Figure 3: Behavioural indices recorded in Experiment 1.

(a) maintenance: time spent keeping a key pressed, which shows the treatment significantly increases the ability of the patient to maintain a selection (t(20) = 2.62, p = 0.016); (b) perseverance: time required to disengage from a selection after each change of luminance pattern on the screen, which shows the treatment significantly increases the chances the patient will persevere in any selection (t(20) = 2.14, p = 0.045); (c) number of changes of selection or switches, per luminance pattern, which does not show a significant effect of treatment (t(20) = −1.4648, p = 0.16). Histograms represent mean measures and standard deviation, per trial, under on- and off- subthalamic stimulation. Triangular markers represent mean values per participant, under each condition. The distribution in quartiles of within subject differences, per measure, is represented in the boxplots. Statistical significance (T test comparisons) expressed as follows: **for p ≤ 0.01; *for 0.05 > p ≥ 0.01; ^(ns) for not significant.