of noninvasive brain stimulation in the treatment of anxiety disorders. CONCLUSION: Our findings showed that noninvasive brain stimulation reduced anxiety and depression scores compared to control conditions, suggesting that it can alleviate clinical symptoms in patients with anxiety disorders.

Exploring the time-course and the reference frames of adaptation to optical prisms and its aftereffects.

Prism adaptation (PA) is used to investigate visuo-motor plasticity and to rehabilitate the syndrome of Unilateral Spatial Neglect (USN). After PA, participants show aftereffects (AEs), contralateral to the side of the optical displacement in several tasks. This study explored the features of these AEs, specifically the "egocentric" versus "allocentric, object-based", reference frames involved, and their time course. In three experiments, healthy participants adapted to prismatic lenses inducing a horizontal displacement of the visual field. In Experiment #1, participants adapted to rightward displacing prisms. Four tasks were used requiring repeated pointings towards the participant's subjective egocentric straight-ahead, with the availability of proprioceptive or visual-proprioceptive signals, and, in some conditions, of an external allocentric visual frame (i.e., a rectangular paper sheet). Experiment #2 explored the role of the position of the allocentric frame, with AEs being tested by straight-ahead and frame bisection tasks, requiring pointing toward the external visual frame, placed in different positions of the working space. An egocentric visual proprioceptive task was administered after prism removal and after the execution of the allocentric tasks, to assess the effectiveness of the PA, as indexed by the AEs, and their persistence up to the end of the administration of the allocentric tasks. Experiment #3 differed from #2 in that participants adapted to leftward displacing lenses. Consistent with evidence from USN patients, in Experiment #1, in the egocentric tasks, AEs lasting up to 30 min after PA were found. In Experiment #2, AEs in "allocentric" tasks did not occur, regardless of frame position. Experiment #3 showed AEs in both the "egocentric" and the "allocentric" tasks, with the latter being minor in size. These findings illustrate that the spatial reference systems modulated by PA in extra-personal space primarily operate in spatial "egocentric" reference frames, with a comparatively minor and direction-specific role of "allocentric" frames.

Primary motor cortex and phonological recoding: A TMS-EMG study.

Since the 1960s, evidence from healthy participants and brain-damaged patients, neuroimaging and non-invasive brain stimulation studies has specified the neurofunctional architecture of the short-term memory (STM) system, supporting the temporary retention of a limited amount of verbal material. Auditory-verbal, later termed Phonological (Ph) STM or Phonological Loop, comprises two sub-components: i) the main storage system, the Phonological Short-Term Store (PhSTS), to which auditory verbal stimuli have direct access and where phonologically coded information is retained for a few seconds; ii) a Rehearsal Process (REH), which actively maintains the trace held in the PhSTS, preventing its decay and conveys visual verbal material to the PhSTS, after the process of Phonological Recoding (PhREC, or Grapheme-to-Phoneme Conversion) has taken place. PhREC converts visuo-verbal graphemic representations into phonological ones. The neural correlates of PhSTM include two discrete regions in the left hemisphere: the temporo-parietal junction (PhSTS) and the inferior frontal gyrus in the premotor cortex (REH). The neural basis of PhREC has been much less investigated. A few single case studies of patients made anarthric by focal or degenerative cortical damage, who show a pattern of impairment indicative of a deficit of PhREC, sparing the REH process, suggest that the primary motor cortex (M1) might be involved. To test this hypothesis in healthy participants with a neurophysiological approach, we measured the corticospinal excitability of M1, by means of Transcranial Magnetic Stimulation (TMS)-induced Motor Evoked Potentials (MEPs), during the execution of phonological judgements on auditorily vs. visually presented words (Experiment #1). Crucially, these phonological tasks involve REH, while PhREC is required only with visual presentation. Results show MEPs with larger amplitude when stimuli are presented visually. Task difficulty does not account for this difference and the result is specific for linguistic stimuli, indeed visual and auditory stimuli that cannot be verbalized lead to different behavioral and neurophysiological patterns (Experiment #2). The increase of corticospinal excitability when words are presented visually can be then interpreted as an indication of the involvement of M1 in PhREC. The present findings elucidate the neural correlates of PhREC, suggesting an involvement of the peripheral motor system in its activity.

Mind the stimulation site: Enhancing and diminishing sentence comprehension with anodal tDCS.

