Electric Field Strength From Prefrontal Transcranial Direct Current Stimulation Determines Degree of Working Memory Response: A Potential Application of Reverse-Calculation Modeling?

Caulfield, Kevin A.; Indahlastari, Aprinda; Nissim, Nicole R.; Lopez, James W; Fleischmann, Holly; Woods, Adam J.; George, Mark S.

doi:10.1111/ner.13342

Cited by 36 publications

(42 citation statements)

References 111 publications

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“…Recent tDCS modeling studies have shown that interindividual variability in anatomy has an important role in altering delivered tDCS current in the brain. 88,[96][97][98][99][100] In older adults, age-related effects such as brain atrophy and white matter hyperintensities (WMH) were found as important factors that affect modeled field distribution following tDCS. 77,101 Brain atrophy is commonly described as a shrinkage of cortical structures that occurs with healthy aging.…”

Section: Implications For Tdcs Application In Older Adultsmentioning

confidence: 99%

A Systematic Review and Meta-Analysis of Transcranial Direct Current Stimulation to Remediate Age-Related Cognitive Decline in Healthy Older Adults

Indahlastari¹,

Hardcastle²,

Albizu³

et al. 2021

NDT

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Background: Transcranial direct current stimulation (tDCS) has been proposed as a possible method for remediating age-associated cognitive decline in the older adult population. While tDCS has shown potential for improving cognitive functions in healthy older adults, stimulation outcomes on various cognitive domains have been mixed. Methods: A systematic search was performed in four databases: PubMed, EMBASE, Web of Science, and PsychInfo. Search results were then screened for eligibility based on inclusion/exclusion criteria to only include studies where tDCS was applied to improve cognition in healthy older adults 65 years and above. Eligible studies were reviewed and demographic characteristics, tDCS dose parameters, study procedures, and cognitive outcomes were extracted. Reported effect sizes for active compared to sham group in representative cognitive domain were converted to Hedges' g. Main Results: A total of thirteen studies involving healthy older adults (n=532, mean age=71.2+5.3 years) were included in the meta-analysis. The majority of included studies (94%) targeted the prefrontal cortex with stimulation intensity 1-2 mA using various electrode placements with anodes near the frontal region. Across all studies, we found Hedges' g values ranged from −0.31 to 1.85 as reported group effect sizes of active stimulation compared to sham. Conclusion: While observed outcomes varied, overall findings indicated promising effects of tDCS to remediate cognitive aging and thus deserves further exploration. Future characterization of inter-individual variability in tDCS dose response and applications in larger cohorts are warranted to further validate benefits of tDCS for cognition in healthy older adults.

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Section: Implications For Tdcs Application In Older Adultsmentioning

confidence: 99%

A Systematic Review and Meta-Analysis of Transcranial Direct Current Stimulation to Remediate Age-Related Cognitive Decline in Healthy Older Adults

Indahlastari¹,

Hardcastle²,

Albizu³

et al. 2021

NDT

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“…The current dose calculated through inverse modelling of the tDCS-induced electric field at the target ROI correlates with the motor thresholds generated by transcranial magnetic stimulation [ 15 ]. In a recent tDCS experiment using a frontal montage and a 2 mA (fixed) current dose, individuals with a high current density at the target ROI (left dorsolateral prefrontal cortex) were found to have stronger improvements in working memory compared to those with a low current density [ 21 ]. They also showed that individualizing the current dose by fixing the desired current density at the target region can maximize the benefits of tDCS [ 21 ].…”

Section: Introductionmentioning

confidence: 99%

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

Kashyap

Bhattacharjee

Arumugam

et al. 2021

JPM

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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.

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“…The study extends the i-SATA framework to the MNI atlas space. With i-SATA (MNI), it will be easier to calculate the individualized dose as suggested in previous studies [15,16,20,21]. Here we introduce the DTDI as measure to titrate the individualized current doses and select the optimum dose that has high focality and could appropriately stimulate the target ROI in an individual.…”

Section: Discussionmentioning

confidence: 99%

“…In a recent tDCS experiment using frontal montage and 2mA (fixed) current dose, individuals with high simulated current density at the target ROI (left dorsolateral prefrontal cortex) were found to have stronger improvements in working memory compared to those with low current density [21]. They also showed that individualizing the current dose by fixing the current density desired at the target region can maximize the benefits of tDCS [21]. Though the models are a step towards individualizing the current dose, they do not consider the spread of the field to intermediary (non-target) regions.…”

Section: Introductionmentioning

confidence: 98%

“…The current dose calculated through inverse modelling of tDCS induced electric field at the target ROI correlates with the motor thresholds generated by transcranial magnetic stimulation [15,16]. In a recent tDCS experiment using frontal montage and 2mA (fixed) current dose, individuals with high simulated current density at the target ROI (left dorsolateral prefrontal cortex) were found to have stronger improvements in working memory compared to those with low current density [21]. They also showed that individualizing the current dose by fixing the current density desired at the target region can maximize the benefits of tDCS [21].…”

Section: Introductionmentioning

confidence: 99%

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Focality Oriented Selection of Current Dose for Transcranial Direct Current Stimulation

Kashyap¹,

Bhattacharjee²,

Arumugam³

et al. 2021

Preprint

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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.

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Electric Field Strength From Prefrontal Transcranial Direct Current Stimulation Determines Degree of Working Memory Response: A Potential Application of Reverse-Calculation Modeling?

Cited by 36 publications

References 111 publications

A Systematic Review and Meta-Analysis of Transcranial Direct Current Stimulation to Remediate Age-Related Cognitive Decline in Healthy Older Adults

A Systematic Review and Meta-Analysis of Transcranial Direct Current Stimulation to Remediate Age-Related Cognitive Decline in Healthy Older Adults

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

Focality Oriented Selection of Current Dose for Transcranial Direct Current Stimulation

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