scholarly journals Focality-Oriented Selection of Current Dose for Transcranial Direct Current Stimulation

2021 ◽  
Vol 11 (9) ◽  
pp. 940
Author(s):  
Rajan Kashyap ◽  
Sagarika Bhattacharjee ◽  
Ramaswamy Arumugam ◽  
Rose Dawn Bharath ◽  
Kaviraja Udupa ◽  
...  
Keyword(s):  
Older Adults ◽  
Direct Current ◽  
Current Density ◽  
Transcranial Direct Current Stimulation ◽  
Age Groups ◽  
Average Current Density ◽  
Peak Region ◽  
Direct Current Stimulation ◽  
Reference Space ◽  
The Brain

Background: In transcranial direct current stimulation (tDCS), the injected current becomes distributed across the brain areas. The objective is to stimulate the target region of interest (ROI) while minimizing the current in non-target ROIs (the ‘focality’ of tDCS). For this purpose, determining the appropriate current dose for an individual is difficult. Aim: To introduce a dose–target determination index (DTDI) to quantify the focality of tDCS and examine the dose–focality relationship in three different populations. Method: Here, we extended our previous toolbox i-SATA to the MNI reference space. After a tDCS montage is simulated for a current dose, the i-SATA(MNI) computes the average (over voxels) current density for every region in the brain. DTDI is the ratio of the average current density at the target ROI to the ROI with a maximum value (the peak region). Ideally, target ROI should be the peak region, so DTDI shall range from 0 to 1. The higher the value, the better the dose. We estimated the variation of DTDI within and across individuals using T1-weighted brain images of 45 males and females distributed equally across three age groups: (a) young adults (20 ≤ x ˂ 40 years), (b) mid adults (40 ≤ x ˂ 60 years), and (c) older adults (60 ≤ x ˂ 80 years). DTDI’s were evaluated for the frontal montage with electrodes at F3 and the right supraorbital for three current doses of 1 mA, 2 mA, and 3 mA, with the target ROI at the left middle frontal gyrus. Result: As the dose is incremented, DTDI may show (a) increase, (b) decrease, and (c) no change across the individuals depending on the relationship (nonlinear or linear) between the injected tDCS current and the distribution of current density in the target ROI. The nonlinearity is predominant in older adults with a decrease in focality. The decline is stronger in males. Higher current dose at older age can enhance the focality of stimulation. Conclusion: DTDI provides information on which tDCS current dose will optimize the focality of stimulation. The recommended DTDI dose should be prioritized based on the age (>40 years) and sex (especially for males) of an individual. The toolbox i-SATA(MNI) is freely available.

scholarly journals Focality Oriented Selection of Current Dose for Transcranial Direct Current Stimulation

2021 ◽  
Author(s):  
Rajan Kashyap ◽  
Sagarika Bhattacharjee ◽  
Ramaswamy Arumugam ◽  
Rose Dawn Bharath ◽  
Kaviraja Udupa ◽  
...  
Keyword(s):  
Direct Current ◽  
Current Density ◽  
Transcranial Direct Current Stimulation ◽  
Age Groups ◽  
Region Of Interest ◽  
Average Current Density ◽  
Peak Region ◽  
Direct Current Stimulation ◽  
Reference Space ◽  
The Brain

Background: In Transcranial Direct Current Stimulation (tDCS) the injected current gets distributed across the brain areas. The motive is to stimulate the target region-of-interest (ROI), while minimizing the current in non-target ROIs. For this purpose, determining the appropriate current-dose for an individual is difficult. Aim: To introduce Dose-Target-Determination-Index (DTDI) to quantify the focality of tDCS and examine the dose-focality relationship in three different populations. Method: Here, we extended our previous toolbox i-SATA to the MNI reference space. After a tDCS montage is simulated for a current-dose, the i-SATA(MNI) computes the average (over voxels) current density for every region in the brain. DTDI is the ratio of average current density at target ROI to the ROI with maximum value (peak region). Ideally target ROI should be the peak region, so DTDI shall range from 0 to 1. Higher the value, the better the dose. We estimated the variation of DTDI within and across individuals using T1-weighted brain images of 45 males and females distributed equally across three age groups- (a) Young adults (20 ≥ x ˂ 40 years), (b) Mid adults (40 ≥ x ˂ 60 years), and (c) Older adults (60 ≥ x ˂ 80 years). DTDI’s were evaluated for the frontal montage with electrodes at F3 and right supra-orbital for three current doses 1mA, 2mA, and 3mA with the target ROI at left middle frontal gyrus. Result: As the dose is incremented, DTDI may show (a) increase, (b) decrease, and (c) no change across the individuals. The focality decreases with age and the decline is stronger in males. Higher current dose at older age can enhance the focality of stimulation. Conclusion: DTDI provides information on which tDCS current dose will optimize the focality of stimulation. DTDI recommended dose should be prioritised based on the age (> 40 years) and sex (especially males) of an individual. The toolbox i-SATA(MNI) is freely available.

