Using Transcranial Magnetic Stimulation to Improve Motor Cortical Excitability During Motor Imagery

External stimulation, such as transcranial magnetic stimulation (TMS), is considered a technique to improve motor cortical excitability during motor imagery (MI). However, few studies have examined the effects of TMS on motor intention during MI and the effects of TMS combined with MI on cortical plasticity. For this, we randomly enrolled 18 healthy young people, divided them into two groups (nine people in each group), and conducted two types of experiments: an MI experiment (MI group) and a TMS during the MI experiment (MI + TMS group). We also calculated the
$\mu $
-event-related desynchronization (
$\mu $
-ERD), MI accuracy, and functional connectivity, and compared changes in these measures before and after the training. The results showed that compared with the MI group, the
$\mu $
-ERD, MI recognition rate, and the local-scale functional connectivity of both hemispheres in the MI + TMS group were significantly improved. However, further analysis of the power spectrum density of the EEG signals showed that some subjects in both groups had obvious mental fatigue, which compromised the effect of TMS in MI. We conclude that TMS during MI can improve cortical cortex plasticity, increase motor intention, and improve the MI decoding rate. This research lays the foundation for applying MI combined with TMS in rehabilitation training and BCI system.