Dorsolateral Prefrontal Cortex Groups Research Articles

Effects of Transcranial Direct Current Stimulation Targeting Dorsolateral Prefrontal Cortex and Orbitofrontal Cortex on Somatic Symptoms in Patients With Major Depressive Disorder: A Randomized, Double-Blind, Controlled Clinical Trial.

There is a lack of research on transcranial direct current stimulation (tDCS) for the treatment of somatic symptoms in major depressive disorder (MDD) and the suitable stimulating brain region. We investigated the efficacy of tDCS targeting the dorsolateral prefrontal cortex (DLPFC) versus orbitofrontal cortex (OFC) on depressive somatic symptoms and somatic anxiety in patients with MDD and aimed to identify the appropriate stimulating brain regions. In this randomized, double-blind, sham-controlled study, a total of 70 patients diagnosed with MDD were randomly allocated into DLPFC group, OFC group, and Sham group. Subjects participated in 2 weeks of 10 primary interventions and subsequently 2-week maintenance interventions weekly (20 min, 2 mA). The DLPFC group showed a more significant improvement in somatic symptoms compared to the Sham group at week 2. At the maintenance and follow-up stages, the DLPFC group outperformed the Sham and OFC groups, but the difference with the Sham group was not significant. Neither active group demonstrated superiority over the Sham group in improving depression and anxiety. In conclusion, the tDCS targeting DLPFC may be a potentially effective therapeutic target for alleviating somatic symptoms in patients with MDD.

Effect of transcranial direct current stimulation with concurrent cognitive performance targeting posterior parietal cortex vs prefrontal cortex on working memory in schizophrenia: a randomized clinical trial

Working memory deficits are linked to irregularities in the dorsolateral prefrontal cortex (DLPFC) and the posterior parietal cortex (PPC) in schizophrenia, effective intervention strategies are lacking. We evaluated the differential efficacy and underlying neuromechanisms of targeting transcranial direct current stimulation (tDCS) at the DLPFC and the PPC with concurrent cognitive performance for working memory in schizophrenia. In a randomized and double-blind clinical trial, sixty clinically stable schizophrenic patients with below-average working memory were randomly assigned to active DLPFC, active PPC, and sham tDCS groups. Two sessions of tDCS during N-back task were delivered daily for five days. The primary outcome was changes in spatial span test scores from baseline to week 1. The secondary outcomes included changes in scores of color delay-estimation task, other cognitive tasks, and mismatch negativity (biomarker of N-methyl-d-aspartate receptor functioning). Compared with the active DLPFC group, the active PPC group demonstrated significantly greater improvement in spatial span test scores (p = 0.008, d = 0.94) and an augmentation in color delay-estimation task capacity at week 1; the latter sustained to week 2. Compared with the sham tDCS group, the active PPC group did not show a significant improvement in spatial span test scores at week 1 and 2; however, significant enhancement was observed in their color delay-estimation task capacity at week 2. Additionally, mismatch negativity amplitude was enhanced, and changes in theta band measures were positively correlated with working memory improvement in the active PPC group, while no such correlations were observed in the active DLPFC group or the sham tDCS group. Our results suggest that tDCS targeting the PPC relative to the DLPFC during concurrent cognitive performance may improve working memory in schizophrenia, meriting further investigation. The improvement in working memory appears to be linked to enhanced N-methyl-d-aspartate receptor functioning.

Site Dependency of Anodal Transcranial Direct-Current Stimulation on Reaction Time and Transfer of Learning during a Sequential Visual Isometric Pinch Task.

