Non-linear effects of transcranial direct current stimulation as a function of individual baseline performance: Evidence from biparietal tDCS influence on lateralized attention bias (original) (raw)
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The Uncertain Outcome of Prefrontal tDCS
Brain Stimulation, 2014
Background: Transcranial direct current stimulation (tDCS) is increasingly used in research and clinical settings, and the dorsolateral prefrontal cortex (DLPFC) is often chosen as a target for stimulation. While numerous studies report modulation of cognitive abilities following DLPFC stimulation, the wide array of cognitive functions that can be modulated makes it difficult to predict its precise outcome. Objective: The present review aims at identifying and characterizing the various cognitive domains affected by tDCS over DLPFC. Methods: Articles using tDCS over DLPFC indexed in PubMed and published between January 2000 and January 2014 were included in the present review. Results: tDCS over DLPFC affects a wide array of cognitive functions, with sometimes apparent conflicting results. Conclusion: Prefrontal tDCS has the potential to modulate numerous cognitive functions simultaneously, but to properly interpret the results, a clear a priori hypothesis is necessary, careful technical consideration are mandatory, further insights into the neurobiological impact of tDCS are needed, and consideration should be given to the possibility that some behavioral effects may be partly explained by parallel modulation of related functions. is listed as an inventor on several issued and pending patents on the real-time integration of transcranial magnetic stimulation (TMS) with electroencephalography (EEG) and magnetic resonance imaging (MRI).
Brain Sciences, 2021
Transcranial direct current stimulation (tDCS) has become a valuable tool in cognitive neuroscience research as it enables causal inferences about neural underpinnings of cognition. However, studies using tDCS to modulate cognitive functions often yield inconsistent findings. Hence, there is an increasing interest in factors that may moderate the effects, one of which is the participants’ beliefs of the tDCS condition (i.e., real or sham) they received. Namely, whether participants’ correct guessing of sham condition may lead to false-positive tDCS effects. In this study, we aimed to explore if participants’ beliefs about received stimulation type (i.e., the success of blinding) impacted their task performance in tDCS experiments on associative (AM) and working memory (WM). We analyzed data from four within-subject, sham-controlled tDCS memory experiments (N = 83) to check if the correct end-of-study guess of sham condition moderated tDCS effects. We found no evidence that sham gues...
Hits and misses: leveraging tDCS to advance cognitive research
Frontiers in psychology, 2014
The popularity of non-invasive brain stimulation techniques in basic, commercial, and applied settings grew tremendously over the last decade. Here, we focus on one popular neurostimulation method: transcranial direct current stimulation (tDCS). Many assumptions regarding the outcomes of tDCS are based on the results of stimulating motor cortex. For instance, the primary motor cortex is predictably suppressed by cathodal tDCS or made more excitable by anodal tDCS. However, wide-ranging studies testing cognition provide more complex and sometimes paradoxical results that challenge this heuristic. Here, we first summarize successful efforts in applying tDCS to cognitive questions, with a focus on working memory (WM). These recent findings indicate that tDCS can result in cognitive task improvement or impairment regardless of stimulation site or direction of current flow. We then report WM and response inhibition studies that failed to replicate and/or extend previously reported effect...
tDCS polarity effects in motor and cognitive domains: a meta-analytical review
Experimental Brain Research, 2012
In vivo effects of transcranial direct current stimulation (tDCS) have attracted much attention nowadays as this area of research spreads to both the motor and cognitive domains. The common assumption is that the anode electrode causes an enhancement of cortical excitability during stimulation, which then lasts for a few minutes thereafter, while the cathode electrode generates the opposite effect, i.e., anodal-excitation and cathodalinhibition effects (AeCi). Yet, this dual-polarity effect has not been observed in all tDCS studies. Here, we conducted a meta-analytical review aimed to investigate the homogeneity/heterogeneity of the effect sizes of the AeCi dichotomy in both motor and cognitive functions. The AeCi effect was found to occur quite commonly with motor investigations and rarely in cognitive studies. When the anode electrode is applied over a non-motor area, in most cases, it will cause an excitation as measured by a relevant cognitive or perceptual task; however, the cathode electrode rarely causes an inhibition. We found homogeneity in motor studies and heterogeneity in cognitive studies with the electrode's polarity serving as a moderator that can explain the source of heterogeneity in cognitive studies. The lack of inhibitory cathodal effects might reflect compensation processes as cognitive functions are typically supported by rich brain networks. Further insights as to the polarity and domain interaction are offered, including subdivision to different classes of cognitive functions according to their likelihood of being affected by stimulation.
