Realistic simulation of transcranial direct current stimulation via 3-d high-resolution finite element analysis: Effect of tissue anisotropy

Abstract

Recently, transcranial direct current stimulation (tDCS) is getting an attentions as a promising technique with a capability of noninvasive and nonconvulsive stimulation to treat ill conditions of the brain such as depression. However, knowledge on how exactly tDCS affects the activity of neurons in the brain is still not sufficient. Precise analysis on the electromagnetic effect of tDCS on the brain requires finite element analysis (FEA) with realistic head models including anisotropy of the white matter and the skull. In this paper, we have simulated tDCS via 3-D high-resolution FEA and investigated the effect of tissue anisotropy on tDCS. The results show that the skull anisotropy induces a strong shunting effect, causing a shift of the stimulated areas, and the white matter anisotropy affects strongly the current flow directions, changing the current field distribution inside the human brain. Our presented methodology and results should be useful for more effective guiding and treatment using tDCS.

Regional electric field induced by electroconvulsive therapy in a realistic finite element head model: Influence of white matter anisotropic conductivity

“…In the anisotropic model, all tissues except WM were assumed to be isotropic, since the WM has the most significant anisotropic microstructure (Geddes and Baker, 1967; Nicholson, 1965). Another tissue that is often treated as anisotropic is the skull (Fuchs et al, 2007; Marin et al, 1998; Rush and Driscoll, 1968; Suh et al, 2009; Suh et al, 2010). However, the effective skull anisotropy originates from the macroscopic skull structure consisting of a soft (spongiform) bone layer enclosed by two hard (compact) bone layers (Akhtari et al, 2002; Fuchs et al, 2007).…”

“…The representation of the head in computational ECT models ranges in detail from concentric spheres (Deng et al, 2009, 2011; Weaver et al, 1976) to low-resolution realistically-shaped representations (Bai et al, 2011; Sekino and Ueno, 2002, 2004) to high-resolution anatomically-accurate models (Nadeem et al, 2003; Szmurło et al, 2006). Furthermore, a substantial number of E-field/current density modeling studies have been published in the context of other transcranial electric stimulation paradigms, again ranging from simplified to realistic head representations (Datta et al, 2009; Datta et al, 2008; Grandori and Rossini, 1988; Holdefer et al, 2006; Im et al, 2008; Lee et al, 2009b; Miranda et al, 2007; Miranda et al, 2006; Nathan et al, 1993; Oostendorp et al, 2008; Parazzini et al, 2011; Rush and Driscoll, 1968; Sadleir et al, 2010; Salvador et al, 2010; Saypol et al, 1991; Stecker, 2005; Suh et al, 2009; Suh et al, 2010; Suihko, 2002; Wagner et al, 2007). However, these studies have various limitations.…”

“…Our and other groups have previously incorporated tissue anisotropic conductivity in models of electroencephalography and magnetoencephalography (Gullmar et al, 2006; Gullmar et al, 2010; Hallez et al, 2009; Hallez et al, 2008; Haueisen et al, 2002; Kim et al, 2003; Lee et al, 2008; Lee et al, 2009a; Marin et al, 1998; Rullmann et al, 2009; Wolters et al, 2006), transcranial direct current stimulation (tDCS) (Lee et al, 2009b; Oostendorp et al, 2008; Suh et al, 2009; Suh et al, 2010), deep brain stimulation (Butson et al, 2007), transcranial magnetic stimulation (TMS) (De Lucia et al, 2007; Thielscher et al, 2011), and electrical impedance tomography (Abascal et al, 2008). These studies demonstrate that anisotropic conductivity of the brain tissue can have a non-negligible effect on the electromagnetic field solutions.…”

Clinical research with transcranial direct current stimulation (tDCS): Challenges and future directions

“…On a final technical note: Though there has been a recent emphasize to develop increasingly accurate and complex models (89, 90, 93), certain universal technical issues should be considered for high-precision models, beginning with: 1) high-resolution (e.g. 1 mm) anatomical scans so that the entire model work flow should preserve precision.…”

Spatial and polarity precision of concentric high-definition transcranial direct current stimulation (HD-tDCS)

“…Typical configuration of 'conventional' tDCS comprises current delivery from a constant direct current stimulator using a 5 × 7 cm or 5 cm × 5 cm sponge pad-covered rubber electrodes (one anode and one cathode (1 × 1)) to the desired brain target. To overcome limitations in targeting with conventional tDCS (Baker et al 2010), the 4 × 1 concentric ring high-definition (HD) tDCS configuration (4 × 1 HD-tDCS) has been explored as an alternative montage (Datta et al 2009, Suh et al 2009, Edwards et al 2013 but (Borckardt et al 2009, Caparelli-Daquer et al 2012, Brunyé et al 2014, Roy et al 2014, Heimrath et al 2015, Nikolin et al 2015, Shekhawat et al 2016, Zito et al 2015, Castillo-Saavedra et al 2016, Flood et al 2016, Kuo et al 2013 we note that 4 × 1 deployment is only one HD configuration and others have been implemented (Dmochowski et al 2013, Kempe et al 2014, Donnell et al 2015, Xu et al 2015.…”