In a previous sham-controlled study, we showed the feasibility of increasing language comprehension in healthy participants by applying anodal transcranial direct current stimulation (atDCS) over the left inferior frontal gyrus (LIFG). In the present work, we present a follow-up experiment targeting with atDCS the left inferior parietal cortex (LIPC) while participants performed the same auditory comprehension task used in our previous experiment. Both neural sites (LIFG and LIPC) are crucial hubs of Baddeley's model of verbal short-term memory (vSTM). AtDCS over LIPC decreased accuracy as compared to sham and LIFG stimulation, suggesting the involvement of this area in sentence comprehension. Crucially, our results highlighted that applying tDCS over different hubs of the same neural network can lead to opposite behavioural results, with relevant implications from a clinical perspective.

Infant-directed speech as a simplified but not simple register: a longitudinal study of lexical and syntactic features.

Infant-directed speech (IDS) is a specific register that adults use to address infants, and it is characterised by prosodic exaggeration and lexical and syntactic simplification. Several authors have underlined that this simplified speech becomes more complex according to the infant's age. However, there is a lack of studies on lexical and syntactic modifications in Italian IDS during the first year of an infant's life. In the present study, 80 mother-infant dyads were longitudinally observed at 3, 6, 9, and 12 months during free-play interactions. Maternal vocal productions were subsequently coded. The results show an overall low lexical variability and syntactic complexity that identify speech to infants as a simplified register; however, the high occurrence of complex items and well-structured utterances suggests that IDS is not simple speech. Moreover, maternal IDS becomes more complex over time, but not linearly, with a maximum simplification in the second half of the first year.

Stimulating the ventrolateral prefrontal cortex (VLPFC) modulates frustration-induced aggression: A tDCS experiment.

BACKGROUND: The prefrontal cortex is crucial for top-down regulation of aggression, but the neural underpinnings of aggression are still poorly understood. Past research showed the transcranial direct current stimulation (tDCS) over the ventrolateral prefrontal cortex (VLPFC) modulates aggression following exposure to risk factors for aggression (e.g., social exclusion, violent media). Although frustration is a key risk factor for aggression, no study to date has examined the modulatory role of tDCS on frustration-induced aggression. OBJECTIVES: By exploring the VLPFC involvement in frustration-aggression link, we tested the hypothesis that the anodal tDCS over right and left VLPFC modulates frustration-induced aggression. We also explored whether tDCS interacts with gender to influence frustration-induced aggression. METHODS: 90 healthy participants (45 men) were randomly assigned to receive anodal or sham tDCS over the right or left VLPFC before being frustrated by an accomplice. To increase reliability, several tasks were used to measure aggression. RESULTS: We found that anodal tDCS over the left VLPFC, compared to sham stimulation, increased aggression. Unexpectedly, no main effect was found following tDCS of right VLPFC. However, we also found a significant interaction between gender and tDCS, showing that males were more aggressive than females following sham stimulation, but females became as aggressive as males following active tDCS. CONCLUSION: Overall, these results shed light on the neural basis of frustration-induced aggression, providing further evidence for the involvement of VLPFC in modulating aggressive responses, and on gender differences in aggression. Future research should further investigate the role of stimulating the VLPFC on frustration-induced aggression.

TMS-EEG approach unveils brain mechanisms underlying conscious and unconscious face perception.

BACKGROUND: Conscious perception of external stimuli has been related to recurrent activity in distributed cortical networks, although brain mechanisms controlling unconscious processing and stimuli access to conscious report need to be clarified. OBJECTIVE: This study aims at investigating modulations in cortical excitability related to conscious perception and unconscious processing of face stimuli with different visibility levels. METHODS: We used TMS-EEG over the right occipital face area (rOFA), or the right premotor cortex (rPMC) as control site, to measure cortical excitability during a backward masking paradigm with individually defined stimuli visibility. RESULTS: Event related potentials showed significant differences for faces compared to houses, and detected faces compared to missed ones, 200 ms post target onset. TMS over rOFA, but not over rPMC, triggered a relative positivity starting 150 ms post target when faces with high visibility were consciously reported. Moreover, rOFA TMS evoked differential responses for high versus low visible faces in conscious and unconscious processing at 290-390 and 180-240 ms, respectively. CONCLUSION: Results unveiled a causal link between rOFA excitability and late responses related to access to conscious perception, suggesting a critical role of recurrent activity, but distinct components, for consciously perceived stimuli and unconscious face processing.

Selective changes in moral judgment by noninvasive brain stimulation of the medial prefrontal cortex.

