Group and Individual Level Variations between Symmetric and Asymmetric DLPFC Montages for tDCS over Large Scale Brain Network Nodes

Soleimani, Ghazaleh; Saviz, Mehrdad; Bikson, Marom; Towhidkhah, Farzad; Kuplicki, Rayus; Paulus, Martin P.; Ekhtiari, Hamed

doi:10.1101/2020.06.10.141853

Cited by 9 publications

(17 citation statements)

References 72 publications

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“…up to 2 ms) alternating stimulation of left and right DLPFCs with the SD montage may have induced such inter-hemispheric inhibition in the present study, which could have lead to an absence of behavioral difference with the Sham group. This superiority of unilateral over bilateral montage has been previously observed in a tDCS methodological article 65 . The authors measured a higher electrical dose within the targeted DLPFC and also within the connected network nodes (i.e.…”

Section: Discussionsupporting

confidence: 69%

Performance after training in a complex cognitive task is enhanced by high-definition transcranial random noise stimulation

Chenot

Hamery

Lepron

et al. 2022

Sci Rep

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Interest for neuromodulation, and transcranial random noise stimulation (tRNS) in particular, is growing. It concerns patients rehabilitation, but also healthy people who want or need to improve their cognitive and learning abilities. However, there is no consensus yet regarding the efficacy of tRNS on learning and performing a complex task. In particular, the most effective electrode montage is yet to be determined. Here, we examined the effect of two different tRNS montages on learning rate, short- and long-term performance in a video game (Space Fortress) that engages multiple cognitive abilities. Sixty-one participants were randomly assigned to one of three groups (sham vs. simple-definition tRNS vs. high-definition tRNS) in a double-blind protocol. Their performance on the Space Fortress task was monitored during a 15-day experiment with baseline (day 1), stimulation (day 2 to 4), short- (day 5) and long-term (day 15) evaluations. Our results show that the high-definition tRNS group improved more on the long term than simple-definition tRNS group, tended to learn faster and had better performance retention compared to both simple-definition tRNS and sham groups. This study is the first to report that high-definition tRNS is more effective than conventional simple-definition tRNS to enhance performance in a complex task.

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Section: Discussionsupporting

confidence: 69%

Performance after training in a complex cognitive task is enhanced by high-definition transcranial random noise stimulation

Chenot

Hamery

Lepron

et al. 2022

Sci Rep

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“…No significant results were found within the other networks. The main resons for finding significant associations only in ECN and DMN (and not other brain networks) might be related to strong EFs in these two networks [32].…”

Section: Discussionmentioning

confidence: 94%

Dose-Response in Modulating Brain Function with Transcranial Direct Current Stimulation: From Local to Network Levels

Soleimani

Kuplicki

Paulus

et al. 2022

Preprint

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Background: Non-invasive brain stimulation methods for modulating brain activity via transcranial technologies like transcranial direct current stimulation (tDCS) are increasingly prevalent to investigate the relationship between modulated brain regions and stimulation outcomes. However, the inter-individual variability of tDCS has made it challenging to detect intervention effects at the group level. Collecting multiple modalities of magnetic resonance imaging data (i.e., structural and functional MRI) helps to investigate how dose-response ultimately shapes brain function in response to tDCS. Method: We collected data in a randomized, triple-blind, sham-controlled trial with two parallel arms. Sixty participants with MUD were randomly assigned to sham or active tDCS (n=30 per group, 2 mA, 20 minutes, anode/cathode over F4/Fp1). Structural and functional MRI (including high-resolution T1 and T2-weighted MRI, resting-state fMRI, and methamphetamine cue-reactivity task with meth versus neutral cues) were collected immediately before and after tDCS. T1 and T2-weighted MRI data were used to generate head models for each individual to simulate electric fields. Associations between electric fields (dose) and changes in brain function (response) were investigated at four different levels: (1) voxel level, (2) regional level (atlas-based parcellation), (3) cluster level (active clusters in the contrast of interest), and (4) network level (both task-based and resting-state networks). Result: At the (1) voxel-level, (2) regional level, and (3) cluster level, our results showed no significant correlation between changes in the functional activity and electric fields. However, (4) at the network level, a significant negative correlation was found between the electric field and ReHo in the default mode network (r=-0.46 (medium effect size), p corrected=0.018). For the network-level analysis of task-based fMRI data, frontoparietal connectivity showed a positive significant correlation with the electric field in the frontal stimulation site (r=0.41 (medium effect size), p corrected=0.03). Conclusion: The proposed pipeline provides a methodological framework to analyze tDCS effects in terms of dose-response relationships at four different levels to directly link the electric field (dose) variability to the variability of the neural response to tDCS. The results suggest that network-based analysis might be a better approach to provide novel insights into the dependency of the neuromodulatory effects of tDCS on the regional current dose in each individual. Dose-response integration can be informative for dose optimization/customization or predictive/treatment-response biomarker extraction in future brain stimulation studies.

