There are no significant differences between the ages of the subjects in the real group (Mean = 28.54 SD = 6.28) and the sham group (Mean = 29.72 SD = 11.92).
Behavioral results. Comparing performance indices between phases and groups, we calculated the intervention effects on the task performance ability.
Mean RT at baseline was similar between the real and sham group (real group: Mean = 0.262s Standard Error (SE) = 0.072s; sham group: Mean = 0.282s SE = 0.069s; p > 0.5). In RT data, a significant main effect of Time F(4, 80) = 9.134 (p = .000), Group F(1,20) = 5.984 (p = .024) and interaction effect of Time x Group F(4,80) = 2.637 (p = .040) was found. At the post-hoc analysis (Bonferroni), the real group, compared to the Pre-assessment baseline state, significantly shortened RT in every time phase: first intervention (Mean = 0.128s SE = 0.019s, p = .000), second intervention (Mean = 0.159s SE = 0.026s, p = .001), post assessment (Mean = 0.194s SE = 0.022s, p = .008) and the post-30-minutes assessment (Mean = 0.169s SE = 0.025s, p = .001). Compared to first intervention time, the RT in post assessment time significantly augmented (p = .006).
Regarding the sham group, it significantly shortened the RT score compared to the baseline only in the post-30-assessment time (Mean = 0.172s SE = 0.022s, p = .009).
The real TMS group reduced significantly the RT compared with the sham group (sham group: Mean = 0.245s SE = 0.019s, p = .000) in the first intervention phase (D = 0.117s, SE 0.026s) (Fig. 3).
Regarding the TE, real and sham group significantly improved their adjustments to the trajectory through time. A significant main effect in Time F(4,80) = 34.59 (p = .000) was found while no significant differences were found between groups (REAL: Pre, 1.52; Int1, 1.20; Int2, 1.19; Post, 1.15; Post30, 1.08; SHAM: Pre, 1.78; Int1, 1.45; Int2, 1.32; Post, 1.28; Post30, 1.19). Concerning collected items variable in task performance, both groups significantly changed overtime. A significant main effect in Time F(4, 80) = 54.48 (p = .000) was found. However, no changes between groups were observed (REAL: Pre, 10.05; Int1, 11.50; Int2, 12.01; Post, 12.36; Post30, 12.75; SHAM: Pre, 9.23; Int1, 10.50; Int2, 11.25; Post, 11.70; Post30, 11.93). Moreover, in avoided item index a significant main effect in Time F(4, 80) = 18.36, p = .000 was found as well, although no significant differences were seen between groups (REAL: Pre, 1.23; Int1, 0.79; Int2, 0.72; Post, 0.74; Post30, 0.66; SHAM: Pre, 1.29; Int1, 0.93; Int2, 0.76; Post, 0.82; Post30, 0.68). All with p > 0.05.
To summarize, the obtained results demonstrate that, since the first intervention, the real group has been able to perform shorter RTs. Compared to the sham group, the first TMS application time generated a significant difference in task performance. The time-accuracy movement learning was immediate when applying TMS.
Cortico-spinal excitability. The Mean ± SE of data for both muscles in separated condition groups are represented in Fig. 4.
Firstly, we normalized the data and analyzed it by a three intra-subject factors (Muscle, Time, and Intensity) and one inter-subject factor (Group condition) ANOVA. A significant main effect of Muscle (F(1, 20) = 7.855, p = .011); Time (F(3, 60) = 3.565, p = .019); and Intensity (F(4, 80) = 298.606, p = .000) was found, as well as Muscle x Intensity (F(4, 80) = 6.456, p = .000); Time x Intensity (F(12, 240) = 2.483, p = .004); Muscle x Time x Intensity x Group (F(12, 240) = 3.030, p = 0.001).
The post-hoc pair comparison with Bonferroni correction for multiple comparison revealed that in the real group at PrePre-assessment time, the APB muscle MEP amplitude induced at 130% of RMT (Mean = 2.456 SD = 0.388) was significantly higher than in Post-assessment time (Mean = 0.977 SD = 0.263, p = .021). In contrast, at Post-assessment time of the ADM muscle MEP amplitude induced at 110% of RMT (Mean= -0.451 SD = 0.102) was significantly lower than in Post-30’-assessment (Mean = 0.056 SD = 0.197, p = .047). There are not significant differences between time phases in the sham group.
These results indicate that the TMS intervention synchronized with the dynamic task movement was depressing the motor excitability in the target APB muscle right after the task at 130 % RMT intensity and inducing an opposite mechanism enhancing motor excitability of the control ADM muscle in a long lasting manner, at 110% RMT intensity.
Correlation between behavior performance and cortico-spinal excitability changes induced by TMS-PAS application. The application of MRCS PAS induced changes in motor performance as well as in the excitability levels of motor cortico-spinal pathway. The correlation between these two different changes will explain the same induction from TMS intervention or the possible causality relation between the factors.
As far as the real group concerns, we found positive lineal correlations (Fig. 5) between the RT of the first intervention time (the significantly different RT condition between groups) and the MEP amplitude induced in ADM muscle in Post-assessment time at 110% of RMT intensity (r = 0.775, p = .008 ) and 130% of RMT intensity (r = 0.668, p = .035 ), as well as in Post30-assessment time at 130% of RMT intensity (r = 0.634, p = .049 ). This indicated that the lower is the MEP amplitude in ADM muscle, the shorter the RT.
Regarding the same comparison in sham group (Fig. 6), a tendency for negative lineal correlation was observed between the RT of the first intervention time and the amplitude of MEP induced in ADM muscle in Post-assessment time at 110% of RMT intensity (r=-0.495, p = .122), at 130% of RMT intensity (r=-0.575, p = .064) and in Post-30’-assessment time at 130% of RMT (r=-0.559 p = 0.074).
No correlation was found comparing the RT of first intervention time with APB MEPs. No other correlations between RT and MEP amplitude of the same time were found.