Addressing transcranial electrical stimulation variability through prospective individualized dosing of electric field strength in 300 participants across two samples: the 2-SPED approach

• Published in: Journal of neural engineering Vol. 19; no. 5; pp. 56045 - 56055
• Main Authors: Van Hoornweder, Sybren, A Caulfield, Kevin, Nitsche, Michael, Thielscher, Axel, L J Meesen, Raf
• Format: Journal Article
• Language: English
• Published: England IOP Publishing 01.10.2022
• Subjects: Adult; Brain - physiology; computational dosimetry; electric field (E-field) modeling; finite element method (FEM); Humans; noninvasive brain stimulation; transcranial direct current stimulation (tDCS); Transcranial Direct Current Stimulation - methods; transcranial electrical stimulation (tES); transcranial electrical stimulation (tES); computational dosimetry; finite element method (FEM); electric field (E-field) modeling; transcranial direct current stimulation (tDCS); noninvasive brain stimulation
• ISSN: 1741-2560; 1741-2552; 1741-2552
• DOI: 10.1088/1741-2552/ac9a78

Objective . Transcranial electrical stimulation (tES) is a promising method for modulating brain activity and excitability with variable results to date. To minimize electric (E-)field strength variability, we introduce the 2-sample prospective E-field dosing (2-SPED) approach, which uses E-field strengths induced by tES in a first population to individualize stimulation intensity in a second population. Approach . We performed E-field modeling of three common tES montages in 300 healthy younger adults. First, permutation analyses identified the sample size required to obtain a stable group average E-field in the primary motor cortex (M1), with stability being defined as the number of participants where all group-average E-field strengths ± standard deviation did not leave the population’s 5–95 percentile range. Second, this stable group average was used to individualize tES intensity in a second independent population (n = 100). The impact of individualized versus fixed intensity tES on E-field strength variability was analyzed. Main results . In the first population, stable group average E-field strengths (V/m) in M1 were achieved at 74–85 participants, depending on the tES montage. Individualizing the stimulation intensity (mA) in the second population resulted in uniform M1 E-field strength (all p < 0.001) and significantly diminished peak cortical E-field strength variability (all p < 0.01), across all montages. Significance . 2-SPED is a feasible way to prospectively induce more uniform E-field strengths in a region of interest. Future studies might apply 2-SPED to investigate whether decreased E-field strength variability also results in decreased physiological and behavioral variability in response to tES.