Multiple cortical networks intervene in moral judgment, among which the dorsolateral prefrontal cortex (DLPFC) and the medial prefrontal structures (medial PFC) emerged as two major territories, which have been traditionally attributed, respectively, to cognitive control and affective reactions. However, some recent theoretical and empirical accounts disputed this dualistic approach to moral evaluation. In the present study, to further assess the functional contribution of the medial PFC in moral judgment, we modulated its cortical excitability by means of transcranial direct current stimulation (tDCS) and tracked the change in response to different types of moral dilemmas, including switch-like and footbridge-like moral dilemmas, with and without personal involvement. One hundred participants (50 males) completed a questionnaire to assess the baseline levels of deontology. Next, participants were randomly assigned to receive anodal, sham, or cathodal tDCS over the medial prefrontal structures and then were asked to address a series of dilemmas. The results showed that participants who received anodal stimulation over the medial PFC provided more utilitarian responses to switch-like (but not footbridge-like) dilemmas than those who received cathodal tDCS. We also found that neurostimulation modulated the influence that deontology has on moral choices. Specifically, in the anodal tDCS group, participants' decisions were less likely to be influenced by their baseline levels of deontology compared with the sham or cathodal groups. Overall, our results seem to refute a functional role of the medial prefrontal structures purely restricted to affective reactions for moral dilemmas, providing new insights on the functional contribution of the medial PFC in moral judgment.

Modulation of negative emotions through anodal tDCS over the right ventrolateral prefrontal cortex.

Increasing evidence suggests that the right ventrolateral prefrontal cortex (rVLPFC) plays a critical role in emotion regulation, in particular concerning negative feelings. In the present research, we applied anodal transcranial direct current stimulation (tDCS) over the rVLPFC with a twofold purpose. First, we aimed at exploring the feasibility of modulating the subjective experience of emotions through tDCS in healthy participants. Second, we wanted to assess which specific emotion can be regulated (and which cannot) with this brain stimulation approach. We designed a double-blind, between-subjects, sham-controlled study in which 96 participants watched short video clips eliciting different emotions during anodal or sham tDCS over the rVLPFC. Emotional reactions to each video clip were assessed with self-report scales measuring eight basic emotions. Results showed that, in contrast to the sham condition, tDCS over the rVLPFC reduced the perceived extent of specific negative emotions, namely, fear, anxiety, and sadness, compared to other negative or positive feelings. Overall, these results support the role of rVLPFC in regulating negative emotions, mostly associated with the prevention of dangerous situations (i.e., fear, anxiety, and sadness).

Tracking the Effect of Cathodal Transcranial Direct Current Stimulation on Cortical Excitability and Connectivity by Means of TMS-EEG.

Transcranial direct current stimulation (tDCS) is increasingly used in both research and therapeutic settings, but its precise mechanisms remain largely unknown. At a neuronal level, tDCS modulates cortical excitability by shifting the resting membrane potential in a polarity-dependent way: anodal stimulation increases the spontaneous firing rate, while cathodal decreases it. However, the neurophysiological underpinnings of anodal/cathodal tDCS seem to be different, as well as their behavioral effect, in particular when high order areas are involved, compared to when motor or sensory brain areas are targeted. Previously, we investigated the effect of anodal tDCS on cortical excitability, by means of a combination of Transcranial Magnetic Stimulation (TMS) and Electroencephalography (EEG). Results showed a diffuse rise of cortical excitability in a bilateral fronto-parietal network. In the present study, we tested, with the same paradigm, the effect of cathodal tDCS. Single pulse TMS was delivered over the left posterior parietal cortex (PPC), before, during, and after 10 min of cathodal or sham tDCS over the right PPC, while recording HD-EEG. Indexes of global and local cortical excitability were obtained both at sensors and cortical sources level. At sensors, global and local mean field power (GMFP and LMFP) were computed for three temporal windows (0-50, 50-100, and 100-150 ms), on all channels (GMFP), and in four different clusters of electrodes (LMFP, left and right, in frontal and parietal regions). After source reconstruction, Significant Current Density was computed at the global level, and for four Broadmann's areas (left/right BA 6 and 7). Both sensors and cortical sources results converge in showing no differences during and after cathodal tDCS compared to pre-stimulation sessions, both at global and local level. The same holds for sham tDCS. These data highlight an asymmetric impact of anodal and cathodal stimulation on cortical excitability, with a diffuse effect of anodal and no effect of cathodal tDCS over the parietal cortex. These results are consistent with the current literature: while anodal-excitatory and cathodal-inhibitory effects are well-established in the sensory and motor domains, both at physiological and behavioral levels, results for cathodal stimulation are more controversial for modulation of exitability of higher order areas.

Goal Achievement Failure Drives Corticospinal Modulation in Promotion and Prevention Contexts.