Considering the advantages of brain stimulation techniques in detecting the role of different areas of the brain in human sensorimotor behaviors, we used anodal transcranial direct-current stimulation (a-tDCS) over three different brain sites of the frontoparietal cortex (FPC) in healthy participants to elucidate the role of these three brain areas of the FPC on reaction time (RT) during a sequential visual isometric pinch task (SVIPT). We also aimed to assess if the stimulation of these cortical sites affects the transfer of learning during SVIPT. A total of 48 right-handed healthy participants were randomly assigned to one of the four a-tDCS groups: (1) left primary motor cortex (M1), (2) left dorsolateral prefrontal cortex (DLPFC), (3) left posterior parietal cortex (PPC), and (4) sham. A-tDCS (0.3 mA, 20 min) was applied concurrently with the SVIPT, in which the participants precisely controlled their forces to reach seven different target forces from 10 to 40% of the maximum voluntary contraction (MVC) presented on a computer screen with the right dominant hand. Four test blocks were randomly performed at the baseline and 15 min after the intervention, including sequence and random blocks with either hand. Our results showed significant elongations in the ratio of RTs between the M1 and sham groups in the sequence blocks of both the right-trained and left-untrained hands. No significant differences were found between the DLPFC and sham groups and the PPC and sham groups in RT measurements within the SVIPT. Our findings suggest that RT improvement within implicit learning of an SVIPT is not mediated by single-session a-tDCS over M1, DLPFC, or PPC. Further research is needed to understand the optimal characteristics of tDCS and stimulation sites to modulate reaction time in a precision control task such as an SVIPT.

Frontal two-electrode transcranial direct current stimulation protocols may not affect performance on a combined flanker Go/No-Go task

Transcranial direct current stimulation (tDCS) has been tested to modulate cognitive control or response inhibition using various electrode montages. However, electrode montages and current polarities have not been systematically compared when examining tDCS effects on cognitive control and response inhibition. In this randomized, sham-controlled study, 38 healthy volunteers were randomly grouped into receiving one session of sham, anodal, and cathodal each in an electrode montage that targeted either the dorsolateral prefrontal cortex (DLPFC) or the fronto-medial (FM) region. Participants performed a combined flanker Go/No-Go task during stimulation. No effect of tDCS was found in the DLPFC and FM groups neither using anodal nor cathodal stimulation. No major adverse effects of tDCS were identified using either montage or stimulation type and the two groups did not differ in terms of the reported sensations. The present study suggests that single-session tDCS delivered in two two-electrode montages might not affect cognitive control or response inhibition, despite using widely popular stimulation parameters. This is in line with the heterogeneous findings in the field and calls for further systematic research to exclude less reliable methods from those with more pronounced effects, identify the determinants of responsiveness, and develop optimal ways to utilize this technique.

Depressive symptom dimensions predict the treatment effect of repetitive transcranial magnetic stimulation for post-stroke depression

ObjectiveRepetitive transcranial magnetic stimulation (rTMS) has attracted considerable attention because of its non-invasiveness, minimal side effects, and treatment efficacy. Despite an adequate duration of rTMS treatment, some patients with post-stroke depression (PSD) do not achieve full symptom response or remission. MethodsThis was a prospective randomized controlled trial. Participants receiving rTMS were randomly assigned to the ventromedial prefrontal cortex (VMPFC), left dorsolateral prefrontal cortex (DLPFC), or contralateral motor area (M1) groups in a ratio of 1:1:1. Enrollment assessments and data collection were performed in weeks 0, 2, 4, and 8. The impact of depressive symptom dimensions on treatment outcomes were tested using a linear mixed-effects model fitted with maximum likelihood. Univariate analysis of variance (ANOVA) and back-testing were used to analyze the differences between the groups. ResultsIn total, 276 patients were included in the analysis. Comparisons across groups showed that 17-item Hamilton Rating Scale for Depression (HAMD-17) scores of the DLPFC group significantly differed from those of the VMPFC and M1 groups at 2, 4, and 8 weeks after treatment (p < 0.05). A higher observed mood score (β = −0.44, 95% confidence interval [CI]: −0.85–0.04, p = 0.030) could predict a greater improvement in depressive symptoms in the DLPFC group. Higher neurovegetative scores (β = 0.60, 95% CI: 0.25–0.96, p = 0.001) could predict less improvement of depressive symptoms in the DLPFC group. ConclusionStimulation of the left DLPFC by high-frequency rTMS (HF-rTMS) could significantly improve depressive symptoms in the subacute period of subcortical ischemic stroke, and the dimension of depressive symptoms at admission might predict the treatment effect.

