Cost of focality in TDCS: Interindividual variability in electric fields

In transcranial direct current stimulation (TDCS), electric current is applied via two large electrodes to modulate brain activity. Computational models have shown that large electrodes produce diffuse electric fields (EFs) in the brain, which depends on individual head and brain anatomy. Recently, smaller electrodes as well as novel electrode arrangements, including high-definition TDCS (HD-TDCS) montages, have been introduced to improve the focality of EFs. Here, we investigated whether the EFs of focal montages are more susceptible to interindividual anatomical differences.