Longitudinal and transverse conductivity of WM tensor elements calculated using the artificial anisotropy with volume constraint according to anisotropic factors (r).

<p>Longitudinal and transverse conductivity of WM tensor elements calculated using the artificial anisotropy with volume constraint according to anisotropic factors (r).</p

Schematic view of the neuronal model morphology and placement.

<p>Orientations of layer 3(L3) and layer 5(L5) pyramidal neuronal models are shown, with bends in different locations. They represent only one aspect of the uniform neuronal models.</p

The relative ratio of the number of L5 neurons excited for three polarities.

<p>The six different anisotropic models were compared.</p

The minimum excitation thresholds (mA) of L5 neurons in the anatomically realistic head model over the six anisotropic models; parentheses indicate the location of neuron(s) excited: crown (C) and bank (B).

<p>The minimum excitation thresholds (mA) of L5 neurons in the anatomically realistic head model over the six anisotropic models; parentheses indicate the location of neuron(s) excited: crown (C) and bank (B).</p

Conductivities of tissues and electrodes [15,18,47,48].

<p>Conductivities of tissues and electrodes [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0128590#pone.0128590.ref015" target="_blank">15</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0128590#pone.0128590.ref018" target="_blank">18</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0128590#pone.0128590.ref047" target="_blank">47</a>,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0128590#pone.0128590.ref048" target="_blank">48</a>].</p

The shape of the anatomically realistic head model.

<p>(a) Whole head model and (b) cross-section of head model for subdural cortical stimulation are shown. Red and blue dots on the cortex represent implanted electrodes.</p

Comparison between isotropic and anisotropic conductivity for anodal, cathodal and bipolar stimulation.

<p>(a) Electrode placement in the anatomically realistic head model. Inset represents the ROI, including the crown (C), lip (L) and bank (B) on the GM. (b) The spatial extent of the excitation thresholds for L3 and L5 neurons between the isotropic and anisotropic models over three polarities.</p

Comparison among various anisotropic conductivities for anodal, cathodal and bipolar stimulation.

<p>Spatial extents of excitation thresholds of L5 neurons are shown in various anisotropic models within the ROI shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0128590#pone.0128590.g004" target="_blank">Fig 4(A)</a>.</p

Placement of L5 and L3 pyramidal neuronal models in the anatomically realistic head model.

<p>Locations of L5 and L3 somata are marked as colored dots (blue: L5, red: L3) in cross-section passing through two electrodes.</p

The relative ratio (%) of neurons excited with stimulation at three different polarities (anodal (A), cathodal (C), and bipolar (B) stimulation).

<p>L5 and L3 neurons in the anatomically realistic head model were compared between the isotropic (iso) and anisotropic (aniso) models.</p