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“…One of the factors limiting the therapeutic potential of tDCS is the high inter-subject variability of behavioural effects. It has been suggested that this might, at least in part, be due to the use of a standard extracranial current intensity across participants, which will inevitably lead to variability in the E-field applied in the cortex (Abellaneda-Pérez et al, 2020; Kim et al, 2014; Laakso et al, 2015; Mezger et al,2021; Soleimani et al, 2021). Supporting this theory, tDCS-induced behavioural outcomes such as improvements in working memory have been related to the applied E-field (Albizu et al, 2020).…”

Section: Discussionmentioning

confidence: 99%

tDCS induced GABA change is associated with the simulated electric field in M1, an effect mediated by grey matter volume in the MRS voxel

Puonti

Clarke

Nettekoven

et al. 2022

Preprint

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Background and ObjectiveTranscranial direct current stimulation (tDCS) has wide ranging applications in neuro-behavioural and physiological research, and in neurological rehabilitation. However, it is currently limited by substantial inter-subject variability in responses, which may be explained, at least in part, by anatomical differences that lead to variability in the electric field (E-field) induced in the cortex. Here, we tested whether the variability in the E-field in the stimulated cortex during tDCS, estimated using computational simulations, explains the variability in tDCS induced changes in GABA, a neurophysiological marker of stimulation effect.MethodsData from five previously conducted MRS studies were combined. The anode was placed over the left primary motor cortex (M1, 3 studies, N = 24) or right temporal cortex (2 studies, N = 32), with the cathode over the contralateral supraorbital ridge. Single voxel spectroscopy was performed in a 2×2×2cm voxel under the anode in all cases. MRS data were acquired before and either during or after 1mA tDCS using either a sLASER sequence (7T) or a MEGA-PRESS sequence (3T). sLASER MRS data were analysed using LCModel, and MEGA-PRESS using FID-A and Gannet. E-fields were simulated in a finite element model of the head, based on individual MPRAGE images, using SimNIBS. Separate linear mixed effects models were run for each E-field variable (mean and 95th percentile; magnitude, and components normal and tangential to grey matter surface, within the MRS voxel). The model included effects of time (pre or post tDCS), E-field, grey matter volume in the MRS voxel, and a 3-way interaction between time, E-field and grey matter volume. Additionally, we ran a permutation analysis using PALM to determine whether E-field anywhere in the brain, not just in the MRS voxel, correlated with GABA change.ResultsIn M1, higher mean E-field magnitude was associated with greater tDCS-induced decreases in GABA (t(24) = 3.24, p = 0.003). Further, the association between mean E-field magnitude and GABA change was moderated by the grey matter volume in the MRS voxel (t(24) = −3.55, p =0.002). These relationships were consistent across all E-field variables except the mean of the normal component. No significant relationship was found between tDCS-induced GABA decrease and E-field in the temporal voxel. No significant clusters were found in the whole brain analysis.ConclusionsOur data suggest that the electric field induced by tDCS within the brain is variable, and is significantly related to tDCS-induced decrease in GABA, a key neurophysiological marker of stimulation. These findings strongly support individualised dosing of tDCS, at least in M1. Further studies examining E-fields in relation to other outcome measures, including behaviour, will help determine the optimal E-fields required for any desired effects.HighlightsWe study the link between individually simulated electric field dose and tDCS-induced change in GABA in the cortex.The electric field strength in the brain correlates with a decrease in GABA in the motor cortex.The correlation between the electric field and GABA change is modulated by the amount of grey matter in the MRS voxel.We find no association between the electric field and GABA in the temporal cortex.

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Group and Individual Level Variations between Symmetric and Asymmetric DLPFC Montages for tDCS over Large Scale Brain Network Nodes

Cited by 9 publications

References 72 publications

Performance after training in a complex cognitive task is enhanced by high-definition transcranial random noise stimulation

Performance after training in a complex cognitive task is enhanced by high-definition transcranial random noise stimulation

Dose-Response in Modulating Brain Function with Transcranial Direct Current Stimulation: From Local to Network Levels

tDCS induced GABA change is associated with the simulated electric field in M1, an effect mediated by grey matter volume in the MRS voxel

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