Transcranial direct current stimulation (tDCS) in a realistic head model

Impact of tDCS on performance and learning of target detection: Interaction with stimulus characteristics and experimental design

“…While we targeted the right frontal cortex, it is unlikely that tDCS resulted in focal stimulation of the brain, and may have included other brain regions as well. While there are no modeling studies that simulate the placement of the anode on the right frontal cortex with a cathode on the left upper arm, other studies indicate that even with two electrodes placed on the scalp the stimulation is diffuse and unpredictable (Datta et al, 2009;Miranda et al, 2009;Sadleir, Vannorsdall, Schretlen, & Gordon, 2010;Wagner, Valero-Cabre, & Pascual-Leone, 2007). Realistic, finite element head models suggest that a large fraction of the current passes into the brain via low resistance paths including the orbits and nose (Sadleir et al, 2010).…”

“…While there are no modeling studies that simulate the placement of the anode on the right frontal cortex with a cathode on the left upper arm, other studies indicate that even with two electrodes placed on the scalp the stimulation is diffuse and unpredictable (Datta et al, 2009;Miranda et al, 2009;Sadleir, Vannorsdall, Schretlen, & Gordon, 2010;Wagner, Valero-Cabre, & Pascual-Leone, 2007). Realistic, finite element head models suggest that a large fraction of the current passes into the brain via low resistance paths including the orbits and nose (Sadleir et al, 2010). Though there are no empirically based methods currently accepted to identify the precise path of tDCS current through the brain, magnetic resonance spectroscopy based methods to image tDCS induced changes in glutamatergic activity and other metabolites are currently being developed .…”

Measurements and models of electric fields in the in vivo human brain during transcranial electric stimulation

“…Current-flow modeling approaches range from spherical models (Rush and Driscoll, 1969;Ferdjallah et al, 1996;Stecker, 2005;Miranda et al, 2006;Datta et al, 2008;Dmochowski et al, 2012) to more realistic individualized models derived from MRI (Wagner et al, 2004;Datta et al, 2009;Sadleir et al, 2010;Parazzini et al, 2011;Minhas et al, 2012;Datta et al, 2010;Wagner et al, 2007). Individualized modeling implies the need to consider the anatomy of individual subjects , in particular for patient populations that may have abnormal brain anatomy Dmochowski et al, 2013).…”

“…For instance, fatty tissue has been modeled by Truong et al (2013), who suggested that electric fields are altered in particular for obese individuals. Other details that may be important are muscle, arteries, sub-compartments of the eyes, and other anatomical details (Sadleir et al, 2010;Parazzini et al, 2011;Mekonnen et al, 2012). A general sense for the sensitivity of the model accuracy to errors in segmentation can be obtained by comparing the prediction performance of the intact models and the realistic models (IM vs. RM in Figure 9).…”

“…Unfortunately, despite increasing sophistication in these computational models (Wagner et al, 2004;Datta et al, 2009;Sadleir et al, 2010;Parazzini et al, 2011;Datta et al, 2012;Minhas et al, 2012;Datta et al, 2010;Wagner et al, 2007;Datta et al, 2011;Dmochowski et al, 2013;Luu et al, 2016), none of these model predictions have been directly validated to-date. Early validation efforts for simple spherical models used ex vivo recordings (Rush and Driscoll, 1968), surface recordings (Burger and Milaan, 1943) or in vivo recordings in simian (Hayes, 1950).…”