scholarly journals Multifocal Transcranial Direct Current Stimulation Modulates Resting-State Functional Connectivity in Older Adults Depending on the Induced Current Density

2021 ◽  
Vol 13 ◽  
Author(s):  
Kilian Abellaneda-Pérez ◽  
Lídia Vaqué-Alcázar ◽  
Ruben Perellón-Alfonso ◽  
Cristina Solé-Padullés ◽  
Núria Bargalló ◽  
...  
Keyword(s):  
Older Adults ◽  
Electric Current ◽  
Direct Current ◽  
Current Density ◽  
Transcranial Direct Current Stimulation ◽  
Resting State ◽  
Electric Current Density ◽  
Direct Current Stimulation ◽  
Induced Changes ◽  
The Brain

Combining non-invasive brain stimulation (NIBS) with resting-state functional magnetic resonance imaging (rs-fMRI) is a promising approach to characterize and potentially optimize the brain networks subtending cognition that changes as a function of age. However, whether multifocal NIBS approaches are able to modulate rs-fMRI brain dynamics in aged populations, and if these NIBS-induced changes are consistent with the simulated electric current distribution on the brain remains largely unknown. In the present investigation, thirty-one cognitively healthy older adults underwent two different multifocal real transcranial direct current stimulation (tDCS) conditions (C1 and C2) and a sham condition in a crossover design during a rs-fMRI acquisition. The real tDCS conditions were designed to electrically induce two distinct complex neural patterns, either targeting generalized frontoparietal cortical overactivity (C1) or a detachment between the frontal areas and the posteromedial cortex (C2). Data revealed that the two tDCS conditions modulated rs-fMRI differently. C1 increased the coactivation of multiple functional couplings as compared to sham, while a smaller number of connections increased in C1 as compared to C2. At the group level, C1-induced changes were topographically consistent with the calculated electric current density distribution. At the individual level, the extent of tDCS-induced rs-fMRI modulation in C1 was related with the magnitude of the simulated electric current density estimates. These results highlight that multifocal tDCS procedures can effectively change rs-fMRI neural functioning in advancing age, being the induced modulation consistent with the spatial distribution of the simulated electric current on the brain. Moreover, our data supports that individually tailoring NIBS-based interventions grounded on subject-specific structural data might be crucial to increase tDCS potential in future studies amongst older adults.

scholarly journals Effects of Transcranial Direct Current Stimulation on Neural Networks in Young and Older Adults

2017 ◽  
Vol 29 (11) ◽  
pp. 1817-1828 ◽  
Author(s):  
Andrew K. Martin ◽  
Marcus Meinzer ◽  
Robert Lindenberg ◽  
Mira M. Sieg ◽  
Laura Nachtigall ◽  
...  
Keyword(s):  
Older Adults ◽  
Direct Current ◽  
Transcranial Direct Current Stimulation ◽  
Age Groups ◽  
Anterior Cingulate ◽  
Semantic Fluency ◽  
Motor Speech ◽  
Word Generation ◽  
Direct Current Stimulation ◽  
Components Analysis

Transcranial direct current stimulation (tDCS) may be a viable tool to improve motor and cognitive function in advanced age. However, although a number of studies have demonstrated improved cognitive performance in older adults, other studies have failed to show restorative effects. The neural effects of beneficial stimulation response in both age groups is lacking. In the current study, tDCS was administered during simultaneous fMRI in 42 healthy young and older participants. Semantic word generation and motor speech baseline tasks were used to investigate behavioral and neural effects of uni- and bihemispheric motor cortex tDCS in a three-way, crossover, sham tDCS controlled design. Independent components analysis assessed differences in task-related activity between the two age groups and tDCS effects at the network level. We also explored whether laterality of language network organization was effected by tDCS. Behaviorally, both active tDCS conditions significantly improved semantic word retrieval performance in young and older adults and were comparable between groups and stimulation conditions. Network-level tDCS effects were identified in the ventral and dorsal anterior cingulate networks in the combined sample during semantic fluency and motor speech tasks. In addition, a shift toward enhanced left laterality was identified in the older adults for both active stimulation conditions. Thus, tDCS results in common network-level modulations and behavioral improvements for both age groups, with an additional effect of increasing left laterality in older adults.

scholarly journals 𝓲-SATA: A MATLAB based toolbox to estimate Current Density generated by Transcranial Direct Current Stimulation in an Individual Brain

