Stimulation Of dlPFC Research Articles

Single session tDCS over the left DLPFC disrupts interference processing

Whether single session tDCS can impact upon cognition in healthy subjects is currently a heated debate against the background of inconsistent results. In view of the current methodological discussion concerning tDCS we developed an alternative approach to measure effects of single session tDCS on the Stroop task. The left DLPFC was stimulated in a pre-post design using a new electrode set-up (a 9 cm2 electrode was placed over the left DLPFC while a 35 cm2 was placed over the parieto-occipital cortex) contrasting anodal versus cathodal stimulation. The Stroop task was optimized concerning confounding variables that were not controlled in previous attempts to measure the effects of single-session tDCS on the Stroop task. In our sample of N = 32 healthy students we observed a significant single session tDCS effect on the Stroop effect in the error data as in our study cathodal stimulation as compared to anodal stimulation of the left DLPFC disrupted interference processing. This result confirms previous studies suggesting that neuromodulation of the left DLPFC impacts interference processing. Single-session tDCS can impact upon cognitive processes. A rigorous methodical approach is emphasized as the effects seem to be only of small to medium size.

Food craving, food choice and consumption: The role of impulsivity and sham-controlled tDCS stimulation of the right dlPFC

BackgroundImpulsivity has been found to be associated with overeating and obesity. Transcranial direct current stimulation (tDCS) may enhance inhibitory control while reducing food craving and intake. Thus, the aim of the present study was to investigate whether tDCS stimulation modifies food choice, craving and consumption as a function of trait impulsivity. MethodsForty-two predominantly healthy-weight women received active tDCS stimulation to the right dorsolateral prefrontal cortex and sham stimulation in a within participant design. Trait impulsivity was measured with a short form of the Barratt Impulsiveness Scale. Participants completed a computerized food-choice task, during which their mouse movements were traced. Current food craving was measured by a modified version of the Food Cravings Questionnaire-State as well as by desire to eat ratings for food pictures. Food intake was measured in a taste test. ResultsThere were no tDCS effects on any of the dependent variables. Trait impulsivity (and non-planning impulsivity in particular) was positively associated with higher calorie intake in the taste test, irrespective of tDCS stimulation. ConclusionThe current findings question the efficacy of single-session tDCS stimulation of the right dLPFC to reduce food craving, high caloric food choice and calorie intake in non-selected, predominantly healthy weight women. However, they do support the idea that trait impulsivity is related to overeating and, therefore, may be a risk factor for obesity. Future research needs to specify which appetitive behaviors can be modulated by brain stimulation and which populations might profit from it the most.

Transcranial Direct Current Stimulation Modulates Neuronal Networks in Attention Deficit Hyperactivity Disorder.

Anodal transcranial direct current stimulation (tDCS) of the prefrontal cortex has been repeatedly shown to improve working memory (WM). Since patients with attention deficit hyperactivity disorder (ADHD) are characterized by both underactivation of the prefrontal cortex and deficits in WM, the modulation of prefrontal activity with tDCS in ADHD patients may increase their WM performance as well as improve the activation and connectivity of the WM network. In the present study, this hypothesis was tested using a double-blind sham-controlled experimental design. After randomization, sixteen adolescents with ADHD underwent either anodal tDCS over the left dorsolateral prefrontal cortex (DLPFC, 1mA, 20min) or sham stimulation with simultaneous fMRI during n-back WM task. Both in one-back and two-back conditions, tDCS led to a greater activation (compared with sham stimulation) of the left DLPFC (under the electrode), left premotor cortex, left supplementary motor cortex, and precuneus. The effects of tDCS were long-lasting and influenced resting state functional connectivity even 20min after the stimulation, with patterns of strengthened DLPFC connectivity after tDCS outlining the WM network. In summary, anodal tDCS caused increased neuronal activation and connectivity, not only in the brain area under the stimulating electrode (i.e. left DLPFC) but also in other, more remote brain regions. Because of moderate behavioral effects of tDCS, the significance of this technique for ADHD treatment has to be investigated in further studies.

