Physiological and modeling evidence for focal transcranial electrical brain stimulation in humans: A basis for high-definition tDCS

July 1, 2013

By Dylan Edwardsa, Mar Cortesa, Abhishek Dattae, Preet Minhase, Eric M. Wassermann,Marom Biksone

Brain stimulation experiments
Computational models
Validation of stimulation intensity: Subject-specific delivery of electric field intensity to motor cortex
Validation of stimulation focality: Targeting of the electric field within the 4×1-ring
Computational model: Low-intensity DC over the primary motor cortex

Abstract
Transcranial Direct Current Stimulation (tDCS) is a non-invasive, low-cost, well-tolerated technique producing lasting modulation of cortical excitability. Behavioral and therapeutic outcomes of tDCS are linked to the targeted brain regions, but there is little evidence that current reaches the brain as intended. We aimed to: (1) validate a computational model for estimating cortical electric fields in human transcranial stimulation, and (2) assess the magnitude and spread of cortical electric field with a novel High-Definition tDCS (HD-tDCS) scalp montage using a 4×1-Ring electrode configuration. In three healthy adults, Transcranial Electrical Stimulation (TES) over primary motor cortex (M1) was delivered using the 4×1 montage (4× cathode, surrounding a single central anode; montage radius ~3 cm) with sufficient intensity to elicit a discrete muscle twitch in the hand. The estimated current distribution in M1 was calculated using the individualized MRI-based model, and compared with the observed motor response across subjects. The response magnitude was quantified with stimulation over motor cortex as well as anterior and posterior to motor cortex. In each case the model data were consistent with the motor response across subjects. The estimated cortical electric fields with the 4×1 montage were compared (area, magnitude, direction) for TES and tDCS in each subject.

Physiological and modeling evidence for focal transcranial

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