## 4 Discussion
The TMS-A_SP and TMS-C_SP pairs fall into PsCo for all subjects, while the pairs A_Ampl-A_SP and C_Ampl-C_SP are simultaneously in dissonance for S1 and S2. Results of ICrA are in line with the general dependence that silent period duration is influenced by the stimulus intensity, and also high MEP amplitudes resulting in longer SP [33; 34; 35; 36; 37]. Also, as known from the literature [3], the duration of the cortical silent period evoked by a single suprathreshold stimulus intensity may be used as a measure of GABAB\({}_{\text{B}}\)-ergic inhibition. The results for S1 and S2 are connected with those mentioned before about individual subject characteristics of EMG activity and responses to TMS, which were not pointed out by the conventional statistics. However, we should note that SP duration is directly related to the voluntary contraction [32; 33; 34; 35; 36]. It is thought that behavioral and cognitive factors can influence SP duration, as well as motor and non-motor neurological disorders [2; 37; 3]. The pair TMS-R_Lat found at the relaxed condition is an interesting exception. For this pair, ICrA outlines altogether six consonance relations as presented in Figure 4. Four results are in PsCo (for subjects S3, S8, S9, S10), two in NgCo (S4, S5), and four in dissonance (for subjects S1, S2, S6, S7). In general, it can be concluded that there is a consonance relation for the TMS-R_Lat, but the results should be interpreted carefully until further investigations confirm this finding. For the remaining pairs of criteria (TMS-A_Lat; TMS-C_Lat; R_Ampl-R_Lat; A_Ampl-A_Lat; C_Ampl-C_Lat; A_Lat-A_SP; C_Lat-C_SP), no clearly defined relations were observed. It is obvious that MEP latencies are involved in all mentioned pairs. Also, it should be noted that only for the pairs that included MEP latency was there the uncertainty \(\pi\) calculated for some of the subjects (the results are not shown here, but for completeness are discussed). As proposed in [38], the reason could be some equal values of MEP latency at different TMS intensities for these subjects. Some authors found that individual MEP latencies vary considerably from trial to trial, and this variation is continuous and is accompanied by a systematic covariation in MEP amplitude, as larger MEP amplitudes are associated with shorter latencies [39] and higher stimulus intensities [5]. The amplitude and latency of MEP provide a direct measure of corticospinal excitability. A larger MEP  
Figure 5: Recruitment curves of: (**a**) S4, (**b**) S1, and (**c**) S2. amplitude may signify greater cortical excitability, while a longer MEP latency may be associated with decreased cortical excitability [2,4,40], but intraindividual and interindividual differences in excitability must be noted. The biological relevance of interindividual differences in TMS-evoked measurements shows that variations in cortical myelination are connected to differences in corticomotor hotspot location and motor control precision [4,35]. Nevertheless, in standard data processing, we did not find a considerable connection between the pairs, stimulus intensity-MEP latency, MEP amplitude-MEP latency, and MEP latency-SP duration, verified also after ICrA application, with only one exception for the TMS-R_Lat pair at the relaxed muscle condition. For better interpretation of the ICrA results from case study 2, Figure 6 presents a summarized number of consonance relations for each pair of criteria at the three muscle conditions. As shown in Figure 6, the results obtained from case study 2 reveal that the pairs R_Ampl-A_Ampl and R_Ampl-C_Ampl are in PsCo for six out of ten subjects, while the pair A_Ampl-C_Ampl is in PsCo for eight out of ten subjects (Table 5). There was a clear consonance relation in PsCo for the amplitude of MEPs themselves. As can be expected, most of the results for the pairs R_Lat-A_Lat, R_Lat-C_Lat, and A_Lat-C_Lat are in dissonance (Table 6). Moreover, only for the pair A_Lat-C_Lat, there is no one consonance relation.