2020 ◽  
Author(s):  
Rajan Kashyap ◽  
Sagarika Bhattacharjee ◽  
Ramaswamy Arumugam ◽  
Kenichi Oishi ◽  
John E. Desmond ◽  
...  
Keyword(s):  
Direct Current ◽  
Current Density ◽  
Transcranial Direct Current Stimulation ◽  
Anterior Commissure ◽  
Weak Current ◽  
Posterior Commissure ◽  
Direct Current Stimulation ◽  
Total Current Density ◽  
Magnetic Resonance Imaging Mri ◽  
The Brain

AbstractBackgroundTranscranial Direct Current Stimulation (tDCS) is a technique where a weak current is passed through the electrodes placed on the scalp. The distribution of the electric current induced in the brain due to tDCS is provided by simulation toolbox like Realistic-volumetric-Approach-based-Simulator-for-Transcranial-electric-stimulation (ROAST). However, the procedure to estimate the total current density induced at the target and the intermediary region of the cortex is complex. The Systematic-Approach-for-tDCS-Analysis (SATA) was developed to overcome this problem. However, SATA is limited to standardized headspace only. Here we develop individual-SATA (𝓲-SATA) to extend it to individual head.MethodT1-weighted images of 15 subjects were taken from two Magnetic Resonance Imaging (MRI) scanners of different strengths. Across the subjects, the montages were simulated in ROAST. 𝓲-SATA converts the ROAST output to Talairach space. The x, y and z coordinates of the anterior commissure (AC), posterior commissure (PC), and Mid-Sagittal (MS) points are necessary for the conversion. AC and PC are detected using the acpcdetect toolbox. We developed a method to determine the MS in the image and cross-verified its location manually using BrainSight®.ResultDetermination of points with 𝓲-SATA is fast and accurate. The 𝓲-SATA provided estimates of the current-density induced across an individual’s cortical lobes and gyri as tested on images from two different scanners.ConclusionResearchers can use 𝓲-SATA for customizing tDCS-montages. With 𝓲-SATA it is also easier to compute the inter-individual variation in current-density across the target and intermediary regions of the brain. The software is publicly available.

scholarly journals Transcranial Direct Current Stimulation Combined With Meditation for Older Adults With Knee Osteoarthritis

2020 ◽  
Vol 4 (Supplement_1) ◽  
pp. 205-205
Author(s):  
Hyochol Ahn ◽  
Lindsey Park ◽  
Hongyu Miao
Keyword(s):  
Older Adults ◽  
Direct Current ◽  
Transcranial Direct Current Stimulation ◽  
Clinical Symptoms ◽  
Direct Current Stimulation ◽  
Knee Oa ◽  
Home Based ◽  
Common Causes ◽  
Central Pain Processing ◽  
The Brain

Abstract Osteoarthritis (OA) of the knee is one of the most common causes of pain in older adults. Recent evidence suggests that knee OA pain is characterized by alterations in central pain processing in the brain. Two nonpharmacological pain treatments, transcranial direct current stimulation (tDCS) and mindfulness-based meditation (MBM), have been shown to improve pain-related brain function in older adults with knee OA. Because tDCS promotes neuroplasticity, it may potentiate the effect of MBM that also stimulates adaptive changes in the brain. However, no studies have examined whether tDCS combined with MBM can reduce OA symptoms in older adults with knee OA. Thus, the purpose of this study was to examine the preliminary efficacy of tDCS combined with MBM in older adults with knee OA. Thirty participants with knee OA were randomly assigned to receive 10 daily sessions of home-based 2 mA tDCS combined with active MBM for 20 minutes (n=15) or sham tDCS combined with sham MBM (n=15). We measured OA-related clinical symptoms using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Participants (60% female) had a mean age of 59 years. Active tDCS combined with active MBM significantly reduced scores on the WOAMC (Cohen’s d = 0.83, P = 0.02). Participants tolerated tDCS combined with MBM well without serious adverse effects. Our findings demonstrate promising clinical efficacy of home-based tDCS combined with MBM for older adults with knee OA. Future studies with larger-scale randomized controlled trials with follow-up assessments are needed to validate our findings.

scholarly journals Can Transcranial Direct Current Stimulation Enhance Functionality in Older Adults? A Systematic Review

2021 ◽  
Vol 10 (13) ◽  
pp. 2981
Author(s):  
Andrés Pino-Esteban ◽  
Álvaro Megía-García ◽  
David Martín-Caro Álvarez ◽  
Hector Beltran-Alacreu ◽  
Juan Avendaño-Coy ◽  
...  
Keyword(s):  
Systematic Review ◽  
Older Adults ◽  
Direct Current ◽  
Transcranial Direct Current Stimulation ◽  
Randomized Clinical Trials ◽  
Scientific Evidence ◽  
Healthy Older Adults ◽  
Sham Stimulation ◽  
Direct Current Stimulation ◽  
Potential Benefits