Individual Differences and State-Dependent Responses in Transcranial Direct Current Stimulation
Frontiers in human neuroscience, 2016
Transcranial direct current stimulation (tDCS) has been extensively used to examine whether neural activities can be selectively increased or decreased with manipulations of current polarity. Recently, the field has reevaluated the traditional anodal-increase and cathodal-decrease assumption due to the growing number of mixed findings that report the effects of the opposite directions. Therefore, the directionality of tDCS polarities and how it affects each individual still remain unclear. In this study, we used a visual working memory (VWM) paradigm and systematically manipulated tDCS polarities, types of different independent baseline measures, and task difficulty to investigate how these factors interact to determine the outcome effect of tDCS. We observed that only low-performers, as defined by their no-tDCS corsi block tapping (CBT) performance, persistently showed a decrement in VWM performance after anodal stimulation, whereas no tDCS effect was found when participants were d...
2016
Transcranial Direct Current Stimulation (tDCS) is a neuromodulation technique with promising results for enhancing cognitive information processes. So far, however, research has mainly focused on the effects of tDCS on cognitive control operations for non-emotional material. Therefore, our aim was to investigate the effects on cognitive control considering negative versus positive material. For this sham-controlled, withinsubjects study, we selected a homogeneous sample of twenty-five healthy participants. By using behavioral measures and event related potentials (ERP) as indexes, we aimed to investigate whether a single session of anodal tDCS of the left dorsolateral prefrontal cortex (DLPFC) would have specific effects in enhancing cognitive control for positive and negative valenced stimuli. After tDCS over the left DLPFC (and not sham control stimulation), we observed more negative N450 amplitudes along with faster reaction times when inhibiting a habitual response to happy compared to sad facial expressions. Gender did not influence the effects of tDCS on cognitive control for emotional information. In line with the Valence Theory of side-lateralized activity, this stimulation protocol might have led to a left dominant (relative to right) prefrontal cortical activity, resulting in augmented cognitive control specifically for positive relative to negative stimuli. To verify that tDCS induces effects that are in line with all aspects of the well known Valence Theory, future research should investigate the effects of tDCS over the left vs. right DLPFC on cognitive control for emotional information.
Brain Stimulation, 2014
Background: Acting coherently upon stimuli requires some kind of integration of stimulus and response features across various distinct cortical feature maps (one aspect of the binding problem). Although the process of feature binding proper seems rather automatic, recent studies revealed that the management of stimulus-response bindings is less efficient in populations with impaired cognitive-control processes. Objective: Here, we investigated whether the cognitive control of stimulus-response feature bindings ("event files") in healthy participants is affected by non-invasive brain stimulation (tDCS) of the dorsolateral prefrontal cortex (DLPFC)da main component of the cognitive-control network. Method: In different sessions, participants received anodal, cathodal, or sham tDCS (2 mA, 20 min) while performing an audio-visual event-file task assessing the creation and retrieval of stimulusestimulus and stimulus-response feature bindings. The general findings from this task indicate that performance suffers when some, but not all of the features are repeated (the so-called partial repetition cost). Results: Stimulation over the right, but not the left DLPFC reduced control of stimulus-response bindings and produced outcome patterns similar to those previously observed in autistic children, people with lower fluid intelligence, and older adults. Conclusions: This finding provides empirical support for a role of the right DLPFC in feature-binding management, which might consist in preventing the stimulus-induced activation of previously created, but now task-irrelevant, episodic bindings. From a methodological perspective, the finding may suggest that tDCS could be used as a temporary, reversible "brain lesion" generator in healthy subjects, enabling experimental investigation of how the brain works.