A randomised sham-controlled study evaluating rTMS analgesic efficacy for postherpetic neuralgia.

Postherpetic neuralgia (PHN) is a refractory neuropathic pain condition in which new treatment options are being developed. Repetitive transcranial magnetic stimulation (rTMS) may have the potential to reduce pain sensations in patients with postherpetic neuralgia. This study investigated the efficacy on postherpetic neuralgia by stimulating two potential targets, the motor cortex (M1) and the dorsolateral prefrontal cortex (DLPFC). This is a double-blind, randomised, sham-controlled study. Potential participants were recruited from Hangzhou First People's Hospital. Patients were randomly assigned to either the M1, DLPFC or Sham group. Patients received ten daily sessions of 10-Hz rTMS in 2 consecutive weeks. The primary outcome measure was visual analogue scale (VAS) assessed at baseline, first week of treatment (week 1), post-treatment (week 2), 1-week (week 4), 1-month (week 6) and 3-month (week 14) follow-up. Of sixty patients enrolled, 51 received treatment and completed all outcome assessments. M1 stimulation resulted in a larger analgesia during and after treatment compared to the Sham (week 2 - week 14, p < 0.005), as well as to the DLPFC stimulation (week 1 - week 14, p < 0.05). In addition to pain, sleep disturbance was significantly improved and relieved by targeting either the M1 or the DLPFC (M1: week 4 - week 14, p < 0.01; DLPFC: week 4 - week 14, p < 0.01). Moreover, pain sensations following M1 stimulation uniquely predicted improvement in sleep quality. M1 rTMS is superior to DLPFC stimulation in treating PHN with excellent pain response and long-term analgesia. Meanwhile, M1 and DLPFC stimulation were equally effective in improving sleep quality in PHN. https://www.chictr.org.cn/, identifier ChiCTR2100051963.

Efficacy of adjunctive intensive transcranial direct current stimulation of different cortices in treatment-resistant depression: a study protocol for a randomized double-blinded sham-controlled trial

BackgroundTreatment-resistant depression (TRD) carries a high economic burden worldwide. Transcranial direct current stimulation (tDCS) is advantageous for improving cognition and can be safely used in the treatment of depression. The effectiveness of tDCS of the left and right orbitofrontal cortex (OFC) as adjuvant treatment in patients with TRD has rarely been explored. Therefore, the objective of this trial is to evaluate the effectiveness there of when administering left dorsolateral prefrontal cortex (DLPFC) positive stimulation or OFC negative stimulation in patients with TRD.MethodsNinety eligible participants will be recruited to receive intervention at Shanghai Mental Health Center. Treatment will be randomly assigned in a double-blind fashion. Participants will receive either DLPFC (n = 30), OFC (n = 30), or sham (n = 30) tDCS, while continuing their usual pharmacotherapy at a stable dosage for at least 2 weeks before enrollment and throughout the stimulation period. All participants will receive 20 weekday stimulation sessions of 60 minutes duration each. Participants in the active group will be stimulated at 2 mA throughout the session, whereas the sham group will receive only a brief period of stimulation to mimic the sensation. After 20 stimulation sessions, no further treatment will be administered. Measurements will be conducted at regular points throughout and at 8 weeks after trial completion. The primary outcome is the change in the 17-item Hamilton Depression Rating Scale (HAMD-17) score after 20 sessions. Secondary outcomes were defined as changes in other measurement scales, cognitive function, resting-state functional magnetic resonance imaging (rs-fMRI), and serum biomarkers.DiscussionWe hypothesize that, in contrast to the sham group, both the active DLPFC and OFC tDCS groups will show superiority in HAMD-17 score reduction after 5, 10, and 20 sessions. Moreover, associations of the improvement of depressive symptoms with variations in rs-fMRI and TRD-related biomarkers will be evaluated. Our study may suggest that adjunctive intensive tDCS with left DLPFC positive stimulation or right OFC negative stimulation may be effective as a novel method to relieve depressive symptoms in patients with TRD. The variation of rs-fMRI, biomarkers could be used as a potential prediction model of treatment efficacy in TRD.Trial registrationThe trial protocol is registered with www.chictr.org.cn under protocol registration number ChiCTR2200058030. Date of registration: March 27, 2022. Recruitment started in September 2022 and is ongoing.

