## 4 Discussion  
The main finding of this study was that single-session real rPMS compared with sham rPMS had an enlargement effect on implicit body representation of the hand in general, which might be attributed to the proprioception input induced directly and indirectly by real rPMS. When the motor branch of the radial nerve was activated by magnetic stimulation, there were two possible proprioception inputs from the peripheral body to the central nervous system; one was generated by the radial nerve and conveyed directly from the stimulation site through the radial nerve; the other was produced by the extension movements of wrist joint and fingers secondary to magnetic stimulation, then uploaded to the brain [32,33]. Therefore, our hypothesis was validated that by inducing the extension movements of the wrist joint and fingers, proprioception was inputted contributed to the enlargement of implicit body representation of the hand. Further, this enlarged implicit body representation of the hand was still within the boundary of a real hand. As mentioned in the introduction, local anesthesia can also enlarge implicit body representation of the mouth, beyond the boundary of a real mouth. Combined with these findings, we propose that intact and even enhanced implicit body representation is conservative within the boundary of a real body part, while loss of real-time somatosensory information input (mainly the proprioception) makes the conservative implicit body representation hard to maintain, thus overshooting the boundary of a real body part. Recent research also supports the above interpretation that perceptual distortion of the mouth was larger after local anesthesia, and after repetitive transcranial magnetic stimulation applied to the mouth representation area of somatosensory cortex, the overshooting perceptual distortion decreased to approaching the original perceived size, even though this Intervention was given directly to the brain [34]. We noticed that this enlargement effect was significant in the ulnar-side fingers. In this study, perceived hand lengths of where the ring and little finger locate, and the percentages of perceived hand lengths of where the middle, ring and little finger locate to their corresponding real lengths were enlarged by rPMS. This result was in accordance with previous research [18,35] that the percent overestimation of perceived finger length was observed in healthy adults, decreasing from the radial to the ulnar side of the hand. Figure 3: In the real rPMS group, the perceived hand length of where the ring finger locates before stimulation compared with 20 min after stimulation the enlargement had statistical significance, see **left panel**. In the real rPMS group, the percentage of the perceived hand length of where the ring finger locates to corresponding real length before stiSchememulation compared with 20 min after stimulation the enlargement had statistical significance, see **right panel. ** * represents \(p\) value \(<\) 0.0167. This enlargement effect was especially significant in the ring finger rather than in the little finger, which might be because the thumb and index finger are used more frequently in people's daily life and work and have a relatively bigger somatosensory cortex areas in the brain, while the little finger is the least used finger and occupies a relatively smaller somatosensory cortex area; therefore, a bigger somatosensory cortex might be able to deal with a higher resolution of input signals that form more accurate body representation of the corresponding body part [36]. Former research demonstrated that the perceived lengths of the five fingers were shorter than for real fingers [18; 37; 38], findings which were consistent with our results. Moreover, in another research paradigm of a knuckle localization task, perceived positions of knuckles were farther forward than real positions of participants' hands [39; 40].