Transcranial Brain Stimulation in Cognitive Neuroscience Workshop Poster Abstracts, 2022
Substance-related and behavioural addictions have been associated with enhanced attentional bias to rewardassociated stimuli. In the current study, we explored the effect of Transcranial Direct Current Stimulation (tDCS) on reducing electrophysiological reflections of attentional orienting towards intrinsic rewardassociated stimuli. Sixty-five participants (19 men, 46 women) between 18 – 58 years old (M=24, SD = 6) were assigned to either tDCS or sham-tDCS intervention. The tDCs intervention consisted of 20 minutes of right frontal F4 anodal 2 mA stimulation, with the cathode at site F3 (left frontal). Before and after (sham-)intervention, participants performed a Visual Spatial Cueing (VSC) task, while EEG was recorded. In the VSC task, a cue indicates the most likely location (left or right) of the subsequent target to which a response is required. Our VSC adaptation included a neutral and food (intrinsic reward) context. The latter context was operationalized with target pictures depicting palatable food. Our results confirmed the validity of the paradigm in inducing attentional bias as indicated by faster responses to validly cued targets relative to invalidly cued targets. This effect was mirrored by an observed cue-associated Late Directing Attention Positivity Event Related Potential (LDAP ERP). In contrast to our hypothesis, attentional orienting (indexed by the LDAP) increased following tDCS relative to sham tDCS in the reward condition. Our results suggest that tDCS affects visuospatial attention via a mechanism other than shifting lateralization of frontal brain activity. One such alternative mechanism may involve tDCS associated enhancement of noradrenergic neurotransmission.
Cognitive Effects of Transcranial Direct Current Stimulation in Healthy and Clinical Populations
Journal of Ect, 2018
Transcranial direct current stimulation (tDCS) is a neuromodulatory approach that is affordable, safe, and well tolerated. This review article summarizes the research and clinically relevant findings from meta-analyses and studies investigating the cognitive effects of tDCS in healthy and clinical populations. We recapitulate findings from recent studies where cognitive performance paired with tDCS was compared with performance under placebo (sham stimulation) in single sessions and longitudinal designs where cognitive effects were evaluated following repeated sessions. In summary, the tDCS literature currently indicates that the effects of tDCS on cognitive measures are less robust and less predictable compared with the more consistent effects on motor outcomes. There is also a notable difference in the consistency of single-session and longitudinal designs. In single-session tDCS designs, there are small effects amid high variability confounded by individual differences and potential sham stimulation effects. In contrast, longitudinal studies provide more consistent benefits in healthy and clinical populations, particularly when tDCS is paired with a concurrent task. Yet, these studies are few in number, thereby impeding design optimization. While there is good evidence that tDCS can modulate cognitive functioning and potentially produce longer-term benefits, a major challenge to widespread translation of tDCS is the absence of a complete mechanistic account for observed effects. Significant future work is needed to identify a priori responders from nonresponders for every cognitive task and tDCS protocol.
Effects of tDCS Dosage on Working Memory in Healthy Participants
Background: Transcranial direct current stimulation (tDCS) has been found to improve working memory (WM) performance in healthy participants following a single session. However, results are mixed and the overall effect size is small. Interpretation of these results is confounded by heterogeneous study designs, including differences in tDCS dose (current intensity) and sham conditions used. Aims: We systematically investigated the effect of tDCS dose on working memory using behavioural and neurophysiological outcomes. Methods: In a single-blind parallel group design, 100 participants were randomised across five groups to receive 15 minutes of bifrontal tDCS at different current intensities (2mA, 1mA, and three sham tDCS conditions at 0.034mA, 0.016mA, or 0mA). EEG activity was acquired while participants performed a WM task prior to, during, and following tDCS. Response time, accuracy and an event-related EEG component (P3) were evaluated. Results: We found no significant differences...