## 4 Discussion
Therefore, we might be able to conclude from previous research that: first, perceived lengths between fingertips and metacarpophalangeal joints were shorter than real lengths; second, perceived lengths between metacarpophalangeal joints and the wrist were longer than real lengths. However, the perceived lengths of the whole hand remained unclear. Our result showed for the first time that the perceived length of a hand was shorter than the real hand. In addition, perceived wrist length was not influenced by rPMS and was close to real wrist length, which might be attributed to the experimental settings where the forearm could be seen during the experiment. However, the function of perceiving the wrist joint was that it provided a baseline and reference for perceiving the fingertips in a systematic order, which could contribute to more accurate judgements [36]. To sum up, we adopted six landmarks rather than ten landmarks in this study as a modified paradigm for measuring the perceived lengths of the whole hand, which might facilitate future experimental or practical applications. Our study observed a short-lasting effect of rPMS on implicit body representation of the hand. In the real rPMS group, before stimulation compared with right after stimulation and 10 min after stimulation, the enlargements of implicit body representation of the hand were not so obvious; however, before stimulation compared with 20 min after stimulation, the enlargement effect was statistically significant. [PERSON] et al. found that with transcranial magnetic stimulation as a detection method, single and paired pulse motor evoked potential (MEP) recruitment curves were increased post-stimulation up to 1 h and intracortical facilitation was increased up to 30 min [25]; however, they adopted 20 min of 25 Hz rPMS application which was supposed to have longer-lasting effect than in this study. [PERSON] et al. also demonstrated that a significant increase in MEP was observed up to 60 min following 15 min of 50 or 25 Hz rPMS [41]. [PERSON], [PERSON] et al. found that single-session 20 Hz rPMS could modulate corticomotor excitability by measuring MEP, together with a possible lasting improvement in hand dexterity [42]. We observed a 20 min lasting effect of single-session 50 Hz rPMS on implicit body representation of the hand, which is in accordance with the above research. This study researched the implications of implicit body representation of the hand in the progress of neurorehabilitation practice. It has been reported that goggles maximize or minimize vision, which can affect the perceived size of certain objects by healthy participants; however, this effect was reduced when participants placed their hands beside the object, even though the visual size of their own hands was also enlarged or shrunk by the goggles [43]. This finding indicates that representation of the hand in the mind plays a calibration role when humans interact with the surrounding environment. The visual hand size being maximized or minimized by the goggle did not affect the calibration role of the participants' real hand. In other words, it might be the implicit body representation of the hand that was not affected by the goggles, which undertook the important function of calibration. Since implicit body representation of the hand was enlarged by rPMS within the boundary of a real hand, we wonder whether the calibration function of the hand could be strengthened as well. Our next study project is to explore the correlations between hand functions and implicit body representation, both in healthy adults and chronic stroke patients, in order to develop new neurorehabilitation therapies based on implicit body representation. This study had some limitations. First, we adopted only single-session rPMS with 36 trials, and because this is a pilot study to our knowledge, it is not clear whether there is a difference in the plastic change in implicit body representation of the hand after multi-session or long-term application of rPMS from what we observed in this study.