Standard Non-Personalized Electric Field Modeling of Twenty Typical tDCS Electrode Configurations via the Computational Finite Element Method: Contributions and Limitations of Two Different Approaches

Abstract

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation procedure to modulate cortical excitability and related brain functions. tDCS can effectively alter multiple brain functions in healthy humans and is suggested as a therapeutic tool in several neurological and psychiatric diseases. However, variability of results is an important limitation of this method. This variability may be due to multiple factors, including age, head and brain anatomy (including skull, skin, CSF and meninges), cognitive reserve and baseline performance level, specific task demands, as well as comorbidities in clinical settings. Different electrode montages are a further source of variability between tDCS studies. A procedure to estimate the electric field generated by specific tDCS electrode configurations, which can be helpful to adapt stimulation protocols, is the computational finite element method. This approach is useful to provide a priori modeling of the current spread and electric field intensity that will be generated according to the implemented electrode montage. Here, we present standard, non-personalized model-based electric field simulations for motor, dorsolateral prefrontal, and posterior parietal cortex stimulation according to twenty typical tDCS electrode configurations using two different current flow modeling software packages. The resulting simulated maximum intensity of the electric field, focality, and current spread were similar, but not identical, between models. The advantages and limitations of both mathematical simulations of the electric field are presented and discussed systematically, including aspects that, at present, prevent more widespread application of respective simulation approaches in the field of non-invasive brain stimulation.

Optimized APPS-tDCS electrode position, size, and distance doubles the on-target stimulation magnitude in 3000 electric field models

“…This approach mirrors Datta et al’s (2009) development of 4 × 1 high definition (HD)-tDCS, in which E-field modeling demonstrated how HD-tDCS produces more focal stimulation prior to human application 43 . Similarly, here we used E-field modeling to provide a theoretical basis for tDCS electrode optimization, building on prior work demonstrating that tDCS electrode positioning matters 44 , 45 , and that the highest E-field is often midway between electrodes 34 , 46 . Drawing on this concept, Mikkonen et al (2020) designed conventional tDCS with electrodes placed with the target in the middle 47 .…”

A map of evidence using transcranial direct current stimulation (tDCS) to improve cognition in adults with traumatic brain injury (TBI)

“…Despite adequate design methods, current tDCS research for TBI-related cognitive impairments provides only preliminary insights supporting that tDCS may improve physiologic and behavioral cognitive function after TBI. Importantly, these results support that it is safe, inexpensive, and prudent to further research the use of tDCS for cognition across all TBI acuities and severities using biomarkers including electrical-field modeling (Evans et al, 2020 ; Molero-Chamizo et al, 2021 ; Mizutani-Tiebel et al, 2022 ; Nasimova and Huang, 2022 ).…”

The impact of prefrontal transcranial direct current stimulation (tDCS) on theory of mind, emotion regulation and emotional‐behavioral functions in children with autism disorder: A randomized, sham‐controlled, and parallel‐group study

“…To obtain more detailed data about the location of the effects, stimulation protocols which allow more specific targeting of only the left, or right DLPFC would be warranted in future studies. A relevant point to consider here is that we used 5 × 5 cm, and such relatively large electrodes, which likely affect also brain areas beyond the left and right DLPFC, as suggested by computational modeling studies (Molero‐Chamizo et al, 2021; Salehinejad, Nejati, Mosayebi‐Samani, et al, 2020). Respective mechanisms should be explored directly in future studies with a design that can compare the specific contribution of the left, right and both DLPFC, and physiological measures such as neuroimaging methods.…”