## 4 Discussion
It can be concluded that no dependencies were found between the latency of MEPs themselves at the three investigated muscle condition tasks. It is worth noting again that only for the pairs between the latency of MEPs themselves, the degrees of uncertainty are detected. The last pair from case study 2, A_SP-C_SP, is in PsCo for all ten subjects (Table 7); hence, it can be summarized that there is evident consonance dependence between the durations of the silent periods themselves. We may presume, according to the combination of standard data processing and ICrA results, that our findings could be evidence that there is a lower level of excitability during the co-contraction of antagonist muscles than in reciprocal activity of the agonist muscle [33,41,42], and that in the cortical excitability are involved different nerve cell populations during different muscle condition tasks [43,44]. As can be seen from Table 8, which summarizes the results for case study 3, the most consonance relations (four) are found for TMS intensities 110% and 140% RMT. Three, two, and one consonance relations were found for TMS intensities, respectively, at 100%, 120%, and 130% RMT. Most of the criteria pairs are in PsCo, but there are also two pairs, namely, C_140 Ampl-C_140 SP and C_140 Lat-C_140 SP, detected in NgCo. It is interesting to note that the negative consonance results were only in pairs during the co-contraction condition at the highest TMS intensity. Figure 6: Number of consonance relations among themselves formed pairs of criteria at the three muscle conditions. ICrA found a consonance relation in PsCo between the amplitude of MEPs during abduction and co-contraction conditions for four of altogether five studied cases, namely for TMS intensities 100%, 110%, 130%, and 140% RMT (Figure 7a). This result is interesting because the recruitment curves were linear with a stable trend of increasing (Figure 3a), but from the literature, it is known that at 120-130% RMT are involved the maximal corticospinal structures. The individual 120% or 130% RMT stimulus intensity activates the maximal number of pyramidal tract structures and strong corticospinal projections to the motoneurons innervating the targeted muscle. This leads to the largest response to TMS and parameters of the evoked muscle responses (MEPs) reflect the sum of neural activity of corticospinal neurons [2; 3; 45; 46]. We suspect that positive consonance marked the differences between the pairs of MEP amplitudes, which reflect excitability structures involved in the different motor condition tasks. The standard data processing did not find any considerable differences, but there was a stable trend of increasing MEP amplitudes, and ICrA noticed it. The pair between the silent periods during abduction and co-contraction condition appeared in PsCo for TMS intensities 100%, 110%, and 120% RMT (Figure 7b). As mentioned before, 120% RMT stimulus intensity activates the maximal number of pyramidal tract structures. Due to SP, which is a result of the involvement of both excitable and inhibitory mechanisms, this could be a possible reason for the end of the trend in 120% RMT. We may assume that these PsCo results point to the differences between SP durations, which reflect inhibition structures involved in the different motor condition tasks. The standard data processing did not find any considerable differences, but there was a stable trend of increasing SP durations with the increase in TMS intensity and connected MEP amplitudes. One possible reason that at 130% and 140% RMT the ICrA results were not in consonance is the mixed individual results of the subjects. The mean values of group data formed linear curves (see Figure 3b) in which the conventional statistics did not find considerable changes. We assume that ICrA detects the specific changes in the data set that standard statistics cannot find. Figure 7: Criteria pair coincidences at different TMS intensities for (**a**) A_Ampl-C_Ampl, (**b**) A_SP-C_SP, (**c**) A_Lat-C_Lat, and (**d**) R_Lat-A_Lat.