The roles of the LpSTS and DLPFC in self‐prioritization: A transcranial magnetic stimulation study

The Self‐Attention Network (SAN) has been proposed to describe the underlying neural mechanism of the self‐prioritization effect, yet the roles of the key nodes in the SAN—the left posterior superior temporal sulcus (LpSTS) and the dorsolateral prefrontal cortex (DLPFC)—still need to be clarified. One hundred and nine participants were randomly assigned into the LpSTS group, the DLPFC group, or the sham group. We used the transcranial magnetic stimulation (TMS) technique to selectively disrupt the functions of the corresponding targeted region, and observed its impacts on self‐prioritization effect based on the difference between the performance of the self‐matching task before and after the targeted stimulation. We analyzed both model‐free performance measures and HDDM‐based performance measures for the self‐matching task. The results showed that the inhibition of LpSTS could lead to reduced performance in processing self‐related stimuli, which establishes a causal role for the LpSTS in self‐related processing and provide direct evidence to support the SAN framework. However, the results of the DLPFC group from HDDM analysis were distinct from the results based on response efficiency. Our investigation further the understanding of the differentiated roles of key nodes in the SAN in supporting the self‐salience in information processing.

Repetitive transcranial magnetic stimulation for neuropathic pain: a randomized multicentre sham-controlled trial.

Repetitive transcranial magnetic stimulation (rTMS) has been proposed to treat neuropathic pain but the quality of evidence remains low. We aimed to assess the efficacy and safety of neuronavigated rTMS to the primary motor cortex (M1) or dorsolateral prefrontal cortex (DLPFC) in neuropathic pain over 25 weeks. We carried out a randomized double-blind, placebo-controlled trial at four outpatient clinics in France. Patients aged 18-75 years with peripheral neuropathic pain were randomly assigned at a 1:1 ratio to M1 or DLPFC-rTMS and rerandomized at a 2:1 ratio to active or sham-rTMS (10 Hz, 3000 pulses/session, 15 sessions over 22 weeks). Patients and investigators were blind to treatment allocation. The primary end point was the comparison between active M1-rTMS, active DLPCF-rTMS and sham-rTMS for the change over the course of 25 weeks (Group × Time interaction) in average pain intensity (from 0 no pain to 10 maximal pain) on the Brief Pain Inventory, using a mixed model repeated measures analysis in patients who received at least one rTMS session (modified intention-to-treat population). Secondary outcomes included other measures of pain intensity and relief, sensory and affective dimensions of pain, quality of pain, self-reported pain intensity and fatigue (patients diary), Patient and Clinician Global Impression of Change (PGIC, CGIC), quality of life, sleep, mood and catastrophizing. This study is registered with ClinicalTrials.gov NCT02010281. A total of 152 patients were randomized and 149 received treatment (49 for M1; 52 for DLPFC; 48 for sham). M1-rTMS reduced pain intensity versus sham-rTMS (estimate for Group × Session interaction: -0.048 ± 0.02; 95% CI: -0.09 to -0.01; P = 0.01). DLPFC-rTMS was not better than sham (estimate: -0.003 ± 0.01; 95% CI: -0.04 to 0.03, P = 0.9). M1-rRMS, but not DLPFC-rTMS, was also superior to sham-rTMS on pain relief, sensory dimension of pain, self-reported pain intensity and fatigue, PGIC and CGIC. There were no effects on quality of pain, mood, sleep and quality of life as all groups improved similarly over time. Headache was the most common side effect and occurred in 17 (34.7%), 23 (44.2%) and 13 (27.1%) patients from M1, DLPFC and sham groups, respectively (P = 0.2). Our results support the clinical relevance of M1-rTMS, but not of DLPFC-rTMS, for peripheral neuropathic pain with an excellent safety profile.