Transcranial direct current stimulation (tDCS) is a non-invasive, easy to administer, well-tolerated, and safe technique capable of affecting brain excitability, both at the cortical and cerebellum levels. However, its effectiveness has not been sufficiently assessed in all population segments or clinical applications. This systematic review aimed at compiling and summarizing the currently available scientific evidence about the effect of tDCS on functionality in older adults over 60 years of age. A search of databases was conducted to find randomized clinical trials that applied tDCS versus sham stimulation in the above-mentioned population. No limits were established in terms of date of publication. A total of 237 trials were found, of which 24 met the inclusion criteria. Finally, nine studies were analyzed, including 260 healthy subjects with average age between 61.0 and 85.8 years. Seven of the nine included studies reported superior improvements in functionality variables following the application of tDCS compared to sham stimulation. Anodal tDCS applied over the motor cortex may be an effective technique for improving balance and posture control in healthy older adults. However, further high-quality randomized controlled trials are required to determine the most effective protocols and to clarify potential benefits for older adults.

scholarly journals Effects of transcranial direct current stimulation combined with listening to preferred music on memory in older adults

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ricky Chow ◽  
Alix Noly-Gandon ◽  
Aline Moussard ◽  
Jennifer D. Ryan ◽  
Claude Alain
Keyword(s):  
Older Adults ◽  
Working Memory ◽  
Recognition Memory ◽  
Direct Current ◽  
Transcranial Direct Current Stimulation ◽  
Digit Span ◽  
Recognition Task ◽  
Music Listening ◽  
Subsequent Performance ◽  
Direct Current Stimulation

AbstractListening to autobiographically-salient music (i.e., music evoking personal memories from the past), and transcranial direct current stimulation (tDCS) have each been suggested to temporarily improve older adults’ subsequent performance on memory tasks. Limited research has investigated the effects of combining both tDCS and music listening together on cognition. The present study examined whether anodal tDCS stimulation over the left dorsolateral prefrontal cortex (2 mA, 20 min) with concurrent listening to autobiographically-salient music amplified subsequent changes in working memory and recognition memory in older adults than either tDCS or music listening alone. In a randomized sham-controlled crossover study, 14 healthy older adults (64–81 years) participated in three neurostimulation conditions: tDCS with music listening (tDCS + Music), tDCS in silence (tDCS-only), or sham-tDCS with music listening (Sham + Music), each separated by at least a week. Working memory was assessed pre- and post-stimulation using a digit span task, and recognition memory was assessed post-stimulation using an auditory word recognition task (WRT) during which electroencephalography (EEG) was recorded. Performance on the backwards digit span showed improvement in tDCS + Music, but not in tDCS-only or Sham + Music conditions. Although no differences in behavioural performance were observed in the auditory WRT, changes in neural correlates underlying recognition memory were observed following tDCS + Music compared to Sham + Music. Findings suggest listening to autobiographically-salient music may amplify the effects of tDCS for working memory, and highlight the potential utility of neurostimulation combined with personalized music to improve cognitive performance in the aging population.

Converging Evidence That Neural Plasticity Underlies Transcranial Direct-Current Stimulation

2021 ◽  
Vol 33 (1) ◽  
pp. 146-157
Author(s):  
Chong Zhao ◽  
Geoffrey F. Woodman
Keyword(s):  
Visual Search ◽  
Direct Current ◽  
Neural Plasticity ◽  
Transcranial Direct Current Stimulation ◽  
Time Course ◽  
Memory Task ◽  
Long Term Memory ◽  
Visual Stream ◽  
Direct Current Stimulation ◽  
The Brain

It is not definitely known how direct-current stimulation causes its long-lasting effects. Here, we tested the hypothesis that the long time course of transcranial direct-current stimulation (tDCS) is because of the electrical field increasing the plasticity of the brain tissue. If this is the case, then we should see tDCS effects when humans need to encode information into long-term memory, but not at other times. We tested this hypothesis by delivering tDCS to the ventral visual stream of human participants during different tasks (i.e., recognition memory vs. visual search) and at different times during a memory task. We found that tDCS improved memory encoding, and the neural correlates thereof, but not retrieval. We also found that tDCS did not change the efficiency of information processing during visual search for a certain target object, a task that does not require the formation of new connections in the brain but instead relies on attention and object recognition mechanisms. Thus, our findings support the hypothesis that direct-current stimulation modulates brain activity by changing the underlying plasticity of the tissue.

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