When making decisions, people are typically differently sensitive to gains and losses according to the motivational context in which the choice is performed. As hypothesized by Regulatory Focus Theory (RFT), indeed, goals are supposed to change in relation to the set of possible outcomes. In particular, in a promotion context, the goal is achieving the maximal gain, whereas in a prevention context it turns into avoiding the greatest loss. We explored the neurophysiological counterpart of this phenomenon, by applying Transcranial Magnetic Stimulation (TMS) and recording the motor evoked potentials (MEPs) in participants taking part in an economic game, in which they observed actions conveying different goal attainment levels, framed in different motivational contexts. More than the actual value of the economic exchange involved in the game, what affected motor cortex excitability was the goal attainment failure, corresponding to not achieving the maximal payoff in a promotion context and not avoiding the greatest snatch in a prevention context. Therefore, the results provide support for the key predictions of RFT, identifying a neural signature for the goal attainment failure.

Cognitive Enhancement Induced by Anodal tDCS Drives Circuit-Specific Cortical Plasticity.

Increasing evidence shows that anodal transcranial direct current stimulation (tDCS) enhances cognitive performance in healthy and clinical population. Such facilitation is supposed to be linked to plastic changes at relevant cortical sites. However, direct electrophysiological evidence for this causal relationship is still missing. Here, we show that cognitive enhancement occurring in healthy human subjects during anodal tDCS is affected by ongoing brain activity, increasing cortical excitability of task-related brain networks only, as directly measured by Transcranial Magnetic Stimulation combined with electroencephalography (TMS-EEG). Specifically, TMS-EEG recordings were performed before and after anodal tDCS coupled with a verbal fluency task. To control for effects of tDCS protocol and TMS target location, 3 conditions were assessed: anodal/sham tDCS with TMS over left premotor cortex, anodal tDCS with TMS over left posterior parietal cortex. Modulation of cortical excitability occurred only at left Brodmann's areas 6, 44, and 45, a key network for language production, after anodal tDCS and TMS over the premotor cortex, and was positively correlated to the degree of cognitive enhancement. Our results suggest that anodal tDCS specifically affects task-related functional networks active while delivering stimulation, and this boost of specific cortical circuits is correlated to the observed cognitive enhancement.

Anodal transcranial direct current stimulation over left inferior frontal gyrus enhances sentence comprehension.

We tested the possibility of enhancing natural language comprehension through the application of anodal tDCS (a-tDCS) over the left inferior frontal gyrus, a key region for verbal short-term memory and language comprehension. We designed a between subjects sham- and task-controlled study. During tDCS stimulation, participants performed a sentence to picture matching task in which targets were sentences with different load on short-term memory. Regardless of load on short-term memory, the Anodal group performed significantly better than the Sham group, thus providing evidence that a-tDCS over LIFG enhances natural language comprehension. To our knowledge, we apply for the first time tDCS to boost sentence comprehension. This result is of special interest also from a clinical perspective: applying a-tDCS in patients manifesting problems at the sentence level due to brain damage could enhance the effects of behavioral rehabilitation procedures aimed to improve language comprehension.

What is difficult for you can be easy for me. Effects of increasing individual task demand on prefrontal lateralization: A tDCS study.

Neuroimaging studies suggest that the increment of the cognitive load associated with a specific task may induce the recruitment of a more bilateral brain network. In most studies, however, task demand has been manipulated in a static and pre-specified way, regardless of individual cognitive resources. Here we implemented a new paradigm based on a pre-experimental assessment to set up subject-specific levels of task demand and applied tDCS (transcranial direct current stimulation) to assess each hemisphere involvement in task performance. 24 young participants performed a digit span backward (DSB, complex cognitive function) and a paced finger tapping task (pFT, basic motor function) at 3 levels of subject-specific task demand ("low" 5/5 correct answers, "medium" 3/5, "high" 1/5). Anodal tDCS (20min, 1.5mA) was delivered through a target electrode (5 × 5cm) positioned to stimulate both the inferior frontal gyrus and the primary motor area over left and right hemisphere and in sham condition in three different days. A 3 (left, right, sham) × 3 (low, medium, high) mixed-model with random intercept for subjects was run with R software. As expected, in both tasks accuracy decreased with the increment of subject-specific task demand. Moreover, a significant interaction between type of stimulation and subject-specific task demand was found for the reaction times recorded during the DSB and for the accuracy in the pFT: in the most demanding conditions, right anodal tDCS significantly interfered with behavioural performance. Our results suggest that hemispheric lateralization is modulated by the subject-specific level of task demand and this modulation is not task-specific.