A Causal Role for the Right Dorsolateral Prefrontal Cortex in Avoidance of Risky Choices and Making Advantageous Selections

In everyday life, risky decision-making relies on multiple cognitive processes including sensitivity to reinforcers, exploration, learning, and forgetting. Neuroimaging evidence suggests that the dorsolateral prefrontal cortex (DLPFC) is involved in exploration and risky decision-making, but the nature of its computations and its causal role remain uncertain. We provide evidence for the role of the DLPFC in value-independent, directed exploration on the Iowa Gambling Task (IGT) and we describe a new computational model to account for the competition of directed exploration and exploitation in guiding decisions. Forty-two healthy human participants were included in a right DLPFC, left DLPFC or sham stimulation groups using continuous theta-burst stimulation (cTBS). Immediately after cTBS, the IGT was completed. Computational modelling was used to account for exploration and exploitation with different combinations with value-based and sensitivity to reinforcers for each group. Applying cTBS to the left and right DLPFC selectively decreased directed exploration on the IGT compared to sham stimulation. Model-based analyses further indicated that the right (but not the left) DLPFC stimulation increased sensitivity to reinforcers, leading to avoidance of risky choices and promoting advantageous choices during the task. Although these findings are based on small sample sizes per group, they nevertheless elucidate the causal role of the right DLPFC in governing the exploration–exploitation tradeoff during decision-making in uncertain and ambiguous contexts.

Effect of Transcranial Direct Current Stimulation on Dorsolateral Prefrontal Cortex to Reduce the Symptoms of the Obsessive-Compulsive Disorder.

Introduction:Obsessive-Compulsive Disorder (OCD) is one of the most common debilitating mental disorders with a prevalence rate of 2% to 3% in the general population. Previous studies have indicated abnormalities in the dorsolateral prefrontal cortex (DLPFC) of OCD patients; thus, we decided to use transcranial Direct Current Stimulation (tDCS) to decline these patients’ symptoms.Methods:A total of 24 patients with OCD participated in this study with the hope of improvement after the application of tDCS. The subjects were randomly assigned to three groups of Sham, Right DLPFC, and Left DLPFC. tDCS was applied for five consecutive days and in each session, patients were subjected to 2 mA current flow for two 15 minutes followed by a 10-minute rest in between (every session lasted for 40 minutes).Results:Subsequently, the changes in obsessive-compulsive level and cognitive functions were evaluated via Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) and Depression, Anxiety, and Stress Scale 21 (DASS-21) by comparing the results before (pre-test) and after (post-test) tDCS treatment.Conclusion:Ultimately, the scores of the Yale-Brown scale in the Left DLPFC group showed significant changes after treatment with tDCS (mean difference compared to the sham group: −6.18 and P≤0.05). Hereupon, this study demonstrated that transcranial direct current stimulation may cause improvements in symptoms of OCD.

Dual-site rTMS is More Effective than Single-site rTMS in Tinnitus Patients: A Blinded Randomized Controlled Trial.

