Fig. 2.

Differential effects of levodopa medication and deep brain stimulation (DBS) in the subthalamic nucleus (STN) on functional connectivity in motor networks affected by Parkinson's disease. The upper row shows Eigenvector Centrality (EC) differences between both treatment states when comparing levodopa medication (PRE_ON) with DBS of the left and right STN (POST_{ON_left} and POST_{ON_right}). Using the contrasts POST_{ON_left}−PRE_ON and POST_{ON_right}−PRE_ON (color-coded in magenta and red, respectively; overlap in yellow), we found increased EC with both left and right unilateral DBS compared with levodopa medication (see Table 2 for coordinates, cluster sizes, and statistical values). The second row shows the result for the same analysis comparing both OFF-conditions using the contrast POST_OFF−PRE_OFF. The bottom row shows the interaction between both factors PRE/POST and OFF/ON using the contrast including the difference of difference (POST_{ON_left}−PRE_ON)−(POST_OFF−PRE_OFF) and (POST_{ON_right}−PRE_ON)−(POST_OFF−PRE_OFF) (color-coded in magenta and red, respectively; overlap in yellow). The figure shows EC values with the ‘add’ approach (for the other approaches ‘pos’ and ‘abs’, see Figs. S1 and S2 in the Supplementary material).