The efficacy of repetitive transcranial magnetic stimulation of left DLPFC with personalized targeting in major depression: preliminary results of pseudo-randomised study

The efficacy of repetitive transcranial magnetic stimulation of left DLPFC with personalized targeting in major depression: preliminary results of pseudo-randomised study

Neural correlates of trait resiliency: Evidence from electrical stimulation of the dorsolateral prefrontal cortex (dLPFC) and orbitofrontal cortex (OFC)

The topic of trait resiliency has recently been studied in many fields including personality psychology, clinical psychology and health sciences. Neuroimaging studies show some regions in the prefrontal cortex that are involved in resilience and coping behaviour. This study was primarily aimed to examine the effectiveness of transcranial direct current stimulation (tDCS) on level of trait resiliency of participants. Eighty students were randomly assigned into four groups. Each group completed the Conner-Davidson Resilience Scale (CD-RISC) once before brain stimulation and once 5min after receiving electrical brain stimulation for 15min with 1mA current intensity. Each group underwent a specific tDCS montage and results showed that anodal tDCS over the left dLPFC concurrently with cathode tDCS over the right dLPFC (Experiment 1) as well as anodal stimulation of the left dLPFC and cathodal stimulation of the right OFC (Experiment 2) led to an increase in the level of trait resiliency of participants. Results also showed a larger effect size for experiment 2. The findings of the present study implicate the involvement of the PFC regions in trait resiliency, especially in term of interaction of the dLPFC and the OFC regions in trait resiliency suggesting neural correlates underlying trait resiliency.

High-definition tDCS alters impulsivity in a baseline-dependent manner

In intertemporal choice (ITC), people discount future rewards in proportion to the time delay until reward receipt. Despite recent non-invasive brain stimulation studies suggesting a general causal link between dorsolateral prefrontal cortex (dlPFC) activity and ITC impulsivity, results regarding the functional specificity of dlPFC are mixed. We used high-definition transcranial direct current stimulation (HD-tDCS) to map changes in causal impulsivity through bi-directional modulation of left and right dlPFC during ITC. Model-free and model-based analyses demonstrated that anodal and cathodal stimulation of left dlPFC, but not right dlPFC, decreased and increased impulsivity, respectively. Critically, an individual differences analysis revealed that modulation of impulsivity was contingent on participants' baseline impulsivity. Overall, our results might reconcile the discrepancies in the existing literature and suggest a baseline-dependent role for left dlPFC during ITC.

Effects of transcranial direct current stimulation (tDCS) on binge eating disorder.

To investigate the effect of transcranial direct current stimulation (tDCS) on food craving, intake, binge eating desire, and binge eating frequency in individuals with binge eating disorder (BED). N = 30 adults with BED or subthreshold BED received a 20-min 2 milliampere (mA) session of tDCS targeting the dorsolateral prefrontal cortex (DLPFC; anode right/cathode left) and a sham session. Food image ratings assessed food craving, a laboratory eating test assessed food intake, and an electronic diary recorded binge variables. tDCS versus sham decreased craving for sweets, savory proteins, and an all-foods category, with strongest reductions in men (p < 0.05). tDCS also decreased total and preferred food intake by 11 and 17.5%, regardless of sex (p < 0.05), and reduced desire to binge eat in men on the day of real tDCS administration (p < 0.05). The reductions in craving and food intake were predicted by eating less frequently for reward motives, and greater intent to restrict calories, respectively. This proof of concept study is the first to find ameliorating effects of tDCS in BED. Stimulation of the right DLPFC suggests that enhanced cognitive control and/or decreased need for reward may be possible functional mechanisms. The results support investigation of repeated tDCS as a safe and noninvasive treatment adjunct for BED. © 2016 Wiley Periodicals, Inc.(Int J Eat Disord 2016; 49:930-936).

Electrically stimulating prefrontal cortex at retrieval improves recollection accuracy

Neuroimaging and brain damage studies suggest that dorsolateral prefrontal cortex (dlPFC) is involved in the cognitive control of episodic recollection. If dlPFC is causally involved in retrieval, then transcranial direct current stimulation (tDCS) of this brain region should increase recollection accuracy, especially when recollection is difficult and requires cognitive control. Here, we report the first brain stimulation experiment to directly test this hypothesis. We administered tDCS to dlPFC immediately after studying to-be-learned material but just prior to recollection testing, thereby targeting retrieval processes. We found that stimulation of dlPFC significantly increased recollection accuracy, relative to a no-stimulation sham condition and also relative to active stimulation of a comparison region in left parietal cortex. There was no significant difference in the size of this increase between hemispheres. Moreover, these dlPFC stimulation effects were behaviorally selective, increasing accuracy only when participants needed to recollect difficult information. Electrically stimulating dlPFC allowed people to more accurately recollect specific details of their experiences, demonstrating a causal role of dlPFC in the retrieval of episodic memories.

Epidural Cortical Stimulation of the Left DLPFC Leads to Dose-Dependent Enhancement of Working Memory in Patients with MDD

Background: Cognitive deficits are common across neuropsychiatric disorders, and a primary cause of functional disability. Nevertheless, clinicians have limited therapeutic options to facilitate cognitive enhancement, particularly of executive functions. We present results from a multicenter clinical trial of epidural cortical stimulation in patients with Major Depressive Disorder (MDD). The initial dose determination algorithm revealed acute dose-dependent facilitation of working memory function, suggesting specific therapeutic targets for device-based interventions. Methods: Ten patients with recurrent MDD without psychotic features were enrolled. Electrodes were surgically implanted in the left DLPFC. In order to determine the stimulation parameters, an algorithm was used to assess changes in working memory, mood and anxiety as a function of parametric variations in current amplitude. The Paced Visual Serial Addition Task was used to assess working memory, and Visual Analogue Scales for “Sadness” and “Anxiety”. Data were analyzed using repeated measures ANOVAs. Results: Patients tolerated the intervention well without significant side-effects. We observed a statistically significant relationship between current amplitude and working memory performance (p¼0.020) and reaction times (p¼0.035): higher current led to improved performance and reduced reaction times. We observed a nonsignificant trend for “sadness” and “anxiety”: higher current led to reduced scores for both. Conclusion: These data highlight the relevance of the left DLPFC as a therapeutic target for cognitive enhancement in neuropsychiatric populations. In addition, it confirms the capacity of brain stimulation to improve executive function in compromised patients. Similar strategies may be effective in otherclinical populations with compromised cognition, possibly with noninvasive interventions.

The Role of rTMS in the Treatment of Psychiatric Disorders Other than Major Depression

Repetitive transcranial magnetic stimulation (rTMS) offers a noninvasive, safe, and well-toleratedmethodofneuromodulation.WereviewedexistingliteraturecoveringrTMStreatment of posttraumatic stress disorder (PTSD), schizophrenia, dementia, bipolar disorder, obsessive-compulsive disorder (OCD), autism spectrum disorder (ASD), and attention-deficit/hyperactivity disorder (ADHD). Data for PTSD suggest the right dorsolateral prefrontal cortex may be a potential treatment site. rTMS in schizophrenia suggests high-frequency stimulation of the left DLPFC may have some benefit for negative symptoms, and low-frequency stimulation of the primary auditory cortex may assist with auditory hallucinations. The role of rTMS in the diagnosis and treatment of dementia is promising, but further studies are needed. Data for bipolar disorder are inconsistent across the spectrum of mood states. Treatment of OCD by stimulation of the supplementary motor area may have promise. Data are lacking regarding use of rTMS for ASD or ADHD to draw definitive conclusions. [ Psychiatr Ann . 2014; 44(6):293–298.]

Insight facilitation with add-on tDCS in schizophrenia

Impaired insight in schizophrenia patients has been linked with prefrontal deficits. In this open-label study, we examined for potential insight facilitation effects of add-on tDCS (with anodal stimulation of left DLPFC and cathodal stimulation over left temporo-parietal junction) in schizophrenia patients (N=21) with persistent auditory hallucinations despite adequate antipsychotic treatment. Following tDCS, there was a significant improvement in insight with concurrent significant reduction in auditory hallucination severity. Improvement in insight correlated significantly with improvement in severity of auditory hallucinations. These findings suggest improvement of insight with add-on tDCS in schizophrenia with persistent auditory hallucinations.

Frontal and Parietal Contributions to Probabilistic Association Learning

Neuroimaging studies have shown both dorsolateral prefrontal (DLPFC) and inferior parietal cortex (iPARC) activation during probabilistic association learning. Whether these cortical brain regions are necessary for probabilistic association learning is presently unknown. Participants' ability to acquire probabilistic associations was assessed during disruptive 1 Hz repetitive transcranial magnetic stimulation (rTMS) of the left DLPFC, left iPARC, and sham using a crossover single-blind design. On subsequent sessions, performance improved relative to baseline except during DLPFC rTMS that disrupted the early acquisition beneficial effect of prior exposure. A second experiment examining rTMS effects on task-naive participants showed that neither DLPFC rTMS nor sham influenced naive acquisition of probabilistic associations. A third experiment examining consecutive administration of the probabilistic association learning test revealed early trial interference from previous exposure to different probability schedules. These experiments, showing disrupted acquisition of probabilistic associations by rTMS only during subsequent sessions with an intervening night's sleep, suggest that the DLPFC may facilitate early access to learned strategies or prior task-related memories via consolidation. Although neuroimaging studies implicate DLPFC and iPARC in probabilistic association learning, the present findings suggest that early acquisition of the probabilistic cue-outcome associations in task-naive participants is not dependent on either region.