Repetitive transcranial magnetic stimulation (rTMS) has been proposed as an alternative option for treating tinnitus. rTMS is a noninvasive method in which repetitive magnetic stimulation is applied to the cortex; it is considered a therapeutic strategy that modulates the loudness of tinnitus. In this study, we performed a double-blind randomized clinical trial to compare the outcome of tinnitus treatment among (1) dual-site (auditory + prefrontal) rTMS stimulation, (2) auditory cortex only rTMS stimulation (AC), and (3) sham stimulation. The left primary auditory cortex and left dorsolateral prefrontal cortex (DLPFC) were targeted independently of handedness or tinnitus laterality. Dual-site and auditory only groups were treated with a total of 12,000 pulses, 2000 pulses over the AC and 1000 pulses over the DLPFC (group 1), 3000 pulses over the AC only (group 2), and daily for 4 consecutive days. Dual-site group exhibited a significantly better ΔTinnitus Handicap Inventory (ΔTHI) score at 4, 8 weeks and 12 weeks after rTMS treatments compared with pre-treatment. However, there was no effect in the auditory only group. Also, there was no effect in sham group when THI scores were compared with that of the pre-treatment. These results are in line with the former studies that reported a better treatment effect by multiple site rTMS.

Efficacy and clinical predictors of response to rTMS treatment in pharmacoresistant obsessive-compulsive disorder (OCD): a retrospective study

BackgroundApplication of repetitive transcranial magnetic stimulation (rTMS) for treating obsessive-compulsive disorder (OCD) has been promising and approved by the Food and Drug Administration in 2018, but effects differ between patients. Knowledge about clinical predictors of rTMS response may help to increase clinical efficacy but is not available so far.MethodsIn a retrospective study, we investigated the efficacy of rTMS over the dorsolateral prefrontal cortex (DLPFC) or supplementary motor area (SMA) in 65 pharmaco-resistant OCD outpatients recruited for rTMS treatment from July 2015 to May 2017. Patients received either SMA rTMS (n = 38) or bilateral DLPFC rTMS (n = 27) in case of reporting higher affective and depressive symptoms in addition to the primary OCD symptoms. OCD symptoms and depression/anxiety states were measured at baseline (before the 1st session) and after the 20th session of rTMS. Additionally, we performed a binary logistic regression analysis on the demographic and clinical variables based on the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) 3-factor and 2-factor models and individual items to investigate potential predictors of rTMS response.ResultsPatients’ scores in Y-BOCS and Beck anxiety/depression inventories were significantly decreased following rTMS treatment. 46.2% of all patients responded to rTMS, based on the criterion of at least a 30% reduction in Y-BOCS scores. There was no significant difference between response rates of patients in DLPFC and SMA groups. No significant demographic predictors of rTMS efficacy were identified. The factors “obsession severity”, “resistance” and “disturbance” and the “interference due to obsessions” and “resistance against compulsions” items of the Y-BOCS significantly predicted response to rTMS.ConclusionsIn patients with less intrusive/interfering thoughts, and low scores in the “obsession severity”, “disturbance”, and “resistance” factors, rTMS might have superior effects. Identifying clinical and non-clinical predictors of response is relevant to personalize and adapt rTMS protocols in pharmaco-resistant OCD patients. Interpretation of rTMS efficacy should be done with caution due to the lack of a sham intervention condition.

Effects of high-frequency repetitive transcranial magnetic stimulation on reach-to-grasp performance in individuals with Parkinson's disease: a preliminary study.

Individuals with Parkinson's disease (PD) have deficits in reach-to-grasp (RTG) execution and visuospatial processing which may be a result of dopamine deficiency in two brain regions: primary motor cortex (M1) and dorsolateral prefrontal cortex (DLPFC). We hypothesized that improvement following M1 stimulation would be the result of a direct impact on motor execution; whereas, DLPFC stimulation would improve the role of DLPFC in visuospatial processing. The aim of pilot study was to investigate the effects of HF-rTMS on RTG performance by stimulating either M1 or DLPFC. Thirty individuals with PD participated (H&Y stages I-III). All of them were more affected on the right side. Participants were allocated into three groups. The DLPFC group received HF-rTMS over left DLPFC; while, the M1 group received HF-rTMS over left M1 of extensor digitorum communis representational area. The control group received HF-rTMS over the vertex. Before and immediately post HF-rTMS, right-hand RTG performance was measured under no barrier and barrier conditions. Additionally, TMS measures including motor-evoked-potential (MEP) amplitude and cortical silent period (CSP) were determined to verify the effects of HF-rTMS. For the results, there were no significant differences among the three groups. However, only the M1 group showed a significant decrease in movement time immediately after HF-rTMS for a barrier condition. Moreover, the M1 group showed a near-significant increase in hand opening and transport velocity. As for the DLPFC group, there was a near-significant increase in temporal transport-grasp coordination and a significant increase in velocity. Increased MEP amplitudes and a significantly longer CSP in the M1 and DLPFC groups confirmed the effects of HF-rTMS. Regarding non-significant results among the three groups, it is still inconclusive whether there were different effects of the rTMS on the two stimulation areas. This is a preliminary study demonstrating that HF-rTMS to M1 may improve RTG execution; whereas, HF-rTMS to DLPFC may improve visuospatial processing demands of RTG.

