Dependency of the tDCS-induced effects on baseline functional architecture.

<p>Panel A shows that the effect of nodal clustering coefficient (<i>C</i>) increase found in the cluster of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030971#pone-0030971-g003" target="_blank">Figure 3F</a> strongly correlated with baseline <i>C</i> (P = 0.0051; R² = 0.46). Panel B shows that the positive decrease found in the characteristic path length (<i>L</i>) maps that was found after anodal tDCS (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030971#pone-0030971-g003" target="_blank">Figure 3H</a>) also has a positive correlation with the baseline <i>L</i> (P = 0.002; R² = 0.51).</p

Global network metrics.

<p>Shown are the results of the global network parameters that were calculated in the present study (mean connectivity degree (<i>K</i>) and the small-world parameters gamma, lambda and sigma <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030971#pone.0030971-Sporns2" target="_blank">[32]</a>) calculated at each threshold T (0.25–0.35 in increasing steps of 0.002) before and after each Sham (A), Cathodal (B) and Anodal (C) tDCS. The second row - second column of each panel show that the approximate number of nodes (M1 voxels) of each undirected graph was ∼470. As expected, the mean connectivity degree monotonically decreases as <i>T</i> increases. M1 has salient small-world properties i.e. <i>lambda≈1</i>, <i>gamma≫1</i>, thus <i>sigma≫1 </i><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030971#pone.0030971-Sporns2" target="_blank">[32]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030971#pone.0030971-Achard1" target="_blank">[41]</a>. No significant differences were observed for any of the network metrics before and after each of the tDCS sessions (P>0.05 paired two-tailed t-tests). Error bars represent the s.e.m.</p

Regions of decreased activity for hf-tRNS.

<p>Contrast <i>sham- Hfreq</i> (A) revealed changes in the left frontal cortex. Contrast <i>Lfreq-Hfreq</i> (B) revealed additional changes in right frontal cortex and precuneous.</p

Performance related decrease of brain activity during and after stimulation.

<p>Activity decreased with time for contrast <i>run1-run2</i> in the paracingulate gyrus, superior frontal gyrus, thalamus and hippocampus. (Z>3, P<0.05, corrected).</p

Changes in tracking error relative to the first trial.

<p>Shaded area corresponds to the stimulation period. Fifth Polynomial trendlines are superimposed on the data for easier visualization.</p

Motor task-related decrease of brain activity during and after stimulation.

<p>Activity decreased with time for contrasts <i>run1-run2</i> (A) in primary and premotor cortices, supplementary motor area (SMA), prefrontal cortex, occipital cortex, thalamus and basal ganglia and <i>run2-run3</i> (B) in the precuneous, superior parietal cortex, middle and inferior frontal gyrus, right prefrontal cortex, left inferior LOC and basal ganglia (Z>3, P<0.05, corrected).</p

Cross coil experiments.

<p>a) A photograph of the cross coil used in the experiment. The two coils interlock on perpendicular planes and connect to two independent stimulators. b) A photograph of the glass sphere that was custom made to fit inside the cross coil. The glass coverslip, on which the neuronal culture grows, and the fluid medium were inserted through a slot located at the top of the sphere. The coverslip lay on a flattened base at the bottom of the sphere and was observed via a viewing aperture, which was sealed with optically transparent glass. See also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0086794#pone.0086794.s003" target="_blank">Video S1</a>. c) Schematic of the setup – the coverslip (red) was placed in a glass sphere inside the cross coil while an inverted epi-fluorescence microscope monitored neuronal activity. Scale bars in a–c are <i>2 cm</i>. d) Cross coil setup for rat experiments. The rat's head was positioned inside the cross coil (in place of the glass sphere, which was not used). EMG electrodes recorded muscle potentials from the Gastrocnemius. The EMG data was digitized and synchronized with the rfTMS pulses to assess the motor response to rfTMS. e) The induced electric field in the cross coil was measured using a pick-up coil oriented first on the plane of one of the coils (solid line) and then on the plane of the second coil (dashed line). The Magstim stimulator was loaded to <i>100%</i> and the HMS was loaded with <i>3.5 kV</i> (see details in the Methods section). f) A reconstruction of the effective electric field created from the sum of the two perpendicular components measured in e) with the field of coil #1 directed along the x-axis and the field of coil #2 along the y-axis. The effective field was reconstructed for a specific location just inside the poles of the cross coil (‘Neuronal culture’ arrow in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0086794#pone-0086794-g002" target="_blank">Figure 2d</a>). The effective field completes <i>¾</i> of a spiral cycle during the magnetic pulses cycle, as indicated by the black arrows.</p