Noninvasive brain stimulation over M1 and DLPFC cortex enhances the learning of bimanual isometric force control

Motor learning plays an important role in upper-limb function and the recovery of lost functionality. This study aimed to investigate the relative impact of transcranial direct current stimulation (tDCS) on learning in relation to the left primary motor cortex (M1) and left dorsolateral prefrontal cortex (DLPFC) during bimanual isometric force-control tasks performed with both hands under different task constraints. In a single-blind cross-over design, 20 right-handed participants were randomly assigned to either the M1 group (n = 10; mean age, 22.90 ± 1.66 years, mean ± standard deviation) or the DLPFC group (n = 10; mean age, 23.20 ± 1.54 years). Each participant received 30 min of tDCS (anodal or sham, applied randomly in two experiments) while performing the bimanual force control tasks. Anodal tDCS of the M1 improved the accuracy of maintenance and rhythmic alteration of force tasks, while anodal tDCS of the DLPFC improved only the maintenance of the force control tasks compared with sham tDCS. Hence, tDCS over the left M1 and DLPFC has a beneficial effect on the learning of bimanual force control.

Comparing the Efficacy of Anodal, Cathodal, and Sham Transcranial Direct Current Stimulation on Brain-Derived Neurotrophic Factor and Psychological Symptoms in Opioid-Addicted Patients.

Introduction:Today, addiction to opioids is a serious problem all over the world. Unfortunately, the consumption of these drugs and the number of addicted people have drastically increased. This research aimed at comparing the efficacy of anodal, cathodal, and sham transcranial Direct Current Stimulation (tDCS) on the Brain-Derived Neurotrophic Factor (BDNF) and psychological symptoms in opioid-addicted patients.Methods:Thirty opioid-addicted patients were selected based on the Diagnostic and Statistical Manual of Mental Disorders, the Fifth Edition, through the convenience sampling method. They were then randomly assigned to 3 groups (10 in each group). The subjects were evaluated before and after tDCS by their serum level of BDNF, desires for drug questionnaire, and depression anxiety stress scale. The data were analyzed by the Kolmogorov-Smirnov test, one-way analysis of variance, as well as the Bonferroni test.Results:Stimulating the Dorsolateral Prefrontal Cortex (DLPFC) led to a significant change in increasing the level of BDNF (P=0.031) and reducing the degree of depression (P=0.018), anxiety (P=0.001), stress (P=0.012), and decreased the level of craving (P=0.001) in opioid-addicted patients. There was no significant difference between active stimulation groups (anodal left/cathodal right and anodal right/cathodal left). The stimulation of the right DLPFC (group B) significantly increased BDNF in comparison with the sham group (sham tDCS) and decreased anxiety and craving. Nonetheless, no change was observed in depression and stress. The stimulation of the left DLPFC (group A) significantly reduced depression, anxiety, stress, and craving compared with the sham group, while there was no change in BDNF.Conclusion:In addition to the conventional treatments of opioid-addicted patients, tDCS is an effective complementary treatment.

Researching Hemispheric Specialization in the Control of Final Position Accuracy Using the Transcranial Direct Current Stimulation

Transcranial Direct Current Simulation (tDCS) can improve or disrupt brain functions and can therefore be used to investigate hemispheric specialization. Accordingly, this study was designed to research hemispheric specialization in the control of final position accuracy by comparing the effects of tDCS on dorsolateral prefrontal cortex (DLPFC) in the right and left hemispheres. Forty-three right-handed male university students (aged 21.34±1.61) volunteered to participate in this study. They were divided into the right DLPFC, left DLPFC, sham, and practice groups, including 12, 11, 9, and 11 participants, respectively. After learning motor skills in two days, the participants practiced final position accuracy in one day. They were asked to move the cursor toward the centers of targets appearing randomly at the top, middle, and bottom on the right side of a monitor as accurately and quickly as they could. At the time of practice, the participants received anodic stimulation in one hemisphere and cathodic stimulation in the other. The results indicated that the left anodic/right cathodic group (left DLPFC) showed the worst performance, which may be caused by the inhibitory effects of cathodic stimulations in the right DLPFC. Therefore, it is predicted that the right hemisphere may have greater specialization in final position accuracy of movement.

Stimulation of Dorsolateral Prefrontal Cortex Enhances Adaptive Cognitive Control: A High-Definition Transcranial Direct Current Stimulation Study.

Conflict adaptation is a hallmark effect of adaptive cognitive control. While animal studies have suggested causal involvement of the DLPFC in this phenomenon, such evidence is currently lacking in humans. The present study used high-definition transcranial direct current stimulation (HD-tDCS) to demonstrate that the DLPFC is causally involved in conflict adaptation in humans. Our study confirms a central claim of conflict monitoring theory, which up to now has predominantly relied on correlational studies. Our results further indicate an equal involvement of the left and right DLPFC in adaptive control, whereas stimulation of a control region-the primary motor cortex-had no effect on adaptive control. The study thus confirms the potential of HD-tDCS to modulate cognition in a regionally specific manner.

Role of the dorsolateral prefrontal cortex in context-dependent motor performance.

Context-dependent motor performance is a phenomenon in which people perform better in the environmental context where they originally practised a task. Some animal and computer simulation studies have suggested that context-dependent performance may be associated with neural activation of the dorsolateral prefrontal cortex (DLPFC). This study aimed to determine the role of the DLPFC in context-dependent motor performance by perturbing the neural processing of the DLPFC with repetitive transcranial magnetic stimulation (rTMS) in healthy adults. Thirty healthy adults were recruited into the Control, rTMS DLPFC and rTMS Vertex groups. The participants practised three finger sequences associated with a specific incidental context (a coloured circle and a location on the computer screen). One day following practice, the rTMS groups received 1 Hz rTMS prior to the testing conditions in which the sequence-context associations remained the same as practice (SAME) or changed (SWITCH). All three groups improved significantly over practice on day 1. The second day testing results showed that the DLPFC group had a significantly lower decrease in motor performance under the SWITCH condition than the Control and Vertex groups. This finding suggests a specific role of the DLPFC in context-dependent motor performance.

Multiple bout rTMS on spatial working memory: A comparison study of two cortical areas

It has been established that acute (within-session) repetitive transcranial magnetic stimulation (rTMS) improves spatial working memory (SWM). However, questions remain regarding the safety and effectiveness of multiple bouts of rTMS and the optimal cortical area to stimulate. This preliminary study investigated, in healthy participants, multiple bouts of rTMS over the dorsolateral pre-frontal cortex (DLPFC), or posterior parietal cortex (PPC) on SWM. Twenty participants (10m, 10f), all naïve to rTMS, where randomized into a DLPFC or PPC group, receiving six sessions of rTMS (5Hz at 80% of motor threshold) every second day over two weeks. Prior to and post rTMS bouts, all participants completed testing for SWM measuring individuals’ accuracy, strategy, and speed. Following repeated bouts of rTMS, significant improvements were observed with no contraindications in stimulating PPC but not DLPFC. This preliminary study has demonstrated that repeated rTMS bouts improve SWM